Merge branch 'wt-fix-0102-base'

The bare-fn-as-value site (func_ref / fn-ptr / closure coercion) eagerly
lazily-lowered the name-keyed first-wins WINNER before the resolveBareCallee
block could reroute a genuine flat same-name collision to its per-source
author. Taking a SHADOW author's fn value therefore lowered (and could
mis-diagnose) the unused winner's body. Move lazyLowerFunction INSIDE blk_fv
onto the `.none` fallback only, mirroring the closure(fn) and free-function
UFCS sites: on `.func` use the resolved author's FuncId and never touch the
winner; on `.none` fall through to lazy-lower + resolveFuncByName the winner.

Regression: examples/0735-modules-flat-same-name-fn-value-winner — the
first-wins winner's body is independently broken and never used; a shadow
taken as a function value binds the shadow and runs (exit 0) while the winner
is not lowered. Fails-before (unresolved symbol in the winner), passes-after.

examples/0722-modules-flat-same-name-own.sx

@@ -0,0 +1,18 @@
+// fix-0102c (issue 0102): two flat FILE imports each author a same-name free
+// function `greet`. The first-wins import merge keeps exactly one `greet` in
+// the merged scope, but each module's OWN code must bind its OWN author when it
+// calls `greet` bare. `from_a` (in a.sx) returns 1; `from_b` (in b.sx) returns
+// 2 — per-source binding, resolved by identity, not first-wins.
+#import "modules/std.sx";
+#import "0722-modules-flat-same-name-own/a.sx";
+#import "0722-modules-flat-same-name-own/b.sx";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("from_a binds a.greet", from_a() == 1);
+    report("from_b binds b.greet", from_b() == 2);
+    0
+}

examples/0722-modules-flat-same-name-own/a.sx

@@ -0,0 +1,5 @@
+// a.sx authors `greet`. Its own `from_a` calls `greet` bare — under fix-0102c
+// that binds a.sx's OWN author (own-author wins), even though b.sx also
+// authors `greet` and the first-wins merge keeps only one in the merged scope.
+greet  :: () -> s64 { return 1; }
+from_a :: () -> s64 { return greet(); }

examples/0722-modules-flat-same-name-own/b.sx

@@ -0,0 +1,4 @@
+// b.sx authors its OWN `greet`. `from_b`'s bare `greet` must bind b.sx's
+// author (2), not the first-wins winner from a.sx.
+greet  :: () -> s64 { return 2; }
+from_b :: () -> s64 { return greet(); }

examples/0723-modules-flat-vs-namespaced.sx

@@ -0,0 +1,17 @@
+// fix-0102c (issue 0102): one FLAT and one NAMESPACED author of `value`. The
+// bare call `value()` binds the FLAT author (10); the namespaced author is
+// reached only through `nm.value()` (20). A namespaced author must NOT make the
+// bare call ambiguous — only flat authors collide.
+#import "modules/std.sx";
+#import "0723-modules-flat-vs-namespaced/flat.sx";
+nm :: #import "0723-modules-flat-vs-namespaced/named.sx";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("bare binds flat", value() == 10);
+    report("nm.value binds named", nm.value() == 20);
+    0
+}

examples/0723-modules-flat-vs-namespaced/flat.sx

@@ -0,0 +1,3 @@
+// Flat-imported author of `value`. A bare `value()` in the consumer binds THIS
+// one — the only bare (flat) author of the name.
+value :: () -> s64 { return 10; }

examples/0723-modules-flat-vs-namespaced/named.sx

@@ -0,0 +1,4 @@
+// Namespaced-imported author of `value`. Reachable only as `nm.value`; it never
+// enters the flat merge, so it neither shadows the flat author nor makes the
+// bare call ambiguous.
+value :: () -> s64 { return 20; }

examples/0724-modules-flat-same-name-ambiguous.sx

@@ -0,0 +1,12 @@
+// fix-0102c (issue 0102): a genuinely-ambiguous bare call. `main` flat-imports
+// two modules that each author `dup` and neither is `main`'s own — a bare
+// `dup()` can't pick one, so the compiler rejects it with a loud diagnostic
+// instead of silently first-wins-binding one. Qualify the call to disambiguate.
+#import "modules/std.sx";
+#import "0724-modules-flat-same-name-ambiguous/a.sx";
+#import "0724-modules-flat-same-name-ambiguous/b.sx";
+
+main :: () -> s32 {
+    print("{}\n", dup());
+    0
+}

examples/0724-modules-flat-same-name-ambiguous/a.sx

@@ -0,0 +1,3 @@
+// One of two flat authors of `dup`. A consumer that flat-imports BOTH and calls
+// `dup` bare cannot pick between them.
+dup :: () -> s64 { return 1; }

examples/0724-modules-flat-same-name-ambiguous/b.sx

@@ -0,0 +1,2 @@
+// The second flat author of `dup`.
+dup :: () -> s64 { return 2; }

examples/0725-modules-flat-dir-same-name.sx

@@ -0,0 +1,17 @@
+// fix-0102c (issue 0102): two flat DIRECTORY imports each author a same-name
+// `tag`. A directory flat-import exposes the directory's authored functions, so
+// `caller1`/`caller2` are visible here, and each binds its OWN directory's `tag`
+// when it calls bare — per-source binding across directory imports (100 / 200).
+#import "modules/std.sx";
+#import "0725-modules-flat-dir-same-name/d1";
+#import "0725-modules-flat-dir-same-name/d2";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("caller1 binds d1.tag", caller1() == 100);
+    report("caller2 binds d2.tag", caller2() == 200);
+    0
+}

examples/0725-modules-flat-dir-same-name/d1/one.sx

@@ -0,0 +1,3 @@
+// d1's author of `tag`. `caller1` (also in d1) binds d1's own `tag` (100).
+tag     :: () -> s64 { return 100; }
+caller1 :: () -> s64 { return tag(); }

examples/0725-modules-flat-dir-same-name/d2/two.sx

@@ -0,0 +1,4 @@
+// d2's author of `tag`. `caller2` (also in d2) binds d2's own `tag` (200),
+// even though d1's `tag` is the first-wins merge winner.
+tag     :: () -> s64 { return 200; }
+caller2 :: () -> s64 { return tag(); }

examples/0726-modules-flat-same-name-variadic.sx

@@ -0,0 +1,23 @@
+// fix-0102c F1 (issue 0102): two flat FILE imports each author same-name free
+// functions whose VARIADIC SHAPE differs. `combine` is fixed-arity in a.sx
+// (the first-wins winner) but variadic in b.sx (the shadow); `pick` is the
+// reverse. Each module's bare call must pack arguments against ITS OWN
+// author's signature — not the first-wins author's. Pre-fix the call path
+// re-fetched the first-wins AST by name to drive variadic packing, so b.sx's
+// variadic `combine` was packed as if fixed (and its fixed `pick` as if
+// variadic) → wrong lowering. Regression for the F1 review finding.
+#import "modules/std.sx";
+#import "0726-modules-flat-same-name-variadic/a.sx";
+#import "0726-modules-flat-same-name-variadic/b.sx";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("from_a combine fixed", from_a_combine() == 30);
+    report("from_b combine variadic", from_b_combine() == 10);
+    report("from_a pick variadic", from_a_pick() == 6);
+    report("from_b pick fixed", from_b_pick() == 5);
+    0
+}

examples/0726-modules-flat-same-name-variadic/a.sx

@@ -0,0 +1,11 @@
+// a.sx is the first-wins winner for both names. `combine` is FIXED arity;
+// `pick` is VARIADIC. `from_a_*` call them bare — a authors the winner, so
+// they resolve through the existing path and pack against a's own shapes.
+combine :: (x: s64, y: s64) -> s64 { return x + y; }
+pick :: (..xs: []s64) -> s64 {
+    result := 0;
+    for xs: (it) { result = result + it; }
+    result
+}
+from_a_combine :: () -> s64 { return combine(10, 20); }
+from_a_pick :: () -> s64 { return pick(1, 2, 3); }

examples/0726-modules-flat-same-name-variadic/b.sx

@@ -0,0 +1,12 @@
+// b.sx is the SHADOW author for both names, with the OPPOSITE shapes:
+// `combine` is VARIADIC, `pick` is FIXED. Each `from_b_*` bare call must pack
+// against b's OWN author's signature (the F1 fix) — combine sums its variadic
+// pack, pick subtracts its two fixed args.
+combine :: (..xs: []s64) -> s64 {
+    result := 0;
+    for xs: (it) { result = result + it; }
+    result
+}
+pick :: (a: s64, b: s64) -> s64 { return b - a; }
+from_b_combine :: () -> s64 { return combine(1, 2, 3, 4); }
+from_b_pick :: () -> s64 { return pick(2, 7); }

examples/0727-modules-user-ns-m0.sx

@@ -0,0 +1,20 @@
+// fix-0102c (issue 0102): a user namespace alias literally named `__m0`
+// coexists with flat same-name imports. fix-0102 resolves same-name authors by
+// FnDecl IDENTITY — there are no synthetic `__m0`-style names to collide with —
+// so a user namespace spelled `__m0` is just an ordinary namespace: `call_a`
+// binds a.ping (1), `call_b` binds b.ping (2), and `__m0.ping` reaches m.ping (99).
+#import "modules/std.sx";
+#import "0727-modules-user-ns-m0/a.sx";
+#import "0727-modules-user-ns-m0/b.sx";
+__m0 :: #import "0727-modules-user-ns-m0/m.sx";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("call_a binds a.ping", call_a() == 1);
+    report("call_b binds b.ping", call_b() == 2);
+    report("__m0.ping binds m.ping", __m0.ping() == 99);
+    0
+}

examples/0727-modules-user-ns-m0/a.sx

@@ -0,0 +1,3 @@
+// Flat author of `ping`; `call_a` binds a.sx's own `ping` (1).
+ping   :: () -> s64 { return 1; }
+call_a :: () -> s64 { return ping(); }

examples/0727-modules-user-ns-m0/b.sx

@@ -0,0 +1,3 @@
+// Second flat author of `ping`; `call_b` binds b.sx's own `ping` (2).
+ping   :: () -> s64 { return 2; }
+call_b :: () -> s64 { return ping(); }

examples/0727-modules-user-ns-m0/m.sx

@@ -0,0 +1,3 @@
+// Imported under a user namespace literally named `__m0`. Reached as
+// `__m0.ping` (99); coexists with the flat `ping` collision.
+ping :: () -> s64 { return 99; }

examples/0728-modules-flat-same-name-paramtype.sx

@@ -0,0 +1,22 @@
+// fix-0102c F2 (issue 0102): two flat FILE imports each author a same-name free
+// function `apply` with a DIFFERENT parameter TYPE — a.sx takes a value
+// (`x: s64`), b.sx takes a pointer (`x: *s64`). The first-wins import merge
+// keeps a.sx's value-typed `apply`, but each module's bare call must type its
+// arguments against ITS OWN author. b.sx's `from_b` passes a local `v` to its
+// pointer-param `apply` via implicit address-of; before the fix the arg was
+// typed against the first-wins (value) winner, lowered as a value, then the
+// resolved pointer-param author was called with that value bit-cast to a
+// pointer — a segfault. Regression: per-source parameter target typing.
+#import "modules/std.sx";
+#import "0728-modules-flat-same-name-paramtype/a.sx";
+#import "0728-modules-flat-same-name-paramtype/b.sx";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("from_a binds a.apply (value param)", from_a() == 11);
+    report("from_b binds b.apply (pointer param)", from_b() == 42);
+    0
+}

examples/0728-modules-flat-same-name-paramtype/a.sx

@@ -0,0 +1,5 @@
+// a.sx authors `apply` taking a VALUE. It is imported first, so it is the
+// first-wins merge winner. `from_a` calls `apply` bare on a value local — its
+// own author wins (own == winner → existing path, byte-for-byte unchanged).
+apply  :: (x: s64) -> s64 { return x + 1; }
+from_a :: () -> s64 { v : s64 = 10; return apply(v); }

examples/0728-modules-flat-same-name-paramtype/b.sx

@@ -0,0 +1,7 @@
+// b.sx authors its OWN `apply` taking a POINTER. `from_b` passes a value local
+// `v` bare; the pointer param must drive implicit address-of so the callee
+// mutates `v` in place (×2 → 42). Before the fix, `v` was typed against a.sx's
+// value-param winner, lowered as a value, then the resolved pointer-param
+// author was called with that value forced to a pointer (segfault).
+apply  :: (x: *s64) { x.* = x.* * 2; }
+from_b :: () -> s64 { v : s64 = 21; apply(v); return v; }

examples/0729-modules-flat-same-name-foreign.sx

@@ -0,0 +1,14 @@
+// fix-0102c (issue 0102) F3 regression: two flat FILE imports each `#foreign`
+// the SAME libc symbol under the SAME sx name `absval`. The bare-call resolver
+// must NOT count `#foreign` (non-plain) authors when deciding ambiguity — it
+// filters them out, returns "no rerouting", and the existing first-wins foreign
+// dispatch binds the call. A same-name foreign collision therefore compiles and
+// runs (master behavior), it does NOT error as ambiguous.
+#import "modules/std.sx";
+#import "0729-modules-flat-same-name-foreign/a.sx";
+#import "0729-modules-flat-same-name-foreign/b.sx";
+
+main :: () -> s32 {
+    print("absval = {}\n", absval(-7));
+    0
+}

examples/0729-modules-flat-same-name-foreign/a.sx

@@ -0,0 +1,5 @@
+// One of two flat authors of `absval`, a `#foreign` libc binding. A consumer
+// flat-importing BOTH must NOT see this as an ambiguous bare-call collision —
+// foreign authors are never rerouted by the bare-call resolver, so the call
+// falls to the existing first-wins foreign dispatch.
+absval :: (n: s32) -> s32 #foreign libc "abs";

examples/0729-modules-flat-same-name-foreign/b.sx

@@ -0,0 +1,2 @@
+// The second flat author of `absval` — the identical `#foreign` libc binding.
+absval :: (n: s32) -> s32 #foreign libc "abs";

examples/0730-modules-flat-same-name-default-arg.sx

@@ -0,0 +1,20 @@
+// fix-0102d site 1 (issue 0102): two flat FILE imports each author a same-name
+// free function `cfg` with a DIFFERENT default value for its trailing param —
+// a.sx defaults to 10, b.sx to 20. Each module calls `cfg()` bare with the arg
+// OMITTED. The omitted trailing arg must be filled from the RESOLVED author's
+// default (own-author wins), not the first-wins winner's. Before the fix,
+// `from_b`'s `cfg()` expanded to the winner a.sx's default (10) and returned 10.
+// Regression: per-source default-argument expansion.
+#import "modules/std.sx";
+#import "0730-modules-flat-same-name-default-arg/a.sx";
+#import "0730-modules-flat-same-name-default-arg/b.sx";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("from_a binds a.cfg default (10)", from_a() == 10);
+    report("from_b binds b.cfg default (20)", from_b() == 20);
+    0
+}

examples/0730-modules-flat-same-name-default-arg/a.sx

@@ -0,0 +1,5 @@
+// a.sx authors `cfg` defaulting to 10. Imported first, so it is the first-wins
+// merge winner. `from_a` calls `cfg()` with the arg omitted — own == winner →
+// existing default-expansion path, byte-for-byte unchanged.
+cfg    :: (n: s64 = 10) -> s64 { return n; }
+from_a :: () -> s64 { return cfg(); }

examples/0730-modules-flat-same-name-default-arg/b.sx

@@ -0,0 +1,5 @@
+// b.sx authors its OWN `cfg` defaulting to 20. `from_b`'s `cfg()` omits the
+// arg; the omitted trailing default must come from b.sx's author (20), not the
+// first-wins winner from a.sx (10).
+cfg    :: (n: s64 = 20) -> s64 { return n; }
+from_b :: () -> s64 { return cfg(); }

examples/0731-modules-flat-same-name-closure.sx

@@ -0,0 +1,22 @@
+// fix-0102d site 2 (issue 0102): two flat FILE imports each author a same-name
+// free function `pick` (a.sx returns 1, b.sx returns 2). Each module takes
+// `pick` as a function VALUE — both as `closure(pick)` and as a bare-name
+// fn-pointer binding (`g : () -> s64 = pick`). The captured FuncId must be the
+// RESOLVED author's (own-author wins), not the first-wins winner's. Before the
+// fix, b.sx's `closure(pick)` / `pick`-as-value both captured a.sx's winner
+// (1). Regression: per-source function-value conversion (closure + func_ref).
+#import "modules/std.sx";
+#import "0731-modules-flat-same-name-closure/a.sx";
+#import "0731-modules-flat-same-name-closure/b.sx";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("from_a closure binds a.pick (1)", from_a_closure() == 1);
+    report("from_b closure binds b.pick (2)", from_b_closure() == 2);
+    report("from_a fn-value binds a.pick (1)", from_a_value() == 1);
+    report("from_b fn-value binds b.pick (2)", from_b_value() == 2);
+    0
+}

examples/0731-modules-flat-same-name-closure/a.sx

@@ -0,0 +1,6 @@
+// a.sx authors `pick` returning 1. Imported first → first-wins winner.
+// `from_a_closure` / `from_a_value` take a.sx's own author (own == winner →
+// existing path, byte-for-byte unchanged).
+pick :: () -> s64 { return 1; }
+from_a_closure :: () -> s64 { f := closure(pick); return f(); }
+from_a_value   :: () -> s64 { g : () -> s64 = pick; return g(); }

examples/0731-modules-flat-same-name-closure/b.sx

@@ -0,0 +1,6 @@
+// b.sx authors its OWN `pick` returning 2. Taking `pick` as a value —
+// `closure(pick)` or `g : () -> s64 = pick` — must capture b.sx's author (2),
+// not the first-wins winner from a.sx (1).
+pick :: () -> s64 { return 2; }
+from_b_closure :: () -> s64 { f := closure(pick); return f(); }
+from_b_value   :: () -> s64 { g : () -> s64 = pick; return g(); }

examples/0732-modules-flat-same-name-ufcs.sx

@@ -0,0 +1,19 @@
+// fix-0102d site 3 (issue 0102): two flat FILE imports each author a same-name
+// free function `bump` (a.sx adds 1, b.sx adds 100). Each module dispatches it
+// via free-function UFCS — `v.bump()` lowers to `bump(v)`. The dispatched
+// author must be the RESOLVED one for the receiver's source (own-author wins),
+// not the first-wins winner. Before the fix, b.sx's `v.bump()` dispatched
+// a.sx's winner (+1 → 11). Regression: per-source free-function UFCS dispatch.
+#import "modules/std.sx";
+#import "0732-modules-flat-same-name-ufcs/a.sx";
+#import "0732-modules-flat-same-name-ufcs/b.sx";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("from_a v.bump() binds a.bump (+1)", from_a_ufcs() == 11);
+    report("from_b v.bump() binds b.bump (+100)", from_b_ufcs() == 110);
+    0
+}

examples/0732-modules-flat-same-name-ufcs/a.sx

@@ -0,0 +1,5 @@
+// a.sx authors `bump` adding 1. Imported first → first-wins winner. `from_a`'s
+// `v.bump()` resolves a.sx's own author (own == winner → existing UFCS path,
+// byte-for-byte unchanged).
+bump   :: (x: s64) -> s64 { return x + 1; }
+from_a_ufcs :: () -> s64 { v : s64 = 10; return v.bump(); }

examples/0732-modules-flat-same-name-ufcs/b.sx

@@ -0,0 +1,4 @@
+// b.sx authors its OWN `bump` adding 100. `from_b`'s `v.bump()` must dispatch
+// b.sx's author (+100 → 110), not the first-wins winner from a.sx (+1).
+bump   :: (x: s64) -> s64 { return x + 100; }
+from_b_ufcs :: () -> s64 { v : s64 = 10; return v.bump(); }

examples/0733-modules-flat-same-name-comptime-run.sx

@@ -0,0 +1,21 @@
+// fix-0102d site 4 (issue 0102): two flat FILE imports each author a same-name
+// free function `compute` (a.sx returns 7, b.sx returns 70) and each evaluates
+// it at comptime via `NAME :: #run compute();`. The #run body must resolve the
+// bare callee from ITS OWN module's source context (own-author wins), so a.sx's
+// const is 7 and b.sx's is 70. Before the fix, the #run body lowered with the
+// main file's source perspective, where `compute` is authored by two flat
+// imports and neither is main's own — so it was reported AMBIGUOUS and the
+// build failed. Regression: per-source comptime #run callee resolution.
+#import "modules/std.sx";
+#import "0733-modules-flat-same-name-comptime-run/a.sx";
+#import "0733-modules-flat-same-name-comptime-run/b.sx";
+
+report :: (label: string, ok: bool) {
+    if ok { print("{}: ok\n", label); } else { print("{}: FAIL\n", label); }
+}
+
+main :: () -> s32 {
+    report("a.sx #run binds a.compute (7)", get_a() == 7);
+    report("b.sx #run binds b.compute (70)", get_b() == 70);
+    0
+}

examples/0733-modules-flat-same-name-comptime-run/a.sx

@@ -0,0 +1,6 @@
+// a.sx authors `compute` returning 7 and evaluates it at comptime. Imported
+// first → first-wins winner; own == winner, but the #run must still lower in
+// a.sx's source context so the bare `compute` resolves at all (not ambiguous).
+compute :: () -> s64 { return 7; }
+A_VAL :: #run compute();
+get_a :: () -> s64 { return A_VAL; }

examples/0733-modules-flat-same-name-comptime-run/b.sx

@@ -0,0 +1,6 @@
+// b.sx authors its OWN `compute` returning 70. Its `#run compute()` must bind
+// b.sx's author (70) — own-author wins in b.sx's source context — not the
+// first-wins winner from a.sx (7).
+compute :: () -> s64 { return 70; }
+B_VAL :: #run compute();
+get_b :: () -> s64 { return B_VAL; }

examples/0734-modules-flat-same-name-ufcs-ambiguous.sx

@@ -0,0 +1,16 @@
+// fix-0102d site 3 ambiguity (issue 0102): two flat FILE imports each author a
+// same-name free function `dup`, and the MAIN file (which authors neither)
+// dispatches it via free-function UFCS `v.dup()`. With two distinct flat
+// authors reachable and no own-author to prefer, the call is ambiguous — the
+// UFCS dispatch site must emit the loud "qualify the call" diagnostic rather
+// than silently binding the first-wins winner. Mirrors 0724 (the bare-call
+// ambiguity) one site over.
+#import "modules/std.sx";
+#import "0734-modules-flat-same-name-ufcs-ambiguous/a.sx";
+#import "0734-modules-flat-same-name-ufcs-ambiguous/b.sx";
+
+main :: () -> s32 {
+    v : s64 = 10;
+    print("{}\n", v.dup());
+    0
+}

examples/0734-modules-flat-same-name-ufcs-ambiguous/a.sx

@@ -0,0 +1,2 @@
+// a.sx authors `dup` (+1). One of two distinct flat authors of `dup`.
+dup :: (x: s64) -> s64 { return x + 1; }

examples/0734-modules-flat-same-name-ufcs-ambiguous/b.sx

@@ -0,0 +1,3 @@
+// b.sx authors its OWN `dup` (+2) — the second distinct flat author. Main
+// imports both and authors neither, so `v.dup()` from main is ambiguous.
+dup :: (x: s64) -> s64 { return x + 2; }

examples/0735-modules-flat-same-name-fn-value-winner.sx

@@ -0,0 +1,17 @@
+// fix-0102d site 2 / attempt-2 (issue 0102): the first-wins winner's body is
+// independently BROKEN (references an undefined symbol) and is never used. A
+// shadow author from a later flat import takes its OWN `pick` as a function
+// VALUE (`g : () -> s64 = pick`). The value must bind the shadow (own-author
+// wins) and the broken winner must NOT be lowered — a rerouted fn value never
+// uses the winner. Before the fix the fn-value site eagerly lazily-lowered the
+// name-keyed winner BEFORE the resolver rerouted, surfacing the winner's
+// `unresolved 'missing_from_a'` for a function the value never touches.
+// Regression: per-source function-value conversion must not pre-lower the winner.
+#import "modules/std.sx";
+#import "0735-modules-flat-same-name-fn-value-winner/a.sx";
+#import "0735-modules-flat-same-name-fn-value-winner/b.sx";
+
+main :: () -> s32 {
+    print("from_b_value = {}\n", from_b_value());
+    0
+}

examples/0735-modules-flat-same-name-fn-value-winner/a.sx

@@ -0,0 +1,4 @@
+// a.sx authors `pick` (imported first → the first-wins name-keyed winner) but
+// its body references an undefined symbol, so lowering a.pick AT ALL is an
+// error. Nothing uses a.pick — taking b.pick as a value must not pre-lower it.
+pick :: () -> s64 { return missing_from_a(); }

examples/0735-modules-flat-same-name-fn-value-winner/b.sx

@@ -0,0 +1,7 @@
+// b.sx authors its OWN `pick` (returns 2) and takes it as a function VALUE. The
+// value binds b.pick (own-author wins), never the broken winner from a.sx.
+pick :: () -> s64 { return 2; }
+from_b_value :: () -> s64 {
+    g : () -> s64 = pick;
+    return g();
+}

examples/expected/0722-modules-flat-same-name-own.exit

@@ -0,0 +1 @@
+0

examples/expected/0722-modules-flat-same-name-own.stderr

@@ -0,0 +1 @@
+

examples/expected/0722-modules-flat-same-name-own.stdout

@@ -0,0 +1,2 @@
+from_a binds a.greet: ok
+from_b binds b.greet: ok

examples/expected/0723-modules-flat-vs-namespaced.exit

@@ -0,0 +1 @@
+0

examples/expected/0723-modules-flat-vs-namespaced.stderr

@@ -0,0 +1 @@
+

examples/expected/0723-modules-flat-vs-namespaced.stdout

@@ -0,0 +1,2 @@
+bare binds flat: ok
+nm.value binds named: ok

examples/expected/0724-modules-flat-same-name-ambiguous.exit

@@ -0,0 +1 @@
+1

examples/expected/0724-modules-flat-same-name-ambiguous.stderr

@@ -0,0 +1,5 @@
+error: 'dup' is ambiguous; declared by multiple imported modules — qualify the call
+  --> examples/0724-modules-flat-same-name-ambiguous.sx:10:19
+   |
+10 |     print("{}\n", dup());
+   |                   ^^^

examples/expected/0724-modules-flat-same-name-ambiguous.stdout

@@ -0,0 +1 @@
+

examples/expected/0725-modules-flat-dir-same-name.exit

@@ -0,0 +1 @@
+0

examples/expected/0725-modules-flat-dir-same-name.stderr

@@ -0,0 +1 @@
+

examples/expected/0725-modules-flat-dir-same-name.stdout

@@ -0,0 +1,2 @@
+caller1 binds d1.tag: ok
+caller2 binds d2.tag: ok

examples/expected/0726-modules-flat-same-name-variadic.exit

@@ -0,0 +1 @@
+0

examples/expected/0726-modules-flat-same-name-variadic.stderr

@@ -0,0 +1 @@
+

examples/expected/0726-modules-flat-same-name-variadic.stdout

@@ -0,0 +1,4 @@
+from_a combine fixed: ok
+from_b combine variadic: ok
+from_a pick variadic: ok
+from_b pick fixed: ok

examples/expected/0727-modules-user-ns-m0.exit

@@ -0,0 +1 @@
+0

examples/expected/0727-modules-user-ns-m0.stderr

@@ -0,0 +1 @@
+

examples/expected/0727-modules-user-ns-m0.stdout

@@ -0,0 +1,3 @@
+call_a binds a.ping: ok
+call_b binds b.ping: ok
+__m0.ping binds m.ping: ok

examples/expected/0728-modules-flat-same-name-paramtype.exit

@@ -0,0 +1 @@
+0

examples/expected/0728-modules-flat-same-name-paramtype.stderr

@@ -0,0 +1 @@
+

examples/expected/0728-modules-flat-same-name-paramtype.stdout

@@ -0,0 +1,2 @@
+from_a binds a.apply (value param): ok
+from_b binds b.apply (pointer param): ok

examples/expected/0729-modules-flat-same-name-foreign.exit

@@ -0,0 +1 @@
+0

examples/expected/0729-modules-flat-same-name-foreign.stderr

@@ -0,0 +1 @@
+

examples/expected/0729-modules-flat-same-name-foreign.stdout

@@ -0,0 +1 @@
+absval = 7

examples/expected/0730-modules-flat-same-name-default-arg.exit

@@ -0,0 +1 @@
+0

examples/expected/0730-modules-flat-same-name-default-arg.stderr

@@ -0,0 +1 @@
+

examples/expected/0730-modules-flat-same-name-default-arg.stdout

@@ -0,0 +1,2 @@
+from_a binds a.cfg default (10): ok
+from_b binds b.cfg default (20): ok

examples/expected/0731-modules-flat-same-name-closure.exit

@@ -0,0 +1 @@
+0

examples/expected/0731-modules-flat-same-name-closure.stderr

@@ -0,0 +1 @@
+

examples/expected/0731-modules-flat-same-name-closure.stdout

@@ -0,0 +1,4 @@
+from_a closure binds a.pick (1): ok
+from_b closure binds b.pick (2): ok
+from_a fn-value binds a.pick (1): ok
+from_b fn-value binds b.pick (2): ok

examples/expected/0732-modules-flat-same-name-ufcs.exit

@@ -0,0 +1 @@
+0

examples/expected/0732-modules-flat-same-name-ufcs.stderr

@@ -0,0 +1 @@
+

examples/expected/0732-modules-flat-same-name-ufcs.stdout

@@ -0,0 +1,2 @@
+from_a v.bump() binds a.bump (+1): ok
+from_b v.bump() binds b.bump (+100): ok

examples/expected/0733-modules-flat-same-name-comptime-run.exit

@@ -0,0 +1 @@
+0

examples/expected/0733-modules-flat-same-name-comptime-run.stderr

@@ -0,0 +1 @@
+

examples/expected/0733-modules-flat-same-name-comptime-run.stdout

@@ -0,0 +1,2 @@
+a.sx #run binds a.compute (7): ok
+b.sx #run binds b.compute (70): ok

examples/expected/0734-modules-flat-same-name-ufcs-ambiguous.exit

@@ -0,0 +1 @@
+1

examples/expected/0734-modules-flat-same-name-ufcs-ambiguous.stderr

@@ -0,0 +1,5 @@
+error: 'dup' is ambiguous; declared by multiple imported modules — qualify the call
+  --> examples/0734-modules-flat-same-name-ufcs-ambiguous.sx:14:19
+   |
+14 |     print("{}\n", v.dup());
+   |                   ^^^^^

examples/expected/0734-modules-flat-same-name-ufcs-ambiguous.stdout

@@ -0,0 +1 @@
+

examples/expected/0735-modules-flat-same-name-fn-value-winner.exit

@@ -0,0 +1 @@
+0

examples/expected/0735-modules-flat-same-name-fn-value-winner.stderr

@@ -0,0 +1 @@
+

examples/expected/0735-modules-flat-same-name-fn-value-winner.stdout

@@ -0,0 +1 @@
+from_b_value = 2

issues/0102-flat-import-same-signature-collision.md

@@ -0,0 +1,102 @@
+# 0102 — flat-import same-name function collision (per-source binding)
+
+**RESOLVED.** Two **flat** imports (bare `#import "a.sx"` / a flat directory
+import, NOT a namespaced `ns :: #import`) that each author a top-level free
+function with the **same short name** collided in IR lowering. The flat/
+directory merge keeps exactly **one** author per name in the merged decl list
+(first-wins), and every bare-name consumer site — call dispatch, default-arg
+expansion, function-value capture, free-function UFCS, comptime `#run` — read
+that one **name-keyed** winner. So when module `b.sx` authored its own `greet`
+but `a.sx` was imported first, `b.sx`'s own bare `greet()` silently bound
+`a.sx`'s author. Unlike issue 0100 (which crashed on a param-count assert when
+the AST/FuncId split across modules), this miscompiled **silently**: the wrong
+same-name author ran, with no diagnostic.
+
+The defect had two faces, both rooted in name-keyed identity across a flat
+collision:
+
+1. **Lowering** keyed function bodies by short name (`fn_ast_map` /
+   `resolveFuncByName` are first-wins), so a shadowed author never got its own
+   FuncId or body — there was nothing to bind even if a consumer wanted the
+   per-source author.
+2. **Resolution** at every bare-name consumer site re-looked-up the winner by
+   name, so even once shadow authors had distinct FuncIds, the consumer sites
+   kept binding the first-wins winner.
+
+## Fix — four sub-steps (`src/imports.zig`, `src/ir/lower.zig`)
+
+- **0102a — retain dup authors + identity indexes.** The flat/directory merge
+  keeps first-wins in the merged scope (unchanged), but now *also* retains
+  every dropped same-name author in `program_index.module_fns`
+  (`path → name → *FnDecl`) plus a `flat_import_graph` (`file → flat-import
+  edges`). Resolution is untouched at this step — the indexes just make the
+  shadowed authors addressable.
+
+- **0102b — identity-addressable function lowering.** `fn_decl_fids`
+  (`*const ast.FnDecl → FuncId`) lets a body be declared + lowered against a
+  **specific** `*FnDecl` (`lowerFunctionBodyInto` / `bareAuthorFuncId`) instead
+  of a name. A shadow author gets a fresh same-name FuncId in its own module's
+  visibility context; the winner keeps the name-keyed slot. `scanDecls` keys
+  `fn_decl_fids` by the stable `module_fns` `*FnDecl`.
+
+- **0102c — THE resolver + call path + param typing.**
+  `resolveBareCallee(name, caller_file) -> .func(ResolvedAuthor) | .ambiguous |
+  .none` (`src/ir/lower.zig`). It returns `.none` whenever the outcome would
+  equal first-wins (single author, or own-author == winner), so every
+  single-author / local / parameter / std / qualified / foreign / generic /
+  builtin name resolves byte-for-byte as before. Only a genuine flat collision
+  reroutes: own-author wins; else the caller's flat-reachable authors — `≥2`
+  distinct → `.ambiguous` (loud "qualify the call" diagnostic), exactly one
+  differing from the winner → bind it. Routed the **primary call path** and the
+  call's **parameter target typing** (so a `*T`-param shadow gets implicit
+  address-of, not a value bit-cast to a pointer → segfault).
+
+- **0102d — the four remaining bare-name sites.** Routed the SAME resolver
+  through every other site that resolved a bare callee/function-name by
+  first-wins, each gated exactly as the call path (plain top-level identifier,
+  no scope-mangle / UFCS alias / local shadow; act on `.func` / `.ambiguous`,
+  fall through on `.none`):
+  1. **Default-argument expansion** (`expandCallDefaults`): omitted trailing
+     args fill from the RESOLVED author's defaults, not the winner's.
+  2. **Function-value conversion** (`closure(fn)` and the bare-fn-as-value
+     `func_ref` / fn-ptr / closure-coercion path): captures the resolved
+     author's FuncId. The winner's body is lazily lowered ONLY on the `.none`
+     fallback — a rerouted value never uses the winner, so taking a shadow as a
+     value must not pre-lower (and possibly mis-diagnose) the winner's body.
+  3. **Free-function UFCS** (`recv.fn()` → `fn(recv, …)`): dispatches the
+     resolved author for the receiver's source.
+  4. **Comptime `#run`** of a bare call: `lowerMainAndComptime` now sets
+     `current_source_file` per decl, so a `NAME :: #run f()` in an imported
+     module resolves `f` from THAT module's flat imports (own-author wins)
+     rather than the main file's perspective (where two flat authors made it
+     spuriously `.ambiguous` and failed the build).
+
+## Regression tests
+
+`examples/0722`–`0735` (each a focused multi-file flat-collision scene that
+fails on pre-fix code and passes after):
+
+- `0722-modules-flat-same-name-own` — own-author wins on the call path.
+- `0723-modules-flat-vs-namespaced` — a flat author + a namespaced same-name
+  author don't collide.
+- `0724-modules-flat-same-name-ambiguous` — `≥2` flat authors, bare call →
+  loud diagnostic.
+- `0725-modules-flat-dir-same-name` — flat **directory** import collision.
+- `0726-modules-flat-same-name-variadic` — per-source variadic packing.
+- `0728-modules-flat-same-name-paramtype` — per-source parameter target typing
+  (value vs pointer param).
+- `0729-modules-flat-same-name-foreign` — same-name `#foreign` authors are NOT
+  rerouted (non-plain authors keep first-wins).
+- `0730-modules-flat-same-name-default-arg` — per-source default-arg expansion.
+- `0731-modules-flat-same-name-closure` — per-source `closure(fn)` + bare
+  fn-value capture.
+- `0732-modules-flat-same-name-ufcs` — per-source free-function UFCS dispatch.
+- `0733-modules-flat-same-name-comptime-run` — per-source comptime `#run`
+  callee.
+- `0734-modules-flat-same-name-ufcs-ambiguous` — `≥2` flat authors, UFCS call
+  → loud diagnostic (pre-fix: silently bound the winner).
+- `0735-modules-flat-same-name-fn-value-winner` — the first-wins winner's body
+  is independently broken and never used; a shadow taken as a function value
+  binds the shadow and runs while the winner is NOT lowered (pre-fix: the
+  fn-value site eagerly lowered the winner before the resolver rerouted,
+  surfacing the winner's error for a function the value never touches).

readme.md

@@ -393,6 +393,12 @@ Direct C header import:
 math :: #import "modules/math.sx";     // namespaced import
 ```
 
+When two flat-imported modules each define a function of the same name, every
+module's own code binds its OWN author — a bare call resolves to the same-name
+function in the caller's module (or in its single flat import that provides it).
+A bare call to a name that two or more flat imports both provide is ambiguous and
+is rejected; qualify it with a namespaced import (`m :: #import …; m.fn()`).
+
 ### Implicit Context
 
 Every program gets an implicit `context` with a default allocator:

src/core.zig

@@ -26,6 +26,12 @@ pub const Compilation = struct {
     import_sources: std.StringHashMap([:0]const u8),
     module_scopes: std.StringHashMap(std.StringHashMap(void)),
     import_graph: std.StringHashMap(std.StringHashMap(void)),
+    /// Flat-only subset of `import_graph` (bare `#import` edges, no namespaced
+    /// `ns :: #import`). Borrowed by `ProgramIndex.flat_import_graph`.
+    flat_import_graph: std.StringHashMap(std.StringHashMap(void)),
+    /// Per-module authored-function index (`path → name → *const FnDecl`).
+    /// Borrowed by `ProgramIndex.module_fns`.
+    module_fns: imports.ModuleFns,
     ir_emitter: ?ir.LLVMEmitter = null,
     /// Lowered IR module, kept alive past `generateCode` so post-link
     /// callbacks can re-enter the interpreter to invoke sx functions
@@ -52,6 +58,8 @@ pub const Compilation = struct {
             .import_sources = std.StringHashMap([:0]const u8).init(allocator),
             .module_scopes = std.StringHashMap(std.StringHashMap(void)).init(allocator),
             .import_graph = std.StringHashMap(std.StringHashMap(void)).init(allocator),
+            .flat_import_graph = std.StringHashMap(std.StringHashMap(void)).init(allocator),
+            .module_fns = imports.ModuleFns.init(allocator),
             .target_config = target_config,
             .stdlib_paths = stdlib_paths,
         };
@@ -101,6 +109,7 @@ pub const Compilation = struct {
             &self.diagnostics,
             self.stdlib_paths,
             &self.import_graph,
+            &self.flat_import_graph,
             self.comptimeContext(),
         ) catch return error.CompileError;
 
@@ -111,6 +120,11 @@ pub const Compilation = struct {
             self.module_scopes.put(entry.key_ptr.*, entry.value_ptr.scope) catch {};
         }
 
+        // Per-module authored-function index, built from the SAME modules as
+        // `module_scopes` (main + every cache entry). Keyed by path; same-name
+        // cross-module authors stay distinct under their own paths.
+        imports.buildModuleFns(self.allocator, self.file_path, mod, &cache, &self.module_fns) catch {};
+
         // Store main file source in import_sources so error reporting can find it
         self.import_sources.put(self.file_path, self.source) catch {};
 
@@ -276,6 +290,8 @@ pub const Compilation = struct {
         lowering.diagnostics = &self.diagnostics;
         lowering.program_index.module_scopes = &self.module_scopes;
         lowering.program_index.import_graph = &self.import_graph;
+        lowering.program_index.flat_import_graph = &self.flat_import_graph;
+        lowering.program_index.module_fns = &self.module_fns;
         lowering.lowerRoot(root);
         if (self.diagnostics.hasErrors()) return error.CompileError;
 

src/imports.test.zig

@@ -0,0 +1,188 @@
+// Tests for imports.zig — flat-import name-resolution data retention (fix-0102a).
+
+const std = @import("std");
+const ast = @import("ast.zig");
+const parser = @import("parser.zig");
+const imports = @import("imports.zig");
+
+var g_test_threaded: ?std.Io.Threaded = null;
+fn testIo() std.Io {
+    if (g_test_threaded == null) {
+        g_test_threaded = std.Io.Threaded.init(std.heap.page_allocator, .{});
+    }
+    return g_test_threaded.?.io();
+}
+
+// Two flat-imported modules each author `greet`; a third is namespaced. The
+// step retains BOTH `greet` authors under their own paths in `module_fns` and
+// records the namespaced import in `import_graph` but NOT in `flat_import_graph`
+// — WITHOUT touching the merged scope: `mod.decls` stays byte-for-byte
+// first-wins (one `greet`, a.sx's), exactly as on `wt-fix-0102-base`.
+test "imports: module_fns retains same-name cross-module fns; flat_import_graph excludes namespaced edge" {
+    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
+    defer arena.deinit();
+    const alloc = arena.allocator();
+    const io = testIo();
+
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+
+    try tmp.dir.writeFile(io, .{ .sub_path = "a.sx", .data = "greet :: () -> s64 { 1 }\n" });
+    try tmp.dir.writeFile(io, .{ .sub_path = "b.sx", .data = "greet :: () -> s64 { 2 }\n" });
+    try tmp.dir.writeFile(io, .{ .sub_path = "nsmod.sx", .data = "helper :: () -> s64 { 3 }\n" });
+    const main_src =
+        \\#import "a.sx";
+        \\#import "b.sx";
+        \\ns :: #import "nsmod.sx";
+        \\main :: () -> s32 { 0 }
+        \\
+    ;
+    try tmp.dir.writeFile(io, .{ .sub_path = "main.sx", .data = main_src });
+
+    var dirbuf: [4096]u8 = undefined;
+    const dirlen = try tmp.dir.realPath(io, &dirbuf);
+    const absdir = dirbuf[0..dirlen];
+
+    const main_path = try std.fmt.allocPrint(alloc, "{s}/main.sx", .{absdir});
+    const a_path = try std.fmt.allocPrint(alloc, "{s}/a.sx", .{absdir});
+    const b_path = try std.fmt.allocPrint(alloc, "{s}/b.sx", .{absdir});
+    const ns_path = try std.fmt.allocPrint(alloc, "{s}/nsmod.sx", .{absdir});
+
+    const main_bytes = try std.Io.Dir.readFileAlloc(.cwd(), io, main_path, alloc, .limited(1 << 20));
+    const main_source = try alloc.dupeZ(u8, main_bytes);
+    var p = parser.Parser.init(alloc, main_source);
+    const root = p.parse() catch return error.ParseFailed;
+
+    var chain = std.StringHashMap(void).init(alloc);
+    var cache = imports.ModuleCache.init(alloc);
+    var import_graph = std.StringHashMap(std.StringHashMap(void)).init(alloc);
+    var flat_import_graph = std.StringHashMap(std.StringHashMap(void)).init(alloc);
+    const stdlib_paths = [_][]const u8{};
+
+    const mod = try imports.resolveImports(
+        alloc,
+        io,
+        root,
+        absdir,
+        main_path,
+        &chain,
+        &cache,
+        null,
+        null,
+        &stdlib_paths,
+        &import_graph,
+        &flat_import_graph,
+        .{},
+    );
+
+    var module_fns = imports.ModuleFns.init(alloc);
+    try imports.buildModuleFns(alloc, main_path, mod, &cache, &module_fns);
+
+    // The MERGED scope the first-wins resolver consumes is unchanged: mergeFlat
+    // still drops the second `greet`, so `mod.decls` carries exactly ONE — and
+    // it is a.sx's author (the first flat import), not b.sx's.
+    var greet_count: usize = 0;
+    var merged_greet: ?*const ast.FnDecl = null;
+    for (mod.decls) |decl| {
+        const name = decl.data.declName() orelse continue;
+        if (!std.mem.eql(u8, name, "greet")) continue;
+        greet_count += 1;
+        if (decl.data == .fn_decl) merged_greet = &decl.data.fn_decl;
+    }
+    try std.testing.expectEqual(@as(usize, 1), greet_count);
+
+    // module_fns retains BOTH authors of `greet`, keyed by their own paths —
+    // the dropped author is recorded here (side index), not in the merged scope.
+    const a_fns = module_fns.get(a_path) orelse return error.MissingAFns;
+    const b_fns = module_fns.get(b_path) orelse return error.MissingBFns;
+    const a_greet = a_fns.get("greet") orelse return error.MissingAGreet;
+    const b_greet = b_fns.get("greet") orelse return error.MissingBGreet;
+    // Distinct authoring decls — not the same node deduped down to one.
+    try std.testing.expect(a_greet != b_greet);
+    // First-wins: the surviving merged-scope `greet` is a.sx's author.
+    try std.testing.expect(merged_greet == a_greet);
+
+    // flat_import_graph carries the two bare `#import` edges, NOT the
+    // namespaced `ns :: #import` edge.
+    const flat = flat_import_graph.get(main_path) orelse return error.MissingFlatEdges;
+    try std.testing.expect(flat.contains(a_path));
+    try std.testing.expect(flat.contains(b_path));
+    try std.testing.expect(!flat.contains(ns_path));
+
+    // The full import_graph DOES record the namespaced edge (the contrast that
+    // makes the flat-graph exclusion meaningful).
+    const full = import_graph.get(main_path) orelse return error.MissingFullEdges;
+    try std.testing.expect(full.contains(a_path));
+    try std.testing.expect(full.contains(b_path));
+    try std.testing.expect(full.contains(ns_path));
+}
+
+// Mixed collision: a.sx authors `Widget` as a STRUCT (non-fn), b.sx authors it
+// as a FUNCTION. fix-0102a must NOT let the function-author retention shift the
+// merged scope — first-wins keeps a.sx's struct and drops b.sx's function,
+// exactly as on `wt-fix-0102-base`. (The fn author may still be indexed in
+// module_fns; resolution is what must be untouched.)
+test "imports: mixed non-fn/fn same-name collision stays first-wins in merged scope" {
+    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
+    defer arena.deinit();
+    const alloc = arena.allocator();
+    const io = testIo();
+
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+
+    try tmp.dir.writeFile(io, .{ .sub_path = "a.sx", .data = "Widget :: struct { x: s64 }\n" });
+    try tmp.dir.writeFile(io, .{ .sub_path = "b.sx", .data = "Widget :: () -> s64 { 7 }\n" });
+    const main_src =
+        \\#import "a.sx";
+        \\#import "b.sx";
+        \\main :: () -> s32 { 0 }
+        \\
+    ;
+    try tmp.dir.writeFile(io, .{ .sub_path = "main.sx", .data = main_src });
+
+    var dirbuf: [4096]u8 = undefined;
+    const dirlen = try tmp.dir.realPath(io, &dirbuf);
+    const absdir = dirbuf[0..dirlen];
+    const main_path = try std.fmt.allocPrint(alloc, "{s}/main.sx", .{absdir});
+
+    const main_bytes = try std.Io.Dir.readFileAlloc(.cwd(), io, main_path, alloc, .limited(1 << 20));
+    const main_source = try alloc.dupeZ(u8, main_bytes);
+    var p = parser.Parser.init(alloc, main_source);
+    const root = p.parse() catch return error.ParseFailed;
+
+    var chain = std.StringHashMap(void).init(alloc);
+    var cache = imports.ModuleCache.init(alloc);
+    var import_graph = std.StringHashMap(std.StringHashMap(void)).init(alloc);
+    var flat_import_graph = std.StringHashMap(std.StringHashMap(void)).init(alloc);
+    const stdlib_paths = [_][]const u8{};
+
+    const mod = try imports.resolveImports(
+        alloc,
+        io,
+        root,
+        absdir,
+        main_path,
+        &chain,
+        &cache,
+        null,
+        null,
+        &stdlib_paths,
+        &import_graph,
+        &flat_import_graph,
+        .{},
+    );
+
+    // Exactly ONE `Widget` survives the merged scope, and it is a.sx's STRUCT —
+    // the function author did not displace or duplicate it.
+    var widget_count: usize = 0;
+    var merged_is_struct = false;
+    for (mod.decls) |decl| {
+        const name = decl.data.declName() orelse continue;
+        if (!std.mem.eql(u8, name, "Widget")) continue;
+        widget_count += 1;
+        merged_is_struct = decl.data == .struct_decl;
+    }
+    try std.testing.expectEqual(@as(usize, 1), widget_count);
+    try std.testing.expect(merged_is_struct);
+}

src/imports.zig

@@ -5,6 +5,18 @@ const errors = @import("errors.zig");
 const c_import = @import("c_import.zig");
 const Node = ast.Node;
 
+/// The `*const ast.FnDecl` a function-authoring decl carries, or null when the
+/// decl is not a function — either a bare `fn_decl` (`f :: (…) -> T { … }`) or a
+/// `const_decl` whose value is a function. Drives the per-module `module_fns`
+/// identity index (fix-0102a).
+fn fnDeclOf(decl: *const Node) ?*const ast.FnDecl {
+    return switch (decl.data) {
+        .fn_decl => &decl.data.fn_decl,
+        .const_decl => |cd| if (cd.value.data == .fn_decl) &cd.value.data.fn_decl else null,
+        else => null,
+    };
+}
+
 /// Comptime evaluation context for the inline-if hoisting pass below.
 /// Mirrors the values `injectComptimeConstants` will later push into the
 /// lowering's `comptime_constants` map (OS / ARCH / POINTER_SIZE), but
@@ -392,6 +404,43 @@ pub const ResolvedModule = struct {
 /// Module cache: maps resolved file paths to their ResolvedModules.
 pub const ModuleCache = std.StringHashMap(ResolvedModule);
 
+/// Per-module function identity index: function NAME → the `*const FnDecl` that
+/// module AUTHORS. Mirrors a single module's slice of `module_scopes`.
+pub const FnIndex = std.StringHashMap(*const ast.FnDecl);
+
+/// `path → name → *const FnDecl`, mirroring `module_scopes`. One entry per
+/// resolved module keyed by its path (a directory's combined module keyed by
+/// `dir_path`); each entry indexes only what that module AUTHORS. Two modules
+/// each authoring `f` are retained under their own paths — the identity index
+/// fix-0102c's bare-name disambiguation consults to bind a flat call to the
+/// right author.
+pub const ModuleFns = std.StringHashMap(FnIndex);
+
+/// Index a single module's authored functions (`own_decls`) into `out[path]`.
+/// First-wins WITHIN a module mirrors the scan pass; cross-module same-name
+/// authors live under their own `path` keys.
+fn indexModuleFns(allocator: std.mem.Allocator, out: *ModuleFns, path: []const u8, own_decls: []const *Node) !void {
+    const gop = try out.getOrPut(path);
+    if (!gop.found_existing) gop.value_ptr.* = FnIndex.init(allocator);
+    for (own_decls) |decl| {
+        const fd = fnDeclOf(decl) orelse continue;
+        const name = decl.data.declName() orelse continue;
+        if (gop.value_ptr.contains(name)) continue;
+        try gop.value_ptr.put(name, fd);
+    }
+}
+
+/// Build the per-module function index from a resolved program: the main module
+/// (keyed by `main_path`) plus every cached module (keyed by its own path).
+/// Mirrors how `core.zig` fills `module_scopes` from `mod.scope` + the cache.
+pub fn buildModuleFns(allocator: std.mem.Allocator, main_path: []const u8, main_mod: ResolvedModule, cache: *const ModuleCache, out: *ModuleFns) !void {
+    try indexModuleFns(allocator, out, main_path, main_mod.own_decls);
+    var it = cache.iterator();
+    while (it.next()) |entry| {
+        try indexModuleFns(allocator, out, entry.key_ptr.*, entry.value_ptr.own_decls);
+    }
+}
+
 pub fn resolveImports(
     allocator: std.mem.Allocator,
     io: std.Io,
@@ -404,6 +453,7 @@ pub fn resolveImports(
     diagnostics: ?*errors.DiagnosticList,
     stdlib_paths: []const []const u8,
     import_graph: ?*std.StringHashMap(std.StringHashMap(void)),
+    flat_import_graph: ?*std.StringHashMap(std.StringHashMap(void)),
     comptime_ctx: ComptimeContext,
 ) !ResolvedModule {
     // Record this file's edge set so `param_impl_map` lookups can filter
@@ -414,6 +464,15 @@ pub fn resolveImports(
             try g.put(file_path, std.StringHashMap(void).init(allocator));
         }
     }
+    // FLAT-only edge set: identical to `import_graph` but records ONLY bare
+    // `#import "…"` edges (`imp.name == null`), never a namespaced
+    // `ns :: #import "…"`. fix-0102c's bare-name disambiguation walks this to
+    // decide which same-name authors a flat importer can actually reach.
+    if (flat_import_graph) |g| {
+        if (!g.contains(file_path)) {
+            try g.put(file_path, std.StringHashMap(void).init(allocator));
+        }
+    }
     var mod = ResolvedModule{
         .path = file_path,
         .decls = &.{},
@@ -536,6 +595,17 @@ pub fn resolveImports(
                 set.put(resolved_path, {}) catch {};
             }
         }
+        // The same edge, FLAT-only: recorded only for a bare `#import`
+        // (`imp.name == null`), excluding a namespaced `ns :: #import`. Covers
+        // both a flat file import and a flat directory import (`resolved_path`
+        // is the directory in the latter case).
+        if (imp.name == null) {
+            if (flat_import_graph) |g| {
+                if (g.getPtr(file_path)) |set| {
+                    set.put(resolved_path, {}) catch {};
+                }
+            }
+        }
 
         // Circular import check — only along the current chain
         if (chain.contains(resolved_path)) continue;
@@ -563,7 +633,7 @@ pub fn resolveImports(
                 // Push onto chain before recursing, pop after
                 try chain.put(resolved_path, {});
                 const imp_dir = dirName(resolved_path);
-                const result = try resolveImports(allocator, io, imp_root, imp_dir, resolved_path, chain, cache, source_map, diagnostics, stdlib_paths, import_graph, comptime_ctx);
+                const result = try resolveImports(allocator, io, imp_root, imp_dir, resolved_path, chain, cache, source_map, diagnostics, stdlib_paths, import_graph, flat_import_graph, comptime_ctx);
                 _ = chain.remove(resolved_path);
 
                 // Cache
@@ -571,7 +641,7 @@ pub fn resolveImports(
                 break :blk result;
             } else |_| {
                 // File read failed — try as directory import
-                const result = resolveDirectoryImport(allocator, io, resolved_path, chain, cache, source_map, diagnostics, decl.span, stdlib_paths, import_graph, comptime_ctx) catch {
+                const result = resolveDirectoryImport(allocator, io, resolved_path, chain, cache, source_map, diagnostics, decl.span, stdlib_paths, import_graph, flat_import_graph, comptime_ctx) catch {
                     if (diagnostics) |diags| {
                         diags.addFmt(.err, decl.span, "cannot read import '{s}' (not a file or directory)", .{resolved_path});
                     }
@@ -605,6 +675,7 @@ fn resolveDirectoryImport(
     span: ast.Span,
     stdlib_paths: []const []const u8,
     import_graph: ?*std.StringHashMap(std.StringHashMap(void)),
+    flat_import_graph: ?*std.StringHashMap(std.StringHashMap(void)),
     comptime_ctx: ComptimeContext,
 ) anyerror!ResolvedModule {
     // Open the directory with iteration capability
@@ -679,7 +750,7 @@ fn resolveDirectoryImport(
             };
 
             try chain.put(file_path, {});
-            const result = try resolveImports(allocator, io, imp_root, dir_path, file_path, chain, cache, source_map, diagnostics, stdlib_paths, import_graph, comptime_ctx);
+            const result = try resolveImports(allocator, io, imp_root, dir_path, file_path, chain, cache, source_map, diagnostics, stdlib_paths, import_graph, flat_import_graph, comptime_ctx);
             _ = chain.remove(file_path);
 
             try cache.put(file_path, result);

src/ir/lower.test.zig

@@ -10,6 +10,9 @@ const Ref = ir_mod.Ref;
 const FuncId = ir_mod.FuncId;
 const Lowering = ir_mod.Lowering;
 
+const parser = @import("../parser.zig");
+const imports = @import("../imports.zig");
+
 test "lower: simple function with arithmetic" {
     const alloc = std.testing.allocator;
     var module = ir_mod.Module.init(alloc);
@@ -1264,3 +1267,180 @@ test "lower: reflectionArgIsType accepts spelled types, rejects plain values (is
     try std.testing.expect(!l.reflectionArgIsType(&float_node));
     try std.testing.expect(!l.reflectionArgIsType(&bool_node));
 }
+
+var g_lower_test_threaded: ?std.Io.Threaded = null;
+fn lowerTestIo() std.Io {
+    if (g_lower_test_threaded == null) {
+        g_lower_test_threaded = std.Io.Threaded.init(std.heap.page_allocator, .{});
+    }
+    return g_lower_test_threaded.?.io();
+}
+
+/// Count functions named `name` that carry a REAL body (promoted from the extern
+/// stub: not `is_extern`, at least one basic block).
+fn countRealBodies(module: *ir_mod.Module, name: []const u8) usize {
+    var n: usize = 0;
+    for (module.functions.items) |func| {
+        if (!std.mem.eql(u8, module.types.getString(func.name), name)) continue;
+        if (func.is_extern) continue;
+        if (func.blocks.items.len == 0) continue;
+        n += 1;
+    }
+    return n;
+}
+
+// fix-0102b: two flat-imported modules each author `greet`. The first-wins merge
+// keeps a.sx's author in the merged decl list (the WINNER) and drops b.sx's,
+// which `module_fns` still retains (0102a). `main` itself can't bare-call `greet`
+// — under fix-0102c two flat authors make that ambiguous — so it calls a.sx's
+// `use_greet` wrapper, whose own-author call to `greet` binds a.sx's winner.
+// BEFORE the identity-addressable pass, only the winner has a real body — the
+// shadowed author has no slot at all (the pre-fix symptom: one `greet`).
+// `lowerRetainedSameNameAuthors` declares the shadowed author its OWN same-name
+// FuncId and lowers its body there, so BOTH authors carry distinct, non-extern
+// bodies, and `resolveFuncByName` still returns the winner (the name-keyed slot).
+test "lower: shadowed same-name author gets its own FuncId + real body (fix-0102b)" {
+    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
+    defer arena.deinit();
+    const alloc = arena.allocator();
+    const io = lowerTestIo();
+
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+
+    try tmp.dir.writeFile(io, .{ .sub_path = "a.sx", .data = "greet :: () -> s64 { 1 }\nuse_greet :: () -> s64 { greet() }\n" });
+    try tmp.dir.writeFile(io, .{ .sub_path = "b.sx", .data = "greet :: () -> s64 { 2 }\n" });
+    const main_src =
+        \\#import "a.sx";
+        \\#import "b.sx";
+        \\main :: () -> s64 { use_greet() }
+        \\
+    ;
+    try tmp.dir.writeFile(io, .{ .sub_path = "main.sx", .data = main_src });
+
+    var dirbuf: [4096]u8 = undefined;
+    const dirlen = try tmp.dir.realPath(io, &dirbuf);
+    const absdir = dirbuf[0..dirlen];
+
+    const main_path = try std.fmt.allocPrint(alloc, "{s}/main.sx", .{absdir});
+    const main_bytes = try std.Io.Dir.readFileAlloc(.cwd(), io, main_path, alloc, .limited(1 << 20));
+    const main_source = try alloc.dupeZ(u8, main_bytes);
+    var p = parser.Parser.init(alloc, main_source);
+    const root = p.parse() catch return error.ParseFailed;
+
+    var chain = std.StringHashMap(void).init(alloc);
+    var cache = imports.ModuleCache.init(alloc);
+    var import_graph = std.StringHashMap(std.StringHashMap(void)).init(alloc);
+    var flat_import_graph = std.StringHashMap(std.StringHashMap(void)).init(alloc);
+    const stdlib_paths = [_][]const u8{};
+
+    const mod = try imports.resolveImports(
+        alloc,
+        io,
+        root,
+        absdir,
+        main_path,
+        &chain,
+        &cache,
+        null,
+        null,
+        &stdlib_paths,
+        &import_graph,
+        &flat_import_graph,
+        .{},
+    );
+
+    // Per-module visibility scopes + authored-function index, wired exactly as
+    // `core.zig` does before `lowerRoot`.
+    var module_scopes = std.StringHashMap(std.StringHashMap(void)).init(alloc);
+    try module_scopes.put(main_path, mod.scope);
+    var cache_it = cache.iterator();
+    while (cache_it.next()) |entry| {
+        try module_scopes.put(entry.key_ptr.*, entry.value_ptr.scope);
+    }
+    var module_fns = imports.ModuleFns.init(alloc);
+    try imports.buildModuleFns(alloc, main_path, mod, &cache, &module_fns);
+
+    const resolved_root = try alloc.create(Node);
+    resolved_root.* = .{ .span = root.span, .data = .{ .root = .{ .decls = mod.decls } } };
+
+    var module = ir_mod.Module.init(alloc);
+    defer module.deinit();
+    var diagnostics = errors.DiagnosticList.init(alloc, main_source, main_path);
+    var lowering = Lowering.init(&module);
+    lowering.main_file = main_path;
+    lowering.resolved_root = resolved_root;
+    lowering.diagnostics = &diagnostics;
+    lowering.program_index.module_scopes = &module_scopes;
+    lowering.program_index.import_graph = &import_graph;
+    lowering.program_index.flat_import_graph = &flat_import_graph;
+    lowering.program_index.module_fns = &module_fns;
+
+    lowering.lowerRoot(resolved_root);
+    try std.testing.expect(!diagnostics.hasErrors());
+
+    // Pre-fix symptom: only the winner `greet` (a.sx) has a real body — lowered
+    // because `main` calls it; the shadowed author (b.sx) was dropped entirely.
+    try std.testing.expectEqual(@as(usize, 1), countRealBodies(&module, "greet"));
+
+    // Identity-addressable pass: the shadowed author gets its OWN FuncId + body.
+    lowering.lowerRetainedSameNameAuthors();
+    try std.testing.expect(!diagnostics.hasErrors());
+
+    // Both `greet` authors now carry distinct, real (non-extern) bodies, and the
+    // two FuncIds are distinct.
+    try std.testing.expectEqual(@as(usize, 2), countRealBodies(&module, "greet"));
+
+    const name_id = module.types.internString("greet");
+    var first: ?FuncId = null;
+    var second: ?FuncId = null;
+    for (module.functions.items, 0..) |func, i| {
+        if (func.name != name_id) continue;
+        if (func.is_extern or func.blocks.items.len == 0) continue;
+        if (first == null) first = FuncId.fromIndex(@intCast(i)) else second = FuncId.fromIndex(@intCast(i));
+    }
+    try std.testing.expect(first != null and second != null);
+    try std.testing.expect(first.? != second.?);
+
+    // F1 (attempt-2): the identity map must be keyed by the STABLE AST field
+    // pointer for BOTH same-name authors — the exact pointers `fn_ast_map` and
+    // `module_fns` carry — not a per-iteration switch-capture temporary. If the
+    // winner were keyed by `&fd` (the scanDecls bug), this lookup by the stable
+    // `fn_ast_map` pointer would miss (null). fix-0102c routes calls through
+    // exactly these pointers, so the round-trip must hold here.
+    const winner_fd = lowering.program_index.fn_ast_map.get("greet").?;
+    const winner_fid = lowering.fn_decl_fids.get(winner_fd);
+    try std.testing.expect(winner_fid != null);
+    // Round-trips to the first-wins winner FuncId (resolveFuncByName's pick).
+    try std.testing.expectEqual(lowering.resolveFuncByName("greet").?, winner_fid.?);
+
+    // The shadowed author's stable pointer lives in `module_fns`; find the one
+    // that is NOT the winner and confirm IT round-trips to a DISTINCT FuncId.
+    var shadow_fd: ?*const ast.FnDecl = null;
+    var mf_it = module_fns.iterator();
+    while (mf_it.next()) |path_entry| {
+        if (path_entry.value_ptr.get("greet")) |fd| {
+            if (fd != winner_fd) shadow_fd = fd;
+        }
+    }
+    try std.testing.expect(shadow_fd != null);
+    const shadow_fid = lowering.fn_decl_fids.get(shadow_fd.?);
+    try std.testing.expect(shadow_fid != null);
+    try std.testing.expect(shadow_fid.? != winner_fid.?);
+
+    // fix-0102c: THE bare-name resolver routes per caller file. `main` flat-
+    // imports two `greet` authors and is its own author of neither → a bare
+    // `greet()` from `main` is ambiguous. a.sx authors the WINNER, so its bare
+    // `greet` resolves through the existing path (`.none`). b.sx authors the
+    // SHADOW, so own-author-wins binds b.sx's distinct FuncId — not first-wins.
+    const a_path = try std.fmt.allocPrint(alloc, "{s}/a.sx", .{absdir});
+    const b_path = try std.fmt.allocPrint(alloc, "{s}/b.sx", .{absdir});
+    try std.testing.expect(lowering.resolveBareCallee("greet", main_path) == .ambiguous);
+    try std.testing.expect(lowering.resolveBareCallee("greet", a_path) == .none);
+    switch (lowering.resolveBareCallee("greet", b_path)) {
+        .func => |resolved| try std.testing.expectEqual(shadow_fid.?, resolved.fid),
+        else => return error.TestUnexpectedResult,
+    }
+    // A name no module authors (and no flat import provides) never routes.
+    try std.testing.expect(lowering.resolveBareCallee("nonexistent", b_path) == .none);
+}

src/ir/lower.zig

@@ -126,6 +126,17 @@ pub const Lowering = struct {
     comptime_param_nodes: ?std.StringHashMap(*const Node) = null, // active comptime substitutions
     target_type: ?TypeId = null, // target type for struct/enum literals without explicit names
     lowered_functions: std.StringHashMap(void), // tracks which functions have been fully lowered
+    /// Identity map: authoring `*const ast.FnDecl` → the FuncId `declareFunction`
+    /// created for it. The name-keyed function table (`resolveFuncByName`) returns
+    /// the FIRST author of a name, so two same-name authors collide there; this
+    /// map addresses each author's OWN slot by decl identity (fix-0102b), letting
+    /// a SHADOWED author lower its body into a distinct FuncId.
+    fn_decl_fids: std.AutoHashMap(*const ast.FnDecl, FuncId),
+    /// FuncId-keyed lowered tracking — the identity twin of `lowered_functions`
+    /// (which keys by name). A shadowed same-name author shares the winner's name
+    /// but not its FuncId, so name-keyed tracking can't tell them apart; this
+    /// records which specific FuncIds have had a real body lowered (fix-0102b).
+    lowered_fids: std.AutoHashMap(FuncId, void),
     local_fn_counter: u32 = 0, // unique counter for mangling local function names
     /// Declaration-name / import / visibility facts (architecture phase A1,
     /// `ProgramIndex`). Owns `import_flags`; borrows `module_scopes` /
@@ -286,12 +297,89 @@ pub const Lowering = struct {
         ret_var_name: ?[]const u8,
     };
 
+    /// Caller-state protection for lowering a function body re-entrantly — a
+    /// lazily lowered callee, a qualified `ns.fn` alias, or an out-of-line
+    /// same-name author. `enter` snapshots the in-progress builder / scope /
+    /// flag / pack / jni state and installs a fresh set for the nested body;
+    /// `restore` puts the caller's state back. Lowering a callee must be
+    /// transparent to the caller's own lowering — notably `block_terminated`,
+    /// which leaking back would mark the caller's trailing statements
+    /// dead-after-terminator (issue 0100 F2).
+    const FnBodyReentry = struct {
+        l: *Lowering,
+        func: ?FuncId,
+        block: ?BlockId,
+        counter: u32,
+        scope: ?*Scope,
+        defer_base: usize,
+        block_terminated: bool,
+        force_block_value: bool,
+        source_file: ?[]const u8,
+        jni_env_base: usize,
+        pack_arg_nodes: ?std.StringHashMap([]const *const Node),
+        pack_param_count: ?std.StringHashMap(u32),
+        pack_arg_types: ?std.StringHashMap([]const TypeId),
+        inline_return_target: ?InlineReturnInfo,
+
+        fn enter(l: *Lowering) FnBodyReentry {
+            const g = FnBodyReentry{
+                .l = l,
+                .func = l.builder.func,
+                .block = l.builder.current_block,
+                .counter = l.builder.inst_counter,
+                .scope = l.scope,
+                .defer_base = l.func_defer_base,
+                .block_terminated = l.block_terminated,
+                .force_block_value = l.force_block_value,
+                .source_file = l.current_source_file,
+                .jni_env_base = l.jni_env_stack_base,
+                .pack_arg_nodes = l.pack_arg_nodes,
+                .pack_param_count = l.pack_param_count,
+                .pack_arg_types = l.pack_arg_types,
+                .inline_return_target = l.inline_return_target,
+            };
+            // The `#jni_env` Ref stack is lexical to ONE function's instruction
+            // stream; move the visible base to the current top. Pack-fn mono
+            // state is likewise lexical to the pack-fn body — null it so a
+            // callee sharing a param NAME with the active pack doesn't fold the
+            // outer mono's arity into its own `<name>.len`.
+            l.jni_env_stack_base = l.jni_env_stack.items.len;
+            l.pack_arg_nodes = null;
+            l.pack_param_count = null;
+            l.pack_arg_types = null;
+            l.inline_return_target = null;
+            l.func_defer_base = l.defer_stack.items.len;
+            l.block_terminated = false;
+            l.force_block_value = false;
+            return g;
+        }
+
+        fn restore(g: FnBodyReentry) void {
+            const l = g.l;
+            l.setCurrentSourceFile(g.source_file);
+            l.scope = g.scope;
+            l.func_defer_base = g.defer_base;
+            l.block_terminated = g.block_terminated;
+            l.force_block_value = g.force_block_value;
+            l.builder.func = g.func;
+            l.builder.current_block = g.block;
+            l.builder.inst_counter = g.counter;
+            l.jni_env_stack_base = g.jni_env_base;
+            l.pack_arg_nodes = g.pack_arg_nodes;
+            l.pack_param_count = g.pack_param_count;
+            l.pack_arg_types = g.pack_arg_types;
+            l.inline_return_target = g.inline_return_target;
+        }
+    };
+
     pub fn init(module: *Module) Lowering {
         return .{
             .module = module,
             .builder = Builder.init(module),
             .alloc = module.alloc,
             .lowered_functions = std.StringHashMap(void).init(module.alloc),
+            .fn_decl_fids = std.AutoHashMap(*const ast.FnDecl, FuncId).init(module.alloc),
+            .lowered_fids = std.AutoHashMap(FuncId, void).init(module.alloc),
             .program_index = ProgramIndex.init(module.alloc),
         };
     }
@@ -703,8 +791,14 @@ pub const Lowering = struct {
                         self.program_index.fn_ast_map.put(fd.name, &decl.data.fn_decl) catch {};
                         self.program_index.import_flags.put(fd.name, is_imported) catch {};
                     }
-                    // Declare extern stub for all functions (bodies lowered lazily)
-                    self.declareFunction(&fd, fd.name);
+                    // Declare extern stub for all functions (bodies lowered
+                    // lazily). Key the identity map (`fn_decl_fids`, inside
+                    // `declareFunction`) by the STABLE AST field pointer — the
+                    // same `&decl.data.fn_decl` stored in `fn_ast_map` and
+                    // `module_fns` — not the switch-capture copy `fd`, whose
+                    // address is a per-iteration stack temporary that no later
+                    // decl-identity lookup can reproduce.
+                    self.declareFunction(&decl.data.fn_decl, fd.name);
                 },
                 .const_decl => |cd| {
                     if (cd.value.data == .fn_decl) {
@@ -1339,6 +1433,14 @@ pub const Lowering = struct {
     /// Pass 2: Lower main function body and comptime side-effects.
     fn lowerMainAndComptime(self: *Lowering, decls: []const *const Node) void {
         for (decls) |decl| {
+            // A `#run` body lowers in its OWN module's source context (fix-0102d
+            // site 4): `NAME :: #run f()` written in an imported module must
+            // resolve a bare `f` from that module's flat imports, not the main
+            // file's. Without this, `resolveBareCallee` runs with the main
+            // file's perspective and reports a genuine per-source author as
+            // ambiguous. Mirrors `scanDecls` / `lowerDecls`, which already set
+            // the source file per decl.
+            self.setCurrentSourceFile(decl.source_file);
             switch (decl.data) {
                 .const_decl => |cd| {
                     if (cd.value.data == .fn_decl) {
@@ -1367,6 +1469,174 @@ pub const Lowering = struct {
         }
     }
 
+    /// Lower every SHADOWED same-name function author into its OWN FuncId with a
+    /// real (non-extern) body — the identity-addressable lowering PATH this step
+    /// adds (fix-0102b). It does NOT run during a default compile: the name path
+    /// stays the sole resolver, so the suite is byte-for-byte unchanged. fix-0102c
+    /// invokes it as part of routing bare flat calls to the right author; until
+    /// then it is exercised by the lower-test regression that asserts two distinct
+    /// non-extern bodies for a same-name collision.
+    ///
+    /// The first-wins flat/directory merge keeps exactly one author per name in
+    /// the merged decl list; `scanDecls` declares that WINNER (lowered on demand
+    /// through the name-keyed `lazyLowerFunction`). fix-0102a retained every
+    /// dropped same-name author in `module_fns` (path → name → `*FnDecl`) without
+    /// touching resolution; this walks that index and gives each shadowed author
+    /// its own slot: `declareFunction` (identity-mapped to a fresh same-name
+    /// FuncId) + `lowerFunctionBodyInto` (its body, in its own module's
+    /// visibility context). Two same-name authors then carry distinct FuncIds and
+    /// distinct bodies, while `resolveFuncByName` still returns the first (winner)
+    /// author so existing calls bind first-wins.
+    ///
+    /// Scoped to DIRECT flat imports of the main file: a `module_fns` entry whose
+    /// path is the main file or one of its bare `#import` edges. A namespaced
+    /// (`ns :: #import`) author has no bare-name winner and is excluded both by
+    /// that flat-edge gate and by the `fn_ast_map` winner lookup below.
+    pub fn lowerRetainedSameNameAuthors(self: *Lowering) void {
+        const module_fns = self.program_index.module_fns orelse return;
+        const main_file = self.main_file orelse return;
+        const flat_graph = self.program_index.flat_import_graph orelse return;
+        const main_flat_edges = flat_graph.get(main_file);
+
+        var path_it = module_fns.iterator();
+        while (path_it.next()) |path_entry| {
+            const path = path_entry.key_ptr.*;
+            const is_eligible = std.mem.eql(u8, path, main_file) or
+                (main_flat_edges != null and main_flat_edges.?.contains(path));
+            if (!is_eligible) continue;
+
+            var fn_it = path_entry.value_ptr.iterator();
+            while (fn_it.next()) |fn_entry| {
+                const name = fn_entry.key_ptr.*;
+                const fd = fn_entry.value_ptr.*;
+
+                // A name with no bare winner is namespaced-only (`ns.fn`) — it
+                // never participated in the flat merge, so it has no shadow to
+                // lower. The author already owning the name-keyed slot (the
+                // first-wins winner) lowers through the normal lazy path.
+                const winner = self.program_index.fn_ast_map.get(name) orelse continue;
+                if (winner == fd) continue;
+
+                // Only plain free functions get an out-of-line slot; generic /
+                // foreign / builtin / #compiler authors keep their existing
+                // dispatch (mirrors lazyLowerFunction / declareFunction guards).
+                if (!isPlainFreeFn(fd)) continue;
+
+                _ = self.bareAuthorFuncId(fd, name, path);
+            }
+        }
+    }
+
+    /// Result of bare-call disambiguation (fix-0102c).
+    pub const BareCallee = union(enum) {
+        /// Bind the call to this specific author — its identity-addressable
+        /// FuncId (fix-0102b's `bareAuthorFuncId`) AND its `*FnDecl`. The decl
+        /// travels with the FuncId so every callee-signature decision in the
+        /// call path (variadic packing, …) reads the RESOLVED author, never a
+        /// first-wins re-lookup by name (fix-0102c F1).
+        func: ResolvedAuthor,
+        /// ≥2 distinct flat authors are reachable from the caller and none is
+        /// the caller's own — the bare call can't pick one; require a qualifier.
+        ambiguous,
+        /// 0 or 1 reachable author, or the resolved author IS the existing
+        /// bare-name winner — defer to the existing path, byte-for-byte.
+        none,
+    };
+
+    /// A resolved bare-call author: its FuncId and the `*FnDecl` that defined
+    /// it, kept together so the call path has ONE source of truth for the
+    /// callee (no re-fetch by name after resolution).
+    pub const ResolvedAuthor = struct { fid: FuncId, decl: *const ast.FnDecl };
+
+    /// THE bare-name call resolver (fix-0102c). One canonical traversal over
+    /// fix-0102a's `module_fns` + `flat_import_graph` that routes a bare
+    /// identifier call `name` from `caller_file` to the right same-name author
+    /// when flat imports introduce a genuine collision. Every single-author /
+    /// local / parameter / std / qualified name resolves through the EXISTING
+    /// path unchanged: the resolver returns `.none` whenever the outcome would
+    /// match first-wins, so nothing on the common path is perturbed.
+    ///
+    /// - **own-author wins**: if `caller_file` authors `name` and the bare-name
+    ///   first-wins winner is a DIFFERENT author, bind the caller's own author.
+    ///   (When the winner already IS the caller's own — the single-author and
+    ///   first-importer cases — `.none` lets the existing path bind it.)
+    /// - else collect the authors reachable via `caller_file`'s FLAT import
+    ///   edges (bare `#import` of a file or directory, never a namespaced
+    ///   `ns :: #import`), deduped by `FnDecl` identity (a diamond import of the
+    ///   same module is one author): `≥2 distinct` → `.ambiguous`; exactly one
+    ///   that DIFFERS from the winner → bind it; otherwise `.none`.
+    ///
+    /// Generic / comptime / foreign / builtin authors are never rerouted — the
+    /// existing dispatch owns those shapes — so the resolver returns `.none`.
+    pub fn resolveBareCallee(self: *Lowering, name: []const u8, caller_file: []const u8) BareCallee {
+        const module_fns = self.program_index.module_fns orelse return .none;
+        const winner = self.program_index.fn_ast_map.get(name);
+
+        // own-author wins.
+        if (module_fns.get(caller_file)) |own_fns| {
+            if (own_fns.get(name)) |own| {
+                if (winner != null and winner.? == own) return .none;
+                if (!isPlainFreeFn(own)) return .none;
+                return .{ .func = .{ .fid = self.bareAuthorFuncId(own, name, caller_file), .decl = own } };
+            }
+        }
+
+        // Caller does not author `name` → collect its flat-reachable authors.
+        const flat_graph = self.program_index.flat_import_graph orelse return .none;
+        const edges = flat_graph.get(caller_file) orelse return .none;
+        var distinct = std.AutoHashMap(*const ast.FnDecl, []const u8).init(self.alloc);
+        defer distinct.deinit();
+        var edge_it = edges.iterator();
+        while (edge_it.next()) |e| {
+            const fns = module_fns.get(e.key_ptr.*) orelse continue;
+            // Only plain free functions are eligible for rerouting; generic /
+            // foreign / builtin / #compiler authors keep their existing
+            // dispatch. Filtering BEFORE the count gate means a same-name
+            // collision of non-plain authors (e.g. two flat-imported modules
+            // each `#foreign`ing the same symbol) is NOT counted as ambiguous —
+            // it falls through to `.none` and the existing first-wins path.
+            if (fns.get(name)) |fd| {
+                if (!isPlainFreeFn(fd)) continue;
+                distinct.put(fd, e.key_ptr.*) catch {};
+            }
+        }
+        if (distinct.count() == 0) return .none;
+        if (distinct.count() >= 2) return .ambiguous;
+
+        var one_it = distinct.iterator();
+        const entry = one_it.next().?;
+        const the_one = entry.key_ptr.*;
+        const the_path = entry.value_ptr.*;
+        if (winner != null and winner.? == the_one) return .none;
+        return .{ .func = .{ .fid = self.bareAuthorFuncId(the_one, name, the_path), .decl = the_one } };
+    }
+
+    /// The FuncId for a resolved bare-call author, ensuring its body is lowered.
+    /// Only ever called for a SHADOW (an author that is not the name-keyed
+    /// winner): the winner owns the name-keyed slot and lowers through the
+    /// normal lazy path, so `resolveBareCallee` returns `.none` for it. A shadow
+    /// is declared a fresh same-name FuncId in its OWN module's visibility
+    /// context and its body lowered into that slot via fix-0102b's identity-
+    /// addressable `lowerFunctionBodyInto`. Idempotent: `lowered_fids` tracks
+    /// which slots already carry a body.
+    fn bareAuthorFuncId(self: *Lowering, fd: *const ast.FnDecl, name: []const u8, path: []const u8) FuncId {
+        if (self.fn_decl_fids.get(fd)) |fid| {
+            if (!self.lowered_fids.contains(fid)) {
+                self.lowered_fids.put(fid, {}) catch {};
+                self.lowerFunctionBodyInto(fd, fid, name);
+            }
+            return fid;
+        }
+        const saved_src = self.current_source_file;
+        self.setCurrentSourceFile(path);
+        self.declareFunction(fd, name);
+        self.setCurrentSourceFile(saved_src);
+        const fid = self.fn_decl_fids.get(fd).?;
+        self.lowered_fids.put(fid, {}) catch {};
+        self.lowerFunctionBodyInto(fd, fid, name);
+        return fid;
+    }
+
     /// Declare a function as an extern stub (signature only, no body).
     pub fn declareFunction(self: *Lowering, fd: *const ast.FnDecl, name: []const u8) void {
         // Skip generic templates — they're monomorphized on demand, not declared as extern
@@ -1421,6 +1691,7 @@ pub const Lowering = struct {
                 func.is_variadic = is_variadic;
                 func.has_implicit_ctx = wants_ctx;
                 self.foreign_name_map.put(name, c_name) catch {};
+                self.fn_decl_fids.put(fd, fid) catch {};
                 return;
             }
         }
@@ -1432,6 +1703,7 @@ pub const Lowering = struct {
         func.source_file = self.current_source_file;
         func.is_variadic = is_variadic;
         func.has_implicit_ctx = wants_ctx;
+        self.fn_decl_fids.put(fd, fid) catch {};
     }
 
     /// Register a namespaced import's OWN functions under their module-qualified
@@ -1581,73 +1853,11 @@ pub const Lowering = struct {
         // Mark as lowered before lowering (prevents infinite recursion)
         self.lowered_functions.put(name, {}) catch {};
 
-        // Save builder state (same pattern as lambda lowering)
-        const saved_func = self.builder.func;
-        const saved_block = self.builder.current_block;
-        const saved_counter = self.builder.inst_counter;
-        const saved_scope = self.scope;
-        const saved_defer_base = self.func_defer_base;
-        const saved_block_terminated = self.block_terminated;
-        const saved_force_block_value = self.force_block_value;
-        const saved_source_file = self.current_source_file;
-        // Lowering a callee must be transparent to the caller's lowering
-        // state: restore the FULL saved context on EVERY exit path through one
-        // defer so the three exits (non-null branch, already-promoted early
-        // return, null-FuncId `ns.fn` alias branch) cannot drift. Notably
-        // `block_terminated` — a qualified alias whose body terminates (e.g. a
-        // constant-folded `if true { return … }`) leaves it true, and leaking
-        // that into the caller marks the caller's own trailing statements
-        // dead-after-terminator (issue 0100 F2). The jni/pack/foreign-class
-        // fields keep their own defers above.
-        defer {
-            self.setCurrentSourceFile(saved_source_file);
-            self.scope = saved_scope;
-            self.func_defer_base = saved_defer_base;
-            self.block_terminated = saved_block_terminated;
-            self.force_block_value = saved_force_block_value;
-            self.builder.func = saved_func;
-            self.builder.current_block = saved_block;
-            self.builder.inst_counter = saved_counter;
-        }
-        // The `#jni_env` Ref stack is lexical within ONE function's instruction
-        // stream — Refs from the caller don't dereference correctly in this
-        // callee's body. Move the visible base to the current top so
-        // omitted-env `#jni_call` in this fn doesn't accidentally pick up the
-        // caller's Refs. Defer covers all the early-return paths below.
-        const saved_jni_env_base = self.jni_env_stack_base;
-        self.jni_env_stack_base = self.jni_env_stack.items.len;
-        defer self.jni_env_stack_base = saved_jni_env_base;
-        // Pack-fn mono state is lexical to the pack-fn body. A lazily
-        // lowered callee may share a param NAME with the active pack
-        // (e.g. `walk(args: []Any)` called from `probe(..$args)`); without
-        // isolation, `lowerFieldAccess`'s `<pack_name>.len` intercept
-        // folds the callee's `args.len` to the outer mono's arity and
-        // bakes the constant into the IR. Same shape for the AST-node
-        // and per-element-type maps. Null out for the duration of the
-        // body lowering and restore on exit.
-        const saved_pan = self.pack_arg_nodes;
-        const saved_ppc = self.pack_param_count;
-        const saved_pat = self.pack_arg_types;
-        const saved_iri = self.inline_return_target;
-        self.pack_arg_nodes = null;
-        self.pack_param_count = null;
-        self.pack_arg_types = null;
-        self.inline_return_target = null;
-        defer {
-            self.pack_arg_nodes = saved_pan;
-            self.pack_param_count = saved_ppc;
-            self.pack_arg_types = saved_pat;
-            self.inline_return_target = saved_iri;
-        }
-        self.func_defer_base = self.defer_stack.items.len;
-        self.block_terminated = false;
-        self.force_block_value = false;
-
-        // Find the existing extern stub and replace it with a full body
+        // Find the existing extern stub (from scanDecls), keyed by NAME — the
+        // FIRST author of a name owns this slot. A shadowed same-name author is
+        // not here (it has no name-keyed slot); it is lowered out-of-line into
+        // its OWN FuncId by `lowerRetainedSameNameAuthors` (fix-0102b).
         const name_id = self.module.types.internString(name);
-        const ret_ty = self.resolveReturnType(fd);
-
-        // Look up the existing function declaration (from scanDecls)
         var func_id: ?FuncId = null;
         for (self.module.functions.items, 0..) |func, i| {
             if (func.name == name_id) {
@@ -1656,100 +1866,118 @@ pub const Lowering = struct {
             }
         }
 
-        if (func_id == null) {
-            // Function not yet declared — create it fresh via lowerFunction.
-            // A module-qualified alias (`ns.fn`, issue 0100) is registered in
-            // `fn_ast_map` without an eager `declareFunction`, so there's no
-            // `Function.source_file` to switch to (the path above). Restore the
-            // alias's OWN declaring source before lowering its body, otherwise
-            // it lowers in the caller's visibility context and an own-import
-            // callee (`foo` calling `helper` from `foo`'s module's flat import)
-            // is reported "not visible" (issue 0100 F1).
-            if (self.program_index.qualified_fn_source.get(name)) |src| {
-                self.setCurrentSourceFile(src);
-            }
-            self.lowerFunction(fd, name, false);
-            return; // caller state restored by the top-level defer
-        }
-
         if (func_id) |fid| {
-            // Re-use the existing function slot — switch builder to it
-            self.builder.func = fid;
-            const func = &self.module.functions.items[@intFromEnum(fid)];
-            self.setCurrentSourceFile(func.source_file);
-            if (!func.is_extern) {
-                // Already promoted (e.g., via lowerComptimeDeps) — skip.
-                // Caller state restored by the top-level defer.
-                return;
-            }
-            func.is_extern = false; // promote from extern stub to real function
-            func.linkage = if (isExportedEntryName(name)) .external else .internal;
-            if (fd.call_conv == .c) func.call_conv = .c;
-            // Set inst_counter to param count (params occupy refs 0..N-1).
-            // IR params = AST params + 1 if the function carries `__sx_ctx`
-            // at slot 0.
-            const ctx_slots: usize = if (func.has_implicit_ctx) 1 else 0;
-            std.debug.assert(func.params.len == fd.params.len + ctx_slots);
-            self.builder.inst_counter = @intCast(func.params.len);
-
-            // Create entry block
-            const entry_name = self.module.types.internString("entry");
-            const entry = self.builder.appendBlock(entry_name, &.{});
-            self.builder.switchToBlock(entry);
-
-            // Create scope and bind params
-            var scope = Scope.init(self.alloc, null);
-            defer scope.deinit();
-            self.scope = &scope;
-
-            // The implicit `__sx_ctx` param (when present) lives at slot 0;
-            // user params shift by one. `current_ctx_ref` is bound to slot 0
-            // so call-site lowering can prepend it to every sx-to-sx call.
-            // For OS-called entry points (main / JNI hooks), there's no
-            // ctx param at all — we synthesise `&__sx_default_context` and
-            // bind `current_ctx_ref` to its address so the body's sx-to-sx
-            // calls have a sensible Context to forward.
-            const wants_ctx = self.funcWantsImplicitCtx(fd);
-            const saved_ctx_ref = self.current_ctx_ref;
-            defer self.current_ctx_ref = saved_ctx_ref;
-            const user_param_base: u32 = if (wants_ctx) 1 else 0;
-            if (wants_ctx) self.current_ctx_ref = Ref.fromIndex(0);
-
-            for (fd.params, 0..) |p, i| {
-                const pty = self.resolveParamType(&p);
-                const slot = self.builder.alloca(pty);
-                const param_ref = Ref.fromIndex(@intCast(i + user_param_base));
-                self.builder.store(slot, param_ref);
-                scope.put(p.name, .{ .ref = slot, .ty = pty, .is_alloca = true });
-            }
-
-            // Inbound entry points and callconv(.c) sx functions: bind
-            // current_ctx_ref to the static default before any user code
-            // runs. C-callable sx functions don't get a __sx_ctx param,
-            // but their bodies may call ctx-aware sx functions / fn-ptrs
-            // and need a real Context to forward.
-            if (!wants_ctx and self.implicit_ctx_enabled) {
-                if (self.program_index.global_names.get("__sx_default_context")) |dctx_gi| {
-                    self.current_ctx_ref = self.builder.emit(.{ .global_addr = dctx_gi.id }, self.module.types.ptrTo(.void));
-                }
-            }
-
-            // Lower the function body (set target_type to return type for implicit returns)
-            const saved_target = self.target_type;
-            self.target_type = if (ret_ty != .void and ret_ty != .noreturn) ret_ty else null;
-            if (ret_ty != .void and ret_ty != .noreturn) {
-                self.lowerValueBody(fd.body, ret_ty);
-            } else {
-                // void / noreturn: no value to return — lower as statements and
-                // let `ensureTerminator` close the block (ret void / unreachable).
-                self.lowerBlock(fd.body);
-                self.ensureTerminator(ret_ty);
-            }
-            self.target_type = saved_target;
-
-            self.builder.finalize();
+            self.lowerFunctionBodyInto(fd, fid, name);
+            return;
         }
-        // Caller state restored by the top-level defer.
+
+        // Function not yet declared — create it fresh via lowerFunction. A
+        // module-qualified alias (`ns.fn`, issue 0100) is registered in
+        // `fn_ast_map` without an eager `declareFunction`, so there's no
+        // `Function.source_file` to switch to. Restore the alias's OWN declaring
+        // source before lowering its body, otherwise it lowers in the caller's
+        // visibility context and an own-import callee (`foo` calling `helper`
+        // from `foo`'s module's flat import) is reported "not visible" (0100 F1).
+        // The reentry guard keeps the nested lowering transparent to the caller.
+        var reentry = FnBodyReentry.enter(self);
+        defer reentry.restore();
+        if (self.program_index.qualified_fn_source.get(name)) |src| {
+            self.setCurrentSourceFile(src);
+        }
+        self.lowerFunction(fd, name, false);
+    }
+
+    /// Lower `fd`'s body into the SPECIFIC `fid`, promoting its extern stub to a
+    /// real function. Identity-addressable: the caller passes the exact FuncId,
+    /// so a SHADOWED same-name author lowers into its OWN slot instead of
+    /// colliding on the name-keyed `resolveFuncByName` (which returns the first
+    /// author, the very split that trips issue 0100's param-count assert). Self-
+    /// contained — the `FnBodyReentry` guard makes the nested lowering
+    /// transparent to any in-progress caller body (issue 0100 F2) — so it serves
+    /// both `lazyLowerFunction`'s name-keyed found path and the out-of-line
+    /// `lowerRetainedSameNameAuthors` pass.
+    fn lowerFunctionBodyInto(self: *Lowering, fd: *const ast.FnDecl, fid: FuncId, name: []const u8) void {
+        // objc-defined-class method context for `*Self` substitution (M1.2 A.2b);
+        // the resolveReturnType / resolveParamType calls below consult it.
+        const saved_fc = self.current_foreign_class;
+        defer self.current_foreign_class = saved_fc;
+        if (self.lookupObjcDefinedClassForMethod(name)) |fcd| {
+            self.current_foreign_class = fcd;
+        }
+
+        var reentry = FnBodyReentry.enter(self);
+        defer reentry.restore();
+
+        const ret_ty = self.resolveReturnType(fd);
+
+        // Re-use the existing function slot — switch builder to it.
+        self.builder.func = fid;
+        const func = &self.module.functions.items[@intFromEnum(fid)];
+        self.setCurrentSourceFile(func.source_file);
+        if (!func.is_extern) {
+            // Already promoted (e.g., via lowerComptimeDeps) — skip.
+            return;
+        }
+        func.is_extern = false; // promote from extern stub to real function
+        func.linkage = if (isExportedEntryName(name)) .external else .internal;
+        if (fd.call_conv == .c) func.call_conv = .c;
+        // Set inst_counter to param count (params occupy refs 0..N-1). IR params
+        // = AST params + 1 if the function carries `__sx_ctx` at slot 0.
+        const ctx_slots: usize = if (func.has_implicit_ctx) 1 else 0;
+        std.debug.assert(func.params.len == fd.params.len + ctx_slots);
+        self.builder.inst_counter = @intCast(func.params.len);
+
+        // Create entry block
+        const entry_name = self.module.types.internString("entry");
+        const entry = self.builder.appendBlock(entry_name, &.{});
+        self.builder.switchToBlock(entry);
+
+        // Create scope and bind params
+        var scope = Scope.init(self.alloc, null);
+        defer scope.deinit();
+        self.scope = &scope;
+
+        // The implicit `__sx_ctx` param (when present) lives at slot 0; user
+        // params shift by one. `current_ctx_ref` is bound to slot 0 so call-site
+        // lowering can prepend it to every sx-to-sx call. For OS-called entry
+        // points (main / JNI hooks) there's no ctx param — synthesise
+        // `&__sx_default_context` and bind `current_ctx_ref` to its address.
+        const wants_ctx = self.funcWantsImplicitCtx(fd);
+        const saved_ctx_ref = self.current_ctx_ref;
+        defer self.current_ctx_ref = saved_ctx_ref;
+        const user_param_base: u32 = if (wants_ctx) 1 else 0;
+        if (wants_ctx) self.current_ctx_ref = Ref.fromIndex(0);
+
+        for (fd.params, 0..) |p, i| {
+            const pty = self.resolveParamType(&p);
+            const slot = self.builder.alloca(pty);
+            const param_ref = Ref.fromIndex(@intCast(i + user_param_base));
+            self.builder.store(slot, param_ref);
+            scope.put(p.name, .{ .ref = slot, .ty = pty, .is_alloca = true });
+        }
+
+        // Inbound entry points + callconv(.c) sx functions: bind current_ctx_ref
+        // to the static default before any user code runs.
+        if (!wants_ctx and self.implicit_ctx_enabled) {
+            if (self.program_index.global_names.get("__sx_default_context")) |dctx_gi| {
+                self.current_ctx_ref = self.builder.emit(.{ .global_addr = dctx_gi.id }, self.module.types.ptrTo(.void));
+            }
+        }
+
+        // Lower the function body (set target_type to return type for implicit returns)
+        const saved_target = self.target_type;
+        self.target_type = if (ret_ty != .void and ret_ty != .noreturn) ret_ty else null;
+        if (ret_ty != .void and ret_ty != .noreturn) {
+            self.lowerValueBody(fd.body, ret_ty);
+        } else {
+            // void / noreturn: no value to return — lower as statements and let
+            // `ensureTerminator` close the block (ret void / unreachable).
+            self.lowerBlock(fd.body);
+            self.ensureTerminator(ret_ty);
+        }
+        self.target_type = saved_target;
+
+        self.builder.finalize();
     }
 
     /// Lower a single function declaration.
@@ -3022,10 +3250,36 @@ pub const Lowering = struct {
                         const str = self.builder.constString(sid);
                         break :blk self.builder.boxAny(str, .string);
                     }
-                    if (!self.lowered_functions.contains(eff_fn_name)) {
-                        self.lazyLowerFunction(eff_fn_name);
-                    }
-                    if (self.resolveFuncByName(eff_fn_name)) |fid| {
+                    // fix-0102d site 2: taking a bare same-name fn as a VALUE
+                    // (func_ref, fn-ptr / closure coercion) must capture the
+                    // RESOLVED author's FuncId for a genuine flat collision, not
+                    // the first-wins winner's. Plain bare name only; `.ambiguous`
+                    // → loud diagnostic; `.none` → existing first-wins path. The
+                    // winner is lazily lowered ONLY on `.none` — a rerouted value
+                    // never uses the winner, so its body must not be lowered.
+                    const value_fid: ?FuncId = blk_fv: {
+                        if (std.mem.eql(u8, eff_fn_name, id.name) and
+                            self.program_index.ufcs_alias_map.get(id.name) == null and
+                            (if (self.scope) |scope| scope.lookup(id.name) == null else true))
+                        {
+                            if (self.current_source_file) |caller_file| {
+                                switch (self.resolveBareCallee(id.name, caller_file)) {
+                                    .func => |resolved| break :blk_fv resolved.fid,
+                                    .ambiguous => {
+                                        if (self.diagnostics) |d|
+                                            d.addFmt(.err, node.span, "'{s}' is ambiguous; declared by multiple imported modules — qualify the call", .{id.name});
+                                        break :blk self.emitError(id.name, node.span);
+                                    },
+                                    .none => {},
+                                }
+                            }
+                        }
+                        if (!self.lowered_functions.contains(eff_fn_name)) {
+                            self.lazyLowerFunction(eff_fn_name);
+                        }
+                        break :blk_fv self.resolveFuncByName(eff_fn_name);
+                    };
+                    if (value_fid) |fid| {
                         // Auto-promote bare function → closure when target_type is closure
                         if (self.target_type) |tt| {
                             if (!tt.isBuiltin()) {
@@ -7052,10 +7306,32 @@ pub const Lowering = struct {
                 // If argument is a bare function name, create a proper closure from it
                 if (arg.data == .identifier) {
                     const fn_name = arg.data.identifier.name;
-                    if (!self.lowered_functions.contains(fn_name)) {
-                        self.lazyLowerFunction(fn_name);
-                    }
-                    if (self.resolveFuncByName(fn_name)) |fid| {
+                    // fix-0102d site 2: `closure(fn)` over a genuine flat same-name
+                    // collision must capture the RESOLVED author's FuncId, not the
+                    // first-wins winner's. Plain bare name only; `.ambiguous`
+                    // → loud diagnostic; `.none` → existing first-wins path.
+                    const closure_fid: ?FuncId = blk_cl: {
+                        if (self.program_index.ufcs_alias_map.get(fn_name) == null and
+                            (if (self.scope) |scope| scope.lookup(fn_name) == null else true))
+                        {
+                            if (self.current_source_file) |caller_file| {
+                                switch (self.resolveBareCallee(fn_name, caller_file)) {
+                                    .func => |resolved| break :blk_cl resolved.fid,
+                                    .ambiguous => {
+                                        if (self.diagnostics) |d|
+                                            d.addFmt(.err, arg.span, "'{s}' is ambiguous; declared by multiple imported modules — qualify the call", .{fn_name});
+                                        return Ref.none;
+                                    },
+                                    .none => {},
+                                }
+                            }
+                        }
+                        if (!self.lowered_functions.contains(fn_name)) {
+                            self.lazyLowerFunction(fn_name);
+                        }
+                        break :blk_cl self.resolveFuncByName(fn_name);
+                    };
+                    if (closure_fid) |fid| {
                         const func = &self.module.functions.items[@intFromEnum(fid)];
                         // Build closure type from user-visible params only —
                         // skip the implicit __sx_ctx param.
@@ -7338,6 +7614,41 @@ pub const Lowering = struct {
                         }
                     }
                 }
+                // fix-0102c: a genuine flat same-name collision — bind the
+                // caller file's OWN author (or its single flat-reachable
+                // author), or reject a bare call to a name ≥2 imported modules
+                // author. Only a plain top-level identifier call routes here:
+                // scope-mangled / UFCS-aliased / locally-shadowed names and
+                // 0/1-author names fall straight to the existing path below
+                // (`resolveBareCallee` returns `.none`).
+                if (std.mem.eql(u8, func_name, id.name) and
+                    (if (self.scope) |scope| scope.lookup(id.name) == null else true))
+                {
+                    if (self.current_source_file) |caller_file| {
+                        switch (self.resolveBareCallee(func_name, caller_file)) {
+                            .none => {},
+                            .ambiguous => {
+                                if (self.diagnostics) |d|
+                                    d.addFmt(.err, c.callee.span, "'{s}' is ambiguous; declared by multiple imported modules — qualify the call", .{func_name});
+                                return Ref.none;
+                            },
+                            .func => |resolved| {
+                                const fid = resolved.fid;
+                                const func = &self.module.functions.items[@intFromEnum(fid)];
+                                const ret_ty = func.ret;
+                                const params = func.params;
+                                // The RESOLVED author's decl drives variadic
+                                // packing — not a first-wins re-lookup by name,
+                                // whose variadic shape may differ (fix-0102c F1).
+                                self.packVariadicCallArgs(resolved.decl, c, &args);
+                                const final_args = self.prependCtxIfNeeded(func, args.items);
+                                self.coerceCallArgs(final_args, params);
+                                if (func.is_variadic) self.promoteCVariadicArgs(final_args, params.len);
+                                return self.builder.call(fid, final_args, ret_ty);
+                            },
+                        }
+                    }
+                }
                 // Check for comptime-expanded or generic functions
                 if (self.program_index.fn_ast_map.get(func_name)) |fd| {
                     if (hasComptimeParams(fd)) {
@@ -7820,12 +8131,33 @@ pub const Lowering = struct {
                 // `recv.fn(args)` → `fn(recv, args)`). Lazily lower the body —
                 // a function reached ONLY via UFCS would otherwise be declared
                 // but never emitted (issue 0063: undefined symbol at link).
-                if (self.program_index.fn_ast_map.get(fa.field)) |_| {
-                    if (!self.lowered_functions.contains(fa.field)) {
-                        self.lazyLowerFunction(fa.field);
+                //
+                // fix-0102d site 3: a free-function UFCS target with a genuine
+                // flat same-name collision must dispatch to the RESOLVED author
+                // for the receiver's source, not the first-wins winner. The
+                // field name is never scope-mangled, so the only gate is a
+                // known source file; `.ambiguous` → loud diagnostic; `.none`
+                // → existing first-wins path.
+                const ufcs_fid: ?FuncId = blk_uf: {
+                    if (self.current_source_file) |caller_file| {
+                        switch (self.resolveBareCallee(fa.field, caller_file)) {
+                            .func => |resolved| break :blk_uf resolved.fid,
+                            .ambiguous => {
+                                if (self.diagnostics) |d|
+                                    d.addFmt(.err, c.callee.span, "'{s}' is ambiguous; declared by multiple imported modules — qualify the call", .{fa.field});
+                                return Ref.none;
+                            },
+                            .none => {},
+                        }
                     }
-                }
-                if (self.resolveFuncByName(fa.field)) |fid| {
+                    if (self.program_index.fn_ast_map.get(fa.field)) |_| {
+                        if (!self.lowered_functions.contains(fa.field)) {
+                            self.lazyLowerFunction(fa.field);
+                        }
+                    }
+                    break :blk_uf self.resolveFuncByName(fa.field);
+                };
+                if (ufcs_fid) |fid| {
                     const func = &self.module.functions.items[@intFromEnum(fid)];
                     const ret_ty = func.ret;
                     const params = func.params;
@@ -11611,6 +11943,24 @@ pub const Lowering = struct {
                         }
                         break :blk2 scoped;
                     };
+                    // fix-0102d site 1: for a genuine flat same-name collision the
+                    // omitted trailing args must be filled from the RESOLVED
+                    // author's defaults, not the first-wins winner's. Only a plain
+                    // top-level identifier with no scope-mangle / UFCS alias /
+                    // local shadow routes here; `.ambiguous` declines to expand
+                    // (the call path emits the single diagnostic); `.none` keeps
+                    // the existing first-wins winner, byte-for-byte.
+                    if (std.mem.eql(u8, eff_name, id.name) and
+                        (if (self.scope) |scope| scope.lookup(id.name) == null else true))
+                    {
+                        if (self.current_source_file) |caller_file| {
+                            switch (self.resolveBareCallee(id.name, caller_file)) {
+                                .func => |resolved| break :blk resolved.decl,
+                                .ambiguous => return null,
+                                .none => {},
+                            }
+                        }
+                    }
                     break :blk self.program_index.fn_ast_map.get(eff_name) orelse return null;
                 },
                 // Namespace call `mod.fn(args)` — args map directly to params
@@ -11833,6 +12183,29 @@ pub const Lowering = struct {
             break :blk scoped;
         };
 
+        // fix-0102c F2: a genuine flat same-name collision must type this
+        // call's args against the RESOLVED author's params, not the first-wins
+        // winner's. Mirror the `lowerCall` routing one layer earlier so arg
+        // lowering (implicit address-of, coercion) matches the author actually
+        // called — otherwise a `*T`-param shadow gets a `T` value arg that is
+        // later bit-cast to a pointer (segfault). Only a plain top-level
+        // identifier with no scope-mangle / UFCS alias / local shadow routes
+        // here; `.ambiguous` / `.none` fall to the existing first-wins path so
+        // single-author / local / std resolution is byte-for-byte unchanged.
+        if (std.mem.eql(u8, name, bare_name) and
+            (if (self.scope) |scope| scope.lookup(bare_name) == null else true))
+        {
+            if (self.current_source_file) |caller_file| {
+                switch (self.resolveBareCallee(bare_name, caller_file)) {
+                    .func => |resolved| {
+                        const func = &self.module.functions.items[@intFromEnum(resolved.fid)];
+                        return self.userParamTypes(func);
+                    },
+                    .ambiguous, .none => {},
+                }
+            }
+        }
+
         // Check declared functions
         if (self.resolveFuncByName(name)) |fid| {
             const func = &self.module.functions.items[@intFromEnum(fid)];
@@ -11890,6 +12263,19 @@ pub const Lowering = struct {
         return false;
     }
 
+    /// A plain free function: no type params (not generic) and an ordinary sx
+    /// body (not `#foreign` / `#builtin` / `#compiler`). Only these get an
+    /// out-of-line identity-addressable slot — the bare-call disambiguation
+    /// (fix-0102c) and the shadow-author lowering pass leave every other shape
+    /// to the existing name-keyed dispatch.
+    fn isPlainFreeFn(fd: *const ast.FnDecl) bool {
+        if (fd.type_params.len > 0) return false;
+        return switch (fd.body.data) {
+            .foreign_expr, .builtin_expr, .compiler_expr => false,
+            else => true,
+        };
+    }
+
     /// Pack-fn: has a trailing heterogeneous pack param (`is_variadic
     /// AND is_comptime`). Mixed shapes — non-pack comptime params
     /// before the pack — are also accepted; the mono folds those

src/ir/program_index.zig

@@ -1,5 +1,6 @@
 const std = @import("std");
 const ast = @import("../ast.zig");
+const imports = @import("../imports.zig");
 const types = @import("types.zig");
 const inst = @import("inst.zig");
 const errors = @import("../errors.zig");
@@ -570,9 +571,10 @@ pub const GlobalInfo = struct { id: inst.GlobalId, ty: TypeId };
 /// `self.program_index.<field>`; later phases hand collaborator modules a
 /// `*ProgramIndex` instead of `*Lowering`.
 ///
-/// OWNS the declaration maps below. BORROWS `module_scopes` / `import_graph`
-/// (pointers into maps owned by the compilation driver, `core.zig`) — those
-/// are read-only views and are never freed here.
+/// OWNS the declaration maps below. BORROWS `module_scopes` / `import_graph` /
+/// `flat_import_graph` / `module_fns` (pointers into maps owned by the
+/// compilation driver, `core.zig`) — those are read-only views and are never
+/// freed here.
 ///
 /// Per-map allocators are preserved exactly as they were on `Lowering`:
 /// `import_flags` / `fn_ast_map` / `global_names` use the lowering allocator
@@ -587,6 +589,16 @@ pub const ProgramIndex = struct {
     /// Module path → set of directly imported paths (param_impl visibility
     /// filter). Borrowed view.
     import_graph: ?*std.StringHashMap(std.StringHashMap(void)) = null,
+    /// Module path → set of directly FLAT-imported paths — the subset of
+    /// `import_graph` edges from a bare `#import` (never a namespaced
+    /// `ns :: #import`). fix-0102c's bare-name disambiguation walks this to
+    /// decide which same-name authors a flat importer can reach. Borrowed view.
+    flat_import_graph: ?*std.StringHashMap(std.StringHashMap(void)) = null,
+    /// Module path → (function name → authoring `*const FnDecl`), mirroring
+    /// `module_scopes`. Retains every same-name author under its own path so
+    /// fix-0102c can resolve a flat call to the right module's function.
+    /// Borrowed view.
+    module_fns: ?*imports.ModuleFns = null,
 
     // ── Declaration maps ──
     /// Function name → AST decl.
@@ -627,7 +639,8 @@ pub const ProgramIndex = struct {
     }
 
     pub fn deinit(self: *ProgramIndex) void {
-        // Owned maps only — module_scopes / import_graph are borrowed.
+        // Owned maps only — module_scopes / import_graph / flat_import_graph /
+        // module_fns are borrowed.
         self.import_flags.deinit();
         self.fn_ast_map.deinit();
         self.qualified_fn_source.deinit();

src/root.zig

@@ -13,6 +13,7 @@ pub const trace_runtime_tests = @import("runtime_trace.test.zig");
 pub const sema = @import("sema.zig");
 pub const sema_tests = @import("sema.test.zig");
 pub const imports = @import("imports.zig");
+pub const imports_tests = @import("imports.test.zig");
 pub const core = @import("core.zig");
 pub const c_import = @import("c_import.zig");
 pub const ir = @import("ir/ir.zig");