test(compiler): unit helpers run inference; retarget borrow-escape fixture

Wire Gcinfer.infer into runner.ml's owner_str/emit_str so the unit tests
classify GC-ness identically to the driver (prerequisite for removing @gc: its
tests read the golden .wo through the library).

That exposed owner-err/borrow-escape.wo, which tested WO-E304 on *class*
escapes — now legally demand-promoted. Retargeted it to CONTAINER (`multi Text`)
escapes, which are owned and never promoted, so it still exercises the three
WO-E304 shapes (stored-in-field, returned, moved-to-take). Assertion positions
+ golden re-blessed.

Verified: woc-test 566/0, test_diag 14/0, oop-e2e 79/0.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

compiler/test/golden/owner-err/borrow-escape.expected

@@ -1,19 +1,19 @@
-owner-err/borrow-escape.wo:9:16: error WO-E304: borrow of `other` cannot be stored in `self.box` — borrows cannot outlive their scope
-    self.box = other
-               ^
+owner-err/borrow-escape.wo:9:18: error WO-E304: borrow of `other` cannot be stored in `self.items` — borrows cannot outlive their scope
+    self.items = other
+                 ^
   owner-err/borrow-escape.wo:8:12: `other` is borrowed here — declare it `take other: T` to pass ownership in
-    fn adopt(other: Box) {
+    fn adopt(other: multi Text) {
              ^
 
-owner-err/borrow-escape.wo:18:10: error WO-E304: borrow of `h.box` escapes `leak` — borrows cannot outlive their scope
-  return h.box
+owner-err/borrow-escape.wo:18:10: error WO-E304: borrow of `h.items` escapes `leak` — borrows cannot outlive their scope
+  return h.items
          ^
   owner-err/borrow-escape.wo:17:9: `h` is borrowed here — declare it `take h: T` to pass ownership in
-  fn leak(h: Holder) -> Box {
+  fn leak(h: Holder) -> multi Text {
           ^
 
-owner-err/borrow-escape.wo:22:15: error WO-E304: borrow of `h.box` cannot be passed to `take b` — borrows cannot outlive their scope
-  return keep(h.box)
+owner-err/borrow-escape.wo:22:15: error WO-E304: borrow of `h.items` cannot be passed to `take b` — borrows cannot outlive their scope
+  return keep(h.items)
               ^
   owner-err/borrow-escape.wo:21:10: `h` is borrowed here — declare it `take h: T` to pass ownership in
   fn stash(h: Holder) -> Int {

compiler/test/golden/owner-err/borrow-escape.wo

@@ -1,23 +1,23 @@
-class Box {
-  n: Int
-}
-
+-- Iteration 7b: WO-E304 borrow escapes, using CONTAINER values (`multi Text`).
+-- A class value that escapes is demand-promoted to traced, so the illustrative
+-- escapes must be containers, which are owned and never promoted. Mirrors the
+-- run/borrow-escape-return corpus case (a class escape, now legal).
 class Holder {
-  box: Box
+  items: multi Text
 
-  fn adopt(other: Box) {
-    self.box = other
+  fn adopt(other: multi Text) {
+    self.items = other
   }
 }
 
-fn keep(take b: Box) -> Int {
+fn keep(take b: multi Text) -> Int {
   return 0
 }
 
-fn leak(h: Holder) -> Box {
-  return h.box
+fn leak(h: Holder) -> multi Text {
+  return h.items
 }
 
 fn stash(h: Holder) -> Int {
-  return keep(h.box)
+  return keep(h.items)
 }

compiler/test/runner.ml

@@ -39,6 +39,7 @@ module Parser = Woc_lib.Parser
 module Dump = Woc_lib.Dump
 module Types = Woc_lib.Types
 module Owner = Woc_lib.Owner
+module Gcinfer = Woc_lib.Gcinfer
 module Emit = Woc_lib.Emit
 module Disasm = Woc_lib.Disasm
 
@@ -1807,6 +1808,7 @@ let owner_str ~file src =
   let toks = Lexer.tokenize collector ~file src in
   let prog = Parser.parse collector ~file toks in
   let syms, () = Types.typecheck ~file prog collector in
+  let syms = Gcinfer.infer [ (file, prog) ] syms in
   let tables = Owner.analyze ~file prog syms collector in
   (tables, collector)
 
@@ -1819,6 +1821,7 @@ let emit_str ~file src =
   let toks = Lexer.tokenize collector ~file src in
   let prog = Parser.parse collector ~file toks in
   let syms, () = Types.typecheck ~file prog collector in
+  let syms = Gcinfer.infer [ (file, prog) ] syms in
   let tables = Owner.analyze ~file prog syms collector in
   (* Single-file helper (every golden fixture is one file): its own
      module is "." and that module's own symbols are exactly `syms` —
@@ -1929,7 +1932,7 @@ let () =
      field, returned, moved out to a `take` parameter. *)
   match owner_err_fixture "borrow-escape" with
   | [ store; ret; take ] ->
-    check_site "borrow-escape (stored in a field)" ~code:"WO-E304" ~line:9 ~col:16 ~rel_line:8
+    check_site "borrow-escape (stored in a field)" ~code:"WO-E304" ~line:9 ~col:18 ~rel_line:8
       ~rel_col:12 store;
     check_site "borrow-escape (returned)" ~code:"WO-E304" ~line:18 ~col:10 ~rel_line:17 ~rel_col:9
       ret;
@@ -1937,7 +1940,7 @@ let () =
       ~rel_line:21 ~rel_col:10 take;
     (* spec section 6's own wording for this diagnostic *)
     check "borrow-escape: names the place and the function it escapes"
-      (Option.is_some (find_substring ~needle:"borrow of `h.box` escapes `leak`" ret.Diag.message))
+      (Option.is_some (find_substring ~needle:"borrow of `h.items` escapes `leak`" ret.Diag.message))
   | ds ->
     check_eq "borrow-escape: exactly three ownership errors" ~expected:3 ~actual:(List.length ds)
       string_of_int