From 72e890d5aa892257b5c227bc89e66e92c5327da0 Mon Sep 17 00:00:00 2001
From: Hojun-Cho <ghwns6743@gmail.com>
Date: Fri, 14 Aug 2026 11:14:52 +0900
Subject: [PATCH] ww: classify imported call returns canonically

---
 selfhost/cmd/wcc/cgenutil.ww | 21 +++++++++++++--------
 test/byteid/wwi_test.ww      | 12 +++++++++---
 2 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/selfhost/cmd/wcc/cgenutil.ww b/selfhost/cmd/wcc/cgenutil.ww
index d71d1465..8a1bfe5f 100644
--- a/selfhost/cmd/wcc/cgenutil.ww
+++ b/selfhost/cmd/wcc/cgenutil.ww
@@ -2492,13 +2492,20 @@ fn sretretsizetn(c: *cgen, t: *syntax.tinfo) i32 = {
 	return 0;
 };
 
-// callsretsize — if N_CALL `n`'s callee returns a plain TY_STRUCT
-// > 24B, return its natural size; else 0. Wraps sretretsize over the
-// callee's resolved return type, used by cglet / cgassign receive
-// sites and cgcall to detect sret at the receive / emit boundaries.
+// callsretsize — classify an N_CALL from the checker-stamped result type.
+// The callee's return AST can belong to an imported interface source whose
+// private canonical qualifier is deliberately invisible in the caller's file
+// scope. Re-resolving that spelling here loses the canonical type and can
+// select the wrong return ABI. Cstage classifies the checked Type directly;
+// sretretsizetn is its isomorphic tinfo path.
 fn callsretsize(c: *cgen, n: *syntax.node) i32 = {
 	if (n == nil) { return 0; };
 	if (n.kind != syntax.nkind.N_CALL) { return 0; };
+	if (n.type_ != nil) {
+		return sretretsizetn(c, n.type_: *syntax.tinfo);
+	};
+	// Raw cgen-only callers may supply an unchecked AST. Retain their
+	// historical name-based fallback; production checked calls never take it.
 	let callee: *syntax.node = n.lhs;
 	if (callee == nil) { return 0; };
 	let cn: str;
@@ -2519,10 +2526,8 @@ fn callsretsize(c: *cgen, n: *syntax.node) i32 = {
 	};
 	if (cn.len == 0) { return 0; };
 	let rtyp: *syntax.node = fnretlookupmod(c, cn, cmod);
-	// #129: sretretsize must see the CALLEE's module context so
-	// aliassamemod resolves aliases from the callee's module (not the
-	// caller's). Mirrors cstage operating on resolved Type* objects
-	// (type_chase_named never has this confusion). Swap + restore.
+	// The unchecked fallback still needs the callee module for its
+	// same-module alias preference; checked production calls bypass it above.
 	let savedmod: str = c.curmod;
 	if (cmod.len > 0) { c.curmod = cmod; };
 	let r: i32 = sretretsize(c, rtyp);
diff --git a/test/byteid/wwi_test.ww b/test/byteid/wwi_test.ww
index d47fb60e..08d2d331 100644
--- a/test/byteid/wwi_test.ww
+++ b/test/byteid/wwi_test.ww
@@ -224,10 +224,16 @@ fn m2positive(pkg: str) void = {
 		fail("qualified", "cs.wwi != ww.wwi");
 	};
 	let body: str = testenv.readfile(cs);
-	if (!testenv.has(body, "export fn use(x: dep.Clash) i32;")) {
-		fail("qualified", ".wwi dropped the qualified signature");
+	if (!testenv.has(body, "import __wwi_612e646570 a.dep;\n")
+	    || !testenv.has(body,
+		"export fn use(x: __wwi_612e646570.Clash) i32;")) {
+		fail("qualified", ".wwi did not canonicalize the qualified signature");
 	};
-	if (!testenv.has(body, "//ww:module a.dep\n")
+	if (testenv.has(body, "export fn use(x: dep.Clash) i32;")) {
+		fail("qualified", ".wwi retained the source-file qualifier");
+	};
+	if (!testenv.has(body,
+		"//ww:module a.dep\npackage __wwi_612e646570;\n")
 	    || !testenv.has(body, "export type Clash = struct { x: i32 };")) {
 		fail("qualified", ".wwi omitted the signature's origin-owned type fact");
 	};