feat(stdlib/S2.1c): foreign-class + struct-const + UFCS — final 3 domains on the owning pass [additive]

On the S2.1a owning traversal, populate the last three ResolvedProgram side
tables, closing planspec S2.1's full-population acceptance (all ten domains):

  - foreign_class_refs: a bare reference whose collected author is a
    foreign_class_decl is routed here (its own domain) instead of the bare
    type/value/callable table.
  - struct_const_refs: a Type.CONST field access whose base resolves to a
    struct author carrying that const member (mirrors lowering's struct_const_map).
  - ufcs_refs: a ufcs_alias decl (alias -> target author) plus its UFCS-rewrite
    call sites (alias(args), incl. pipe-desugared), via a global traversal-ordered
    alias map mirroring lowering's flat ufcs_alias_map.

Still PARALLEL / UNCONSUMED / RAW: lowering reads the OLD selectors, no consumer
cut over, ResolvedRef stays raw. Byte-identical vs baseline (540 examples).

Population proof extended: a new resolver.test fixture exercises all ten domains
at once and asserts each side table non-empty + node-keyed for the three new ones.

src/ir/resolver.test.zig

@@ -703,3 +703,145 @@ test "resolver: resolve — namespace-qualified + generic-struct/type-fn/protoco
     try std.testing.expectEqual(@as(u32, 0), rp.struct_const_refs.count());
     try std.testing.expectEqual(@as(u32, 0), rp.ufcs_refs.count());
 }
+
+// ── the owning resolution pass — S2.1c final three domains + FULL population ──
+
+// S2.1c closes the set on the SAME traversal, still RAW / PARALLEL / UNCONSUMED.
+// (1) A bare reference whose author is a `foreign_class_decl` (`o: Obj`) is routed
+// into foreign_class_refs — NOT type_refs. (2) A `Type.CONST` field access whose
+// base resolves to a struct carrying that const member (`Phys.GRAVITY`) fills
+// struct_const_refs, keyed by the field_access node. (3) A UFCS alias
+// (`plus :: ufcs adder`) is keyed by its decl node AND its rewrite call site
+// (`plus(1, 2)`) is keyed by the callee, both resolving to the target's author.
+// This fixture exercises ALL TEN domains at once, proving the full-population
+// acceptance: every ResolvedProgram side table is non-empty and node-keyed.
+test "resolver: resolve — S2.1c foreign-class/struct-const/UFCS + all ten domains populated" {
+    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 = "lib.sx", .data = "helper :: () -> s64 { 5 }\n" });
+    try tmp.dir.writeFile(io, .{ .sub_path = "ns.sx", .data = "helper_fn :: () -> s64 { 7 }\n" });
+    try tmp.dir.writeFile(io, .{ .sub_path = "main.sx", .data =
+        \\#import "lib.sx";
+        \\g :: #import "ns.sx";
+        \\Obj :: #foreign #objc_class("Obj") {
+        \\    alloc :: () -> *Obj;
+        \\}
+        \\Phys :: struct { mass: s64; GRAVITY :: 10; }
+        \\Box :: struct($T: Type) { value: T }
+        \\Make :: ($T: Type) -> Type { return [3]T; }
+        \\Cmp :: protocol(T: Type) { get :: () -> T; }
+        \\LIMIT :: 5;
+        \\adder :: (a: s64, b: s64) -> s64 { a + b }
+        \\plus :: ufcs adder;
+        \\use_phys :: (p: Phys) -> s64 { p.mass }
+        \\use_obj :: (o: Obj) -> s64 { 0 }
+        \\use_box :: (b: Box(s64)) -> s64 { 0 }
+        \\use_make :: (m: Make(s64)) -> s64 { 0 }
+        \\use_cmp :: (c: Cmp(s64)) -> s64 { 0 }
+        \\read_const :: () -> s64 { Phys.GRAVITY }
+        \\read_ns :: () -> s64 { g.helper_fn() }
+        \\call_alias :: () -> s64 { plus(1, 2) }
+        \\main :: () -> s32 {
+        \\    n := helper();
+        \\    m := LIMIT;
+        \\    _ = n;
+        \\    _ = m;
+        \\    return 0;
+        \\}
+        \\
+    });
+
+    var dirbuf: [4096]u8 = undefined;
+    const absdir = dirbuf[0..try tmp.dir.realPath(io, &dirbuf)];
+    const main_path = try std.fmt.allocPrint(alloc, "{s}/main.sx", .{absdir});
+
+    var prog = try buildResolved(alloc, io, absdir, main_path);
+
+    var idx = ProgramIndex.init(alloc);
+    defer idx.deinit();
+    idx.module_decls = &prog.decls;
+    idx.namespace_edges = &prog.ns_edges;
+    idx.flat_import_graph = &prog.flat_import_graph;
+    idx.import_graph = &prog.import_graph;
+
+    var rp = resolver.resolve(prog.root, &idx, main_path, alloc);
+    defer rp.deinit();
+
+    // (0) FULL population: every one of the ten domains is non-empty.
+    try std.testing.expect(rp.type_refs.count() > 0);
+    try std.testing.expect(rp.value_refs.count() > 0);
+    try std.testing.expect(rp.callable_refs.count() > 0);
+    try std.testing.expect(rp.namespace_refs.count() > 0);
+    try std.testing.expect(rp.generic_struct_heads.count() > 0);
+    try std.testing.expect(rp.type_fn_heads.count() > 0);
+    try std.testing.expect(rp.protocol_heads.count() > 0);
+    try std.testing.expect(rp.foreign_class_refs.count() > 0);
+    try std.testing.expect(rp.struct_const_refs.count() > 0);
+    try std.testing.expect(rp.ufcs_refs.count() > 0);
+
+    const struct_tag = std.meta.Tag(resolver.RawDeclRef).struct_decl;
+    const fn_tag = std.meta.Tag(resolver.RawDeclRef).fn_decl;
+    const foreign_tag = std.meta.Tag(resolver.RawDeclRef).foreign_class_decl;
+
+    // (1) Foreign-class ref: `o: Obj` is keyed by the exact param type-expr node in
+    //     foreign_class_refs, resolves RAW to the foreign_class_decl author — and is
+    //     NOT mis-recorded into the bare type_refs table.
+    const use_obj = findFn(prog.root, "use_obj") orelse return error.MissingFn;
+    const obj_te = use_obj.data.fn_decl.params[0].type_expr;
+    const obj_ref = rp.foreign_class_refs.get(obj_te) orelse return error.ObjNotKeyed;
+    try std.testing.expect(obj_ref == .authors);
+    try std.testing.expect(obj_ref.authors.own != null);
+    try std.testing.expectEqual(foreign_tag, std.meta.activeTag(obj_ref.authors.own.?.raw));
+    try std.testing.expect(rp.type_refs.get(obj_te) == null);
+
+    // (2) Struct constant: `Phys.GRAVITY` is keyed by its field_access node in
+    //     struct_const_refs and resolves RAW to the owning struct author.
+    var saw_const = false;
+    var sit = rp.struct_const_refs.iterator();
+    while (sit.next()) |e| {
+        const k = e.key_ptr.*;
+        try std.testing.expect(k.data == .field_access); // struct-const keys the access node
+        if (std.mem.eql(u8, k.data.field_access.field, "GRAVITY")) {
+            try std.testing.expect(e.value_ptr.* == .authors);
+            try std.testing.expect(e.value_ptr.authors.own != null);
+            try std.testing.expectEqual(struct_tag, std.meta.activeTag(e.value_ptr.authors.own.?.raw));
+            saw_const = true;
+        }
+    }
+    try std.testing.expect(saw_const);
+
+    // (3a) UFCS alias decl: the `plus :: ufcs adder` node is keyed in ufcs_refs and
+    //      resolves RAW to the target fn (`adder`) author.
+    const plus_decl = findDecl(prog.root, "plus", .ufcs_alias) orelse return error.MissingUfcsAlias;
+    const plus_ref = rp.ufcs_refs.get(plus_decl) orelse return error.UfcsAliasNotKeyed;
+    try std.testing.expect(plus_ref == .authors);
+    try std.testing.expect(plus_ref.authors.own != null);
+    try std.testing.expectEqual(fn_tag, std.meta.activeTag(plus_ref.authors.own.?.raw));
+
+    // (3b) UFCS rewrite site: the `plus(1, 2)` callee identifier is keyed in
+    //      ufcs_refs (NOT callable_refs) and resolves to the SAME target author.
+    var saw_site = false;
+    var uit = rp.ufcs_refs.iterator();
+    while (uit.next()) |e| {
+        const k = e.key_ptr.*;
+        if (k.data == .identifier and std.mem.eql(u8, k.data.identifier.name, "plus")) {
+            try std.testing.expect(e.value_ptr.* == .authors);
+            try std.testing.expect(e.value_ptr.authors.own != null);
+            try std.testing.expectEqual(fn_tag, std.meta.activeTag(e.value_ptr.authors.own.?.raw));
+            saw_site = true;
+        }
+    }
+    try std.testing.expect(saw_site);
+
+    // A UFCS-rewritten callee is NOT also recorded as an ordinary callable head.
+    var cit = rp.callable_refs.iterator();
+    while (cit.next()) |e| {
+        try std.testing.expect(!std.mem.eql(u8, e.key_ptr.*.data.identifier.name, "plus"));
+    }
+}

src/ir/resolver.zig

@@ -187,8 +187,12 @@ fn containsAuthor(list: []const RawAuthor, b: RawAuthor) bool {
 // $pack[i]) SYMBOLICALLY (template/pack ids, never TypeIds). S2.1b adds the
 // namespace-qualified table (`alias.member` resolved via `collectNamespaceAuthors`)
 // and the three HEAD tables (generic-struct / type-fn / protocol), binned by the
-// resolved author's decl kind at `parameterized_type_expr` heads. The remaining
+// resolved author's decl kind at `parameterized_type_expr` heads. S2.1c closes the
-// three tables (foreign-class / struct-const / UFCS) stay empty until S2.1c.
+// set with the final three: a bare reference whose author is a `foreign_class_decl`
+// is routed to `foreign_class_refs`; a `Type.CONST` field access whose base author
+// is a struct carrying that const member fills `struct_const_refs`; and a UFCS
+// alias (`alias :: ufcs target`) plus its rewrite call sites fill `ufcs_refs`. All
+// ten domains are now populated — still PARALLEL / UNCONSUMED / RAW.
 
 /// A symbolic id for one enclosing generic TYPE/VALUE param (`$T`, `$N`), assigned
 /// by the pass and indexing `ResolvedProgram.template_params`. Process-local.
@@ -327,7 +331,9 @@ pub fn resolve(
     var pass = ResolvePass{
         .res = Resolver.init(index, alloc),
         .out = ResolvedProgram.init(alloc),
+        .ufcs_aliases = std.StringHashMap([]const u8).init(alloc),
     };
+    defer pass.ufcs_aliases.deinit();
     pass.visit(root, .{ .source = main_file, .scope = null });
     return pass.out;
 }
@@ -405,11 +411,56 @@ fn classifyHeadKind(raw: RawDeclRef, gs: *bool, tf: *bool, pr: *bool) void {
     }
 }
 
+/// True when an author set resolves to a `foreign_class_decl` — the own author
+/// decides when present, else any flat author. Such a reference is routed to
+/// `foreign_class_refs` (its own domain) instead of the bare type/value table.
+fn authorSetIsForeignClass(set: AuthorSet) bool {
+    if (set.own) |a| return std.meta.activeTag(a.raw) == .foreign_class_decl;
+    for (set.flat) |a| {
+        if (std.meta.activeTag(a.raw) == .foreign_class_decl) return true;
+    }
+    return false;
+}
+
+/// A struct author carrying a `const_decl` member named `field` — the RAW shape
+/// `Type.CONST` field access resolves to. Mirrors the lowering `struct_const_map`
+/// domain, which is struct-level constants only; enums / other decls carry no
+/// const members, so only `struct_decl` matches.
+fn structHasConstMember(raw: RawDeclRef, field: []const u8) bool {
+    return switch (raw) {
+        .struct_decl => |sd| blk: {
+            for (sd.constants) |c| {
+                if (c.data == .const_decl and std.mem.eql(u8, c.data.const_decl.name, field))
+                    break :blk true;
+            }
+            break :blk false;
+        },
+        else => false,
+    };
+}
+
+/// Any author in the set (own or flat) is a struct with a const member `field`.
+fn authorSetHasStructConst(set: AuthorSet, field: []const u8) bool {
+    if (set.own) |a| {
+        if (structHasConstMember(a.raw, field)) return true;
+    }
+    for (set.flat) |a| {
+        if (structHasConstMember(a.raw, field)) return true;
+    }
+    return false;
+}
+
 /// The single owning traversal. Holds the author collector + the `ResolvedProgram`
 /// it populates; threads `Ctx` (ambient source + generic scope) down the tree.
 const ResolvePass = struct {
     res: Resolver,
     out: ResolvedProgram,
+    /// `alias name → target name` for every `ufcs_alias` seen so far on the walk.
+    /// Global (not block-scoped) and populated in traversal order, mirroring
+    /// lowering's flat `ufcs_alias_map`; lets a UFCS-rewrite call site resolve to
+    /// the alias target's author. Scratch — freed when `resolve` returns, NOT part
+    /// of the owned `ResolvedProgram`.
+    ufcs_aliases: std.StringHashMap([]const u8),
 
     /// Visit ONE node, then recurse into its children. A stamped
     /// `node.source_file` (top-level decls, and cross-module fn bodies whose bare
@@ -485,23 +536,35 @@ const ResolvePass = struct {
             .identifier => self.classifyValue(node, here),
             .call => |*c| {
                 if (c.callee.data == .identifier) {
-                    // bare-name callable HEAD — recorded here, not re-walked as a
+                    const cname = c.callee.data.identifier.name;
+                    // a UFCS-alias callee (`alias(args)`, incl. the parser's
+                    // pipe-desugared `x |> alias()`) resolves to the alias TARGET's
+                    // author → ufcs_refs (S2.1c). Any other bare callee is an
+                    // ordinary callable HEAD — recorded here, not re-walked as a
                     // value ref.
-                    self.recordAuthors(&self.out.callable_refs, c.callee, c.callee.data.identifier.name, here.source);
+                    if (self.ufcs_aliases.get(cname)) |target| {
+                        self.recordAuthorsInto(&self.out.ufcs_refs, c.callee, target, here.source);
+                    } else {
+                        self.recordAuthors(&self.out.callable_refs, c.callee, cname, here.source);
+                    }
                 } else {
                     self.visit(c.callee, here);
                 }
                 self.visitAll(c.args, here);
             },
             .field_access => |*fa| {
-                // `alias.member` whose base alias is a namespace import edge of the
+                // `alias.member` whose base is a namespace import edge of the
                 // ambient source resolves via `collectNamespaceAuthors` into the
-                // namespace-qualified table (S2.1b). A non-alias bare receiver
+                // namespace-qualified table (S2.1b). Otherwise `Type.CONST` — a base
-                // (struct-const / UFCS / local value) stays unclassified — S2.1c —
+                // resolving to a struct author that carries the named const member —
-                // and is not walked as a value ref; a compound receiver is recursed
+                // fills `struct_const_refs` (S2.1c). A receiver that is neither (a
-                // so its inner refs are collected.
+                // local value / instance field access) records nothing and is not
+                // walked as a value ref; a compound receiver is recursed so its
+                // inner refs are collected.
                 if (fa.object.data == .identifier) {
-                    self.classifyNamespaceQualified(node, fa.object.data.identifier.name, fa.field, here.source);
+                    const base = fa.object.data.identifier.name;
+                    if (!self.classifyNamespaceQualified(node, base, fa.field, here.source))
+                        _ = self.classifyStructConst(node, base, fa.field, here.source);
                 } else {
                     self.visit(fa.object, here);
                 }
@@ -675,9 +738,17 @@ const ResolvePass = struct {
             .foreign_expr,
             .library_decl,
             .framework_decl,
-            .ufcs_alias,
             .c_import_decl,
             => {},
+
+            // `alias :: ufcs target` — record the alias→target binding (the
+            // target's RAW author) keyed by the decl node, and remember the alias
+            // name so its rewrite call sites resolve to the same target. The map is
+            // global / traversal-ordered, mirroring lowering's flat `ufcs_alias_map`.
+            .ufcs_alias => |ua| {
+                self.ufcs_aliases.put(ua.name, ua.target) catch @panic("resolve: OOM");
+                self.recordAuthorsInto(&self.out.ufcs_refs, node, ua.target, here.source);
+            },
         }
     }
 
@@ -722,8 +793,20 @@ const ResolvePass = struct {
 
     /// RAW author collection for a bare name. Only recorded when the name has ≥1
     /// visible author (own or flat); a builtin / local / undeclared spelling has
-    /// none and is omitted — this is what keeps the tables to genuine authors.
+    /// none and is omitted — this is what keeps the tables to genuine authors. A
+    /// name whose author is a `foreign_class_decl` is routed to `foreign_class_refs`
+    /// (its own S2.1c domain) instead of the passed bare type/value/callable table.
     fn recordAuthors(self: *ResolvePass, table: *NodeRefTable, node: *const ast.Node, name: []const u8, from: []const u8) void {
+        const set = self.res.collectVisibleAuthors(name, from, .user_bare_flat);
+        if (set.distinctCount() == 0) return;
+        const dest = if (authorSetIsForeignClass(set)) &self.out.foreign_class_refs else table;
+        self.replaceRef(dest, node, .{ .authors = set });
+    }
+
+    /// RAW author collection into an explicit table, with NO foreign-class routing —
+    /// the destination domain is already chosen by the caller (UFCS rewrite sites
+    /// and alias decls, whose target is always a free function).
+    fn recordAuthorsInto(self: *ResolvePass, table: *NodeRefTable, node: *const ast.Node, name: []const u8, from: []const u8) void {
         const set = self.res.collectVisibleAuthors(name, from, .user_bare_flat);
         if (set.distinctCount() == 0) return;
         self.replaceRef(table, node, .{ .authors = set });
@@ -731,16 +814,34 @@ const ResolvePass = struct {
 
     /// `alias.member`: when `alias` is a namespace import edge of `from`, resolve
     /// `member` against that already-selected target via `collectNamespaceAuthors`
-    /// (NO graph walk) and record it into the namespace-qualified table. A base that
+    /// (NO graph walk) and record it into the namespace-qualified table. Returns
-    /// is not a namespace alias (struct-const / UFCS / local value — S2.1c) records
+    /// whether it recorded — a base that is not a namespace alias records nothing
-    /// nothing here.
+    /// here and lets the caller try the struct-const path.
-    fn classifyNamespaceQualified(self: *ResolvePass, node: *const ast.Node, alias: []const u8, member: []const u8, from: []const u8) void {
+    fn classifyNamespaceQualified(self: *ResolvePass, node: *const ast.Node, alias: []const u8, member: []const u8, from: []const u8) bool {
-        const edges = self.res.index.namespace_edges orelse return;
+        const edges = self.res.index.namespace_edges orelse return false;
-        const aliases = edges.get(from) orelse return;
+        const aliases = edges.get(from) orelse return false;
-        const target = aliases.get(alias) orelse return;
+        const target = aliases.get(alias) orelse return false;
         const set = self.res.collectNamespaceAuthors(target, member);
-        if (set.distinctCount() == 0) return;
+        if (set.distinctCount() == 0) return false;
         self.replaceRef(&self.out.namespace_refs, node, .{ .authors = set });
+        return true;
+    }
+
+    /// `Type.CONST`: when `base` resolves to a struct author carrying a const member
+    /// named `member`, record the base's RAW author set into `struct_const_refs`
+    /// (keyed by the field-access node) — the owning-type identity the constant
+    /// lives on. A base with authors but no matching const member, or no author at
+    /// all (a local value receiver), records nothing and releases its allocation.
+    /// Returns whether it recorded.
+    fn classifyStructConst(self: *ResolvePass, node: *const ast.Node, base: []const u8, member: []const u8, from: []const u8) bool {
+        const set = self.res.collectVisibleAuthors(base, from, .user_bare_flat);
+        if (set.distinctCount() == 0) return false;
+        if (!authorSetHasStructConst(set, member)) {
+            if (set.flat.len > 0) self.out.alloc.free(set.flat);
+            return false;
+        }
+        self.replaceRef(&self.out.struct_const_refs, node, .{ .authors = set });
+        return true;
     }
 
     /// A parameterized head (`Name(args)`) binned by its resolved author's decl