lang: fn aliases dispatch like their target (fix 0121) — scan-time registration through the shared alias-chain walk

Renamed fn aliases failed for EVERY kind (the filed pack-only scope was a same-name confound: same-name re-exports already resolved through the name-keyed fn_ast_map). scanDecls now follows ident-/ns.X-RHS const alias chains (aliasedFnDecl; 0120's hop walk extracted as followAliasChain) and registers the alias name in fn_ast_map (absent-only), so every dispatch path — early pack/comptime/generic, plain lazy-lower, plan-side typing — sees the target decl unchanged. my_print :: s.print; / my_format :: s.format; now work (the std.sx re-export shape). Regression: examples/0546 (+rich). Gates: zig build test 0, suite 588/588.
2026-06-11 18:47:16 +03:00
parent f2db8ecc53
commit 721369a711
11 changed files with 264 additions and 53 deletions
--- a/examples/0546-packs-fn-alias-rich.sx
+++ b/examples/0546-packs-fn-alias-rich.sx
@@ -0,0 +1,6 @@
+// Companion of 0546: the authoring module for the fn-alias re-exports.
+#import "modules/std.sx";
+
+helper :: () -> s64 { 7 }
+first_of :: (xs: []$T) -> T { xs[0] }
+my_pack :: (..$args) -> s64 { args[0] + args[1] }
--- a/examples/0546-packs-fn-alias.sx
+++ b/examples/0546-packs-fn-alias.sx
@@ -0,0 +1,35 @@
+// Function aliases dispatch exactly like their target, across every fn
+// kind: plain, runtime-generic ([]$T), and comptime-pack (..$args) — with
+// bare, renamed, and namespace-member RHS. The alias is an ordinary own
+// declaration, so it re-exports one flat-import level (companion file
+// -rich.sx authors the fns aliased here and via the namespace).
+// Regression (issue 0121): comptime-pack fn aliases (and ALL renamed fn
+// aliases) used to fail "unresolved '<alias>'" — only same-name re-exports
+// worked, through the name-keyed global registry.
+#import "modules/std.sx";
+s :: #import "modules/std.sx";
+r :: #import "0546-packs-fn-alias-rich.sx";
+
+pack_sum :: (..$args) -> s64 {
+    args[0] + args[1]
+}
+sum_alias :: pack_sum;        // same-file pack alias (the 0121 repro)
+
+helper2 :: r.helper;          // renamed plain, namespace RHS
+head_of :: r.first_of;        // renamed runtime-generic, namespace RHS
+sum2 :: r.my_pack;            // renamed pack, namespace RHS
+
+my_print :: s.print;          // std's print — comptime pack + $fmt
+my_format :: s.format;        // value-returning sibling
+
+main :: () {
+    print("pack: {}\n", sum_alias(3, 4));
+    print("plain: {}\n", helper2());
+    arr := .[10, 20, 30];
+    xs : []s64 = arr;
+    print("generic: {}\n", head_of(xs));
+    print("ns-pack: {}\n", sum2(20, 22));
+    my_print("std-print: {} {}\n", 1, "two");
+    t := my_format("std-format {}", 42);
+    my_print("{}\n", t);
+}
--- a/examples/expected/0546-packs-fn-alias.exit
+++ b/examples/expected/0546-packs-fn-alias.exit
@@ -0,0 +1 @@
+0
--- a/examples/expected/0546-packs-fn-alias.stderr
+++ b/examples/expected/0546-packs-fn-alias.stderr
@@ -0,0 +1 @@
+
--- a/examples/expected/0546-packs-fn-alias.stdout
+++ b/examples/expected/0546-packs-fn-alias.stdout
@@ -0,0 +1,6 @@
+pack: 7
+plain: 7
+generic: 10
+ns-pack: 42
+std-print: 1 two
+std-format 42
--- a/issues/0121-pack-fn-alias-unresolved.md
+++ b/issues/0121-pack-fn-alias-unresolved.md
@@ -0,0 +1,112 @@
+# 0121 — aliasing a comptime-pack fn (`..$args`): "unresolved '<alias>'"
+
+> **RESOLVED** (2026-06-11, same session — Agra-directed). The symptom
+> was broader than filed: RENAMED fn aliases failed for EVERY fn kind
+> (plain `helper2 :: r.helper;` too) — the "plain fns verified working"
+> claim below was a same-name confound (same-name re-exports resolve
+> through the name-keyed global `fn_ast_map`, no alias mechanism
+> involved; `my_pack :: r.my_pack;` already worked for packs too).
+> Fix: fn aliases register at SCAN time — `scanDecls`' const-decl arm
+> follows ident-/`ns.X`-RHS alias chains via `aliasedFnDecl`
+> (nominal.zig; shares 0120's hop walk, now extracted as
+> `followAliasChain`) and, when the chain terminates at a fn decl,
+> registers the ALIAS name in `fn_ast_map` (absent-only — a real
+> same-name fn keeps its slot). Every dispatch path reads that map
+> (early pack/comptime/generic, plain lazy-lower, plan-side typing),
+> so the alias dispatches exactly like the target with no per-path
+> changes. Verified matrix: same-file pack alias (the repro), renamed
+> plain / generic / pack through a facade, and `my_print :: s.print;`
+> / `my_format :: s.format;` over std's real pack fns. Regression:
+> `examples/0546-packs-fn-alias.sx` (+ `-rich.sx` companion). Gates:
+> zig build test 0, suite 588/588.
+
+## Symptom
+
+A const alias of a function whose signature carries a comptime pack
+(`..$args`) is not callable — every call through the alias fails with
+`unresolved '<alias>'`. All three alias shapes fail identically:
+
+- same-file bare: `sum_alias :: pack_sum;` → `unresolved 'sum_alias'`
+- bare RHS over a flat import: `my_print :: print;` (std's `print`) →
+  `unresolved 'my_print'`
+- namespace RHS: `my_print :: s.print;` with `s :: #import
+  "modules/std.sx";` → `unresolved 'my_print'`
+
+Contrast (all verified working): plain concrete fns (`helper ::
+r.helper;`), runtime-generic fns (`first_of :: r.first_of;` with
+`(xs: []$T) -> T`), and — since 0120 — generic struct heads
+(`List :: list.List;`). Only the comptime-pack shape misses.
+
+Expected: the alias dispatches exactly like the target —
+`my_print("x {}\n", 1)` behaves as `print("x {}\n", 1)`. (If fn
+aliasing of pack fns is NOT meant to be promised, the hypothesis is
+wrong and the decl or the call should get a clean tailored
+diagnostic instead — but the std.sx-as-pure-re-exports restructure
+wants `print :: fmt.print;` to work, so support is the desirable
+outcome. Confirm with Agra only if support turns out prohibitively
+deep.)
+
+## Reproduction
+
+```sx
+#import "modules/std.sx";
+
+pack_sum :: (..$args) -> s64 {
+    args[0] + args[1]
+}
+sum_alias :: pack_sum;
+
+main :: () {
+    print("{}\n", sum_alias(3, 4));   // error: unresolved 'sum_alias'
+}
+```
+
+Direct `pack_sum(3, 4)` works; only the aliased spelling fails.
+
+## Investigation prompt
+
+Comptime-pack calls (`..$args` — NOT slice-variadics `..xs: []T`)
+dispatch EARLY in call lowering, keyed on the callee NAME against the
+pack-fn template registry (the `fn_ast_map` entry whose FnDecl has a
+comptime pack param; the early-dispatch gate lives in the call path —
+`src/ir/lower/call.zig` / `src/ir/packs.zig`, grep for the pack-param
+detection on the callee). An alias name has no `fn_ast_map` entry, so
+the early pack dispatch misses; no later stage handles pack fns
+(they cannot lower as ordinary declared functions — each call site
+expands with its own bound pack), so the call falls through to the
+generic `unresolved '<name>'`.
+
+The fix likely: where the early pack dispatch resolves the callee
+name, on a miss follow const-ALIAS decls to their target FnDecl and
+dispatch with the TARGET's fd under the alias's call node. Issue
+0120's fix added exactly this follow for generic STRUCT heads —
+`aliasedStructTemplate` in `src/ir/lower/nominal.zig`
+(`singleVisibleAuthor` + hop-by-hop `followToTemplate`, each hop
+resolved from the ALIAS AUTHOR's source, `namespaceAliasVerdictFrom`
+for `ns.X` RHS, depth-capped). Mirror that shape for fn targets — a
+`followToFnDecl` sibling reusing `singleVisibleAuthor` (consider
+extracting the shared walk) — and route the early pack dispatch
+through it. Mind: own-wins / single-flat collision semantics must
+match 0120's (≥2 flat alias authors → loud, no silent pick), and the
+ufcs-alias map (`name :: ufcs target;`) is a DIFFERENT mechanism
+(`ufcs_alias_map`) — don't conflate.
+
+Verification:
+
+1. The repro prints `7`, exit 0.
+2. Matrix: same-file bare alias, bare RHS over a flat import
+   (`my_print :: print;`), namespace RHS (`my_print :: s.print;` /
+   `my_format :: s.format;` — formats AND returns a value), and a
+   consumer one flat hop from the aliasing facade.
+3. Plain-fn and generic-fn aliases unchanged (examples 0211 family).
+4. `bash tests/run_examples.sh` — 587/587 baseline must hold; pin the
+   repro as a regression example per CLAUDE.md.
+
+Context: BLOCKS the std.sx-as-pure-re-exports restructure — `print` /
+`format` are the prelude's most-used names and are exactly this shape
+(`($fmt: string, ..$args)`). Generic struct heads (`List`) were
+unblocked by 0120; this is the remaining known gap. Still unprobed
+for the restructure (next session, after this fix): protocol aliases
+(`Allocator`, parameterized `Into`), `#builtin` decl aliases
+(`size_of`, `out`, `string :: []u8`), `#foreign` decl aliases
+(`memcpy`).
--- a/readme.md
+++ b/readme.md
@@ -486,9 +486,10 @@ carry does not chain through a second flat hop.
 **Re-exporting through alias declarations.** Since visibility never chains,
 a facade re-exports another module's members as its OWN declarations —
 ordinary aliases, which its direct flat importers then see bare. This works
-for functions, plain types, and generic struct heads alike (the generic
-alias binds the same template, so instantiation and methods resolve
-through it):
+for functions of every kind (plain, generic, comptime-pack like `print`),
+plain types, and generic struct heads alike (the generic alias binds the
+same template, so instantiation and methods resolve through it), renamed
+or same-name:

 ```sx
 // facade.sx
--- a/specs.md
+++ b/specs.md
@@ -1270,6 +1270,23 @@ chain resolves with the visibility of the file that declares THAT hop,
 not the use site's. Not yet supported: a qualified head whose namespace
 member is itself an alias (`ns.BoxAlias(..)`).

+### Function Aliases
+
+Functions alias the same way — bare or namespace-member RHS, renamed or
+same-name — and the alias dispatches exactly like the target. This covers
+every fn kind: plain, runtime-generic (`[]$T` / `$T: Type`), and
+comptime-pack (`..$args`, e.g. `print` / `format`):
+
+```sx
+s :: #import "modules/std.sx";
+my_print :: s.print;          // comptime-pack fn through a namespace
+helper2  :: r.helper;         // renamed plain fn
+my_print("x = {}\n", helper2());
+```
+
+(For making an alias *dot-callable*, see `name :: ufcs target;` in the
+UFCS section — that is a separate, explicit opt-in.)
+
 ### Generic Functions (Monomorphization)
 Functions can be parameterized over types using `$T` syntax. The `$` prefix introduces a type parameter; subsequent uses of the name reference it.
 ```sx
--- a/src/ir/lower.zig
+++ b/src/ir/lower.zig
@@ -1688,6 +1688,7 @@ pub const Lowering = struct {
    pub const buildGenericStructTemplate = lower_nominal.buildGenericStructTemplate;
    pub const qualifiedStructTemplate = lower_nominal.qualifiedStructTemplate;
    pub const aliasedStructTemplate = lower_nominal.aliasedStructTemplate;
+    pub const aliasedFnDecl = lower_nominal.aliasedFnDecl;
    pub const qualifiedMemberMissing = lower_nominal.qualifiedMemberMissing;
    pub const bareVisibleStructDecl = lower_nominal.bareVisibleStructDecl;
    pub const bareVisibleStructTemplate = lower_nominal.bareVisibleStructTemplate;
--- a/src/ir/lower/decl.zig
+++ b/src/ir/lower/decl.zig
@@ -211,8 +211,7 @@ pub fn checkRequiredEntryPoints(self: *Lowering) void {
    }

    if (self.diagnostics) |diags| {
-        diags.addFmt(.err, null,
-            "target is Android but no `#jni_main` Activity declared. " ++
+        diags.addFmt(.err, null, "target is Android but no `#jni_main` Activity declared. " ++
            "The OS launches a Java-side Activity that delegates lifecycle " ++
            "callbacks into sx — declare one like:\n\n" ++
            "    Bundle :: #foreign #jni_class(\"android/os/Bundle\") {{ }}\n\n" ++
@@ -366,8 +365,7 @@ pub fn detectContextDecl(decls: []const *const Node) bool {
    for (decls) |decl| {
        const found = switch (decl.data) {
            .struct_decl => |sd| std.mem.eql(u8, sd.name, "Context"),
-            .const_decl => |cd|
-                std.mem.eql(u8, cd.name, "Context") and cd.value.data == .struct_decl,
+            .const_decl => |cd| std.mem.eql(u8, cd.name, "Context") and cd.value.data == .struct_decl,
            .namespace_decl => |ns| detectContextDecl(ns.decls),
            else => false,
        };
@@ -596,30 +594,48 @@ pub fn scanDecls(self: *Lowering, decls: []const *const Node) void {
                        }
                    }
                    self.putTypeAlias(self.current_source_file, cd.name, target_ty);
-                } else if (cd.value.data == .identifier) {
-                    // Identifier-RHS alias: MyAlias :: MyInt;  WideAlias :: Wide.
-                    // SOURCE-AWARE (E1.5). Resolve the RHS `B` AS SEEN FROM this
-                    // alias's OWN source via `selectNominalLeaf` (E1's source-
-                    // keyed nominal leaf), NEVER the global `type_alias_map` /
-                    // global `findByName` (last-wins across modules). Only the
-                    // `.resolved` outcome is written; `.pending` (B is itself a
-                    // forward alias not resolved yet), `.undeclared`, and
-                    // `.not_visible` (a same-name B authored only by a namespaced
-                    // import) leave A UNWRITTEN so the source-aware
-                    // `resolveForwardIdentifierAliases` fixpoint re-tries A once
-                    // the local B registers. A GLOBAL selection here would bind A
-                    // to a namespaced same-name B, and the per-source fixpoint
-                    // guard (`aliasResolvedInSource`) would then SKIP A — leaving
-                    // the wrong global TypeId and re-opening 0105 one layer down
-                    // (R1, E1.5). Same unified `putTypeAlias` writer (no-drift).
-                    const rhs = cd.value.data.identifier;
+                } else if (cd.value.data == .identifier or cd.value.data == .field_access) {
+                    // FN alias (issue 0121): `print2 :: print;` /
+                    // `my_print :: s.print;`. When the alias chain terminates
+                    // at a fn decl, register the ALIAS name in `fn_ast_map`
+                    // pointing at the target's decl — every dispatch path
+                    // (early pack/comptime/generic, plain lazy-lower,
+                    // plan-side return typing) reads that map, so the alias
+                    // dispatches exactly like the target. Absent-only: a real
+                    // same-name fn keeps its slot (same-name re-exports are
+                    // a no-op — the target already owns the name).
                    if (self.current_source_file orelse self.main_file) |from| {
-                        switch (self.selectNominalLeaf(rhs.name, from, rhs.is_raw)) {
-                            .resolved => |tid| self.putTypeAlias(self.current_source_file, cd.name, tid),
-                            // `.ambiguous` (same-name RHS authored by ≥2 flat
-                            // imports) leaves A unwritten like `.not_visible`;
-                            // the loud diagnostic fires where A is USED.
-                            .pending, .forward, .undeclared, .not_visible, .ambiguous => {},
+                        if (self.aliasedFnDecl(&decl.data.const_decl, from)) |target_fd| {
+                            if (!self.program_index.fn_ast_map.contains(cd.name)) {
+                                self.program_index.fn_ast_map.put(cd.name, target_fd) catch {};
+                            }
+                        }
+                    }
+                    if (cd.value.data == .identifier) {
+                        // Identifier-RHS alias: MyAlias :: MyInt;  WideAlias :: Wide.
+                        // SOURCE-AWARE (E1.5). Resolve the RHS `B` AS SEEN FROM this
+                        // alias's OWN source via `selectNominalLeaf` (E1's source-
+                        // keyed nominal leaf), NEVER the global `type_alias_map` /
+                        // global `findByName` (last-wins across modules). Only the
+                        // `.resolved` outcome is written; `.pending` (B is itself a
+                        // forward alias not resolved yet), `.undeclared`, and
+                        // `.not_visible` (a same-name B authored only by a namespaced
+                        // import) leave A UNWRITTEN so the source-aware
+                        // `resolveForwardIdentifierAliases` fixpoint re-tries A once
+                        // the local B registers. A GLOBAL selection here would bind A
+                        // to a namespaced same-name B, and the per-source fixpoint
+                        // guard (`aliasResolvedInSource`) would then SKIP A — leaving
+                        // the wrong global TypeId and re-opening 0105 one layer down
+                        // (R1, E1.5). Same unified `putTypeAlias` writer (no-drift).
+                        const rhs = cd.value.data.identifier;
+                        if (self.current_source_file orelse self.main_file) |from| {
+                            switch (self.selectNominalLeaf(rhs.name, from, rhs.is_raw)) {
+                                .resolved => |tid| self.putTypeAlias(self.current_source_file, cd.name, tid),
+                                // `.ambiguous` (same-name RHS authored by ≥2 flat
+                                // imports) leaves A unwritten like `.not_visible`;
+                                // the loud diagnostic fires where A is USED.
+                                .pending, .forward, .undeclared, .not_visible, .ambiguous => {},
+                            }
                        }
                    }
                }
@@ -686,7 +702,7 @@ pub fn scanDecls(self: *Lowering, decls: []const *const Node) void {
                    // template via the namespace edge (mirrors the annotation
                    // head site `resolveParameterizedWithBindings`), not the
                    // bare last-wins `struct_template_map`.
-                    const pt_alias: ?[]const u8 = if (pt_qualified) pt.name[0 .. std.mem.indexOfScalar(u8, pt.name, '.').?] else null;
+                    const pt_alias: ?[]const u8 = if (pt_qualified) pt.name[0..std.mem.indexOfScalar(u8, pt.name, '.').?] else null;
                    // Generic-struct alias base: route layout selection through the
                    // single choke-point (CP-1); the builtin parameterised-type
                    // path (Vector etc.) stays as the non-generic fall-through.
@@ -1669,7 +1685,9 @@ pub fn selectNominalLeaf(self: *Lowering, name: []const u8, from: []const u8, ra
            else => self.namedRefTid(fa.raw, name),
        };
        if (fa_tid) |t| {
-            if (found_tid) |f| { if (t != f) return .ambiguous; } else found_tid = t;
+            if (found_tid) |f| {
+                if (t != f) return .ambiguous;
+            } else found_tid = t;
        } else {
            flat_has_unregistered = true;
        }
--- a/src/ir/lower/nominal.zig
+++ b/src/ir/lower/nominal.zig
@@ -434,35 +434,48 @@ pub fn aliasedStructTemplate(self: *Lowering, name: []const u8, from: []const u8
 }

 /// One alias hop: a generic-struct author terminates the chain with its
-/// rebuilt source-pinned template; an alias author recurses on its RHS —
-/// bare identifier from the author's own source, `ns.X` through the
-/// author's namespace edge into the target module's own member. The depth
-/// cap breaks alias cycles (`A :: B; B :: A;`).
+/// rebuilt source-pinned template; an alias author recurses via
+/// `followAliasChain`.
 fn followToTemplate(self: *Lowering, author: resolver_mod.RawAuthor, depth: u8) ?StructTemplate {
+    const terminal = followAliasChain(self, author, depth) orelse return null;
+    const sd = structDeclOfRaw(terminal.raw) orelse return null;
+    if (sd.type_params.len == 0) return null;
+    return self.buildGenericStructTemplate(sd, terminal.source);
+}
+
+/// Walk a chain of const ALIAS decls to its terminal author. Each hop
+/// resolves the RHS from the hop AUTHOR's own source — a bare identifier
+/// via the visible-author walk, `ns.X` through the author's namespace edge
+/// into the target module's own member. A non-alias author terminates the
+/// chain (callers unwrap it by domain: `structDeclOfRaw` / `fnDeclOfRaw`).
+/// The depth cap breaks alias cycles (`A :: B; B :: A;`).
+pub fn followAliasChain(self: *Lowering, author: resolver_mod.RawAuthor, depth: u8) ?resolver_mod.RawAuthor {
    if (depth == 0) return null;
-    if (structDeclOfRaw(author.raw)) |sd| {
-        if (sd.type_params.len == 0) return null;
-        return self.buildGenericStructTemplate(sd, author.source);
-    }
-    const cd = constAliasOfRaw(author.raw) orelse return null;
-    switch (cd.value.data) {
-        .identifier => |id| {
-            const next = singleVisibleAuthor(self, id.name, author.source) orelse return null;
-            return followToTemplate(self, next, depth - 1);
-        },
-        .field_access => |fa| {
-            if (fa.object.data != .identifier) return null;
+    const cd = constAliasOfRaw(author.raw) orelse return author;
+    const next: ?resolver_mod.RawAuthor = switch (cd.value.data) {
+        .identifier => |id| singleVisibleAuthor(self, id.name, author.source),
+        .field_access => |fa| blk: {
+            if (fa.object.data != .identifier) break :blk null;
            const target = switch (self.namespaceAliasVerdictFrom(fa.object.data.identifier.name, author.source)) {
                .target => |t| t,
-                .none, .ambiguous => return null,
+                .none, .ambiguous => break :blk null,
            };
            var res = self.resolver();
            const member_set = res.collectNamespaceAuthors(target, fa.field);
-            const member = member_set.own orelse return null;
-            return followToTemplate(self, member, depth - 1);
+            break :blk member_set.own;
        },
-        else => return null,
-    }
+        else => null,
+    };
+    return followAliasChain(self, next orelse return null, depth - 1);
+}
+
+/// The fn decl a const ALIAS chain terminates at, or null when `cd` is not
+/// an alias of a function. Entry for fn-alias registration (issue 0121):
+/// `cd` itself seeds the chain (it IS the first alias hop), `from` is its
+/// declaring source.
+pub fn aliasedFnDecl(self: *Lowering, cd: *const ast.ConstDecl, from: []const u8) ?*const ast.FnDecl {
+    const terminal = followAliasChain(self, .{ .raw = .{ .const_decl = cd }, .source = from }, 9) orelse return null;
+    return Lowering.fnDeclOfRaw(terminal.raw);
 }

 /// The bare-VISIBLE single generic-struct author of `name` (its `StructDecl` +