Keep the closure when a cast instantiates a capturing untyped arrow

tslang/lib/TypeScript/MLIRGenCast.cpp

@@ -2044,7 +2044,7 @@ namespace mlirgen
         }
     }
 
-    mlir::LogicalResult MLIRGenImpl::verifyFunctionCastRules(mlir::Location location, mlir::Type type, mlir::Value value, mlir::Type valueType, const GenContext &genContext)
+    mlir::LogicalResult MLIRGenImpl::verifyFunctionCastRules(mlir::Location location, mlir::Type type, mlir::Value &value, mlir::Type &valueType, const GenContext &genContext)
     {
         if (mth.isAnyFunctionType(valueType) && mth.isAnyFunctionType(type)) {
 
@@ -2053,6 +2053,17 @@ namespace mlirgen
                 // need to instantiate generic method
                 auto result = instantiateSpecializedFunction(location, value, type, genContext);
                 EXIT_IF_FAILED(result);
+
+                // An arrow that captures comes back as a new value, the closure bound over its
+                // captured variables; the old reference is the bare function and calling it reads
+                // the captures through a null pointer (`new W((v) => { seen += 1; })`). Without
+                // captures the reference was retyped in place.
+                if (auto resultValue = V(result))
+                {
+                    value = resultValue;
+                }
+
+                valueType = value.getType();
             }
 
             // A C variadic function is called with C's variadic convention and a TypeScript

tslang/lib/TypeScript/MLIRGenImpl.h

@@ -14253,7 +14253,7 @@ class MLIRGenImpl
     // union or optional or any or opaque source type
     std::optional<ValueOrLogicalResult> castFromSourceSpecialCases(mlir::Location location, mlir::Type type, mlir::Value value, mlir::Type valueType, const GenContext &genContext);
 
-    mlir::LogicalResult verifyFunctionCastRules(mlir::Location location, mlir::Type type, mlir::Value value, mlir::Type valueType, const GenContext &genContext);
+    mlir::LogicalResult verifyFunctionCastRules(mlir::Location location, mlir::Type type, mlir::Value &value, mlir::Type &valueType, const GenContext &genContext);
 
     // cast ext method to bound method
     std::optional<ValueOrLogicalResult> castExtensionFunctionType(mlir::Location location, mlir::Type type, mlir::Value value, mlir::Type valueType);

tslang/test/tester/CMakeLists.txt

@@ -597,6 +597,7 @@ tslang_add_test(NAME test-compile-00-try-cleanup-then-catch COMMAND test-runner
 tslang_add_test(NAME test-compile-00-try-empty-catch COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00try_empty_catch.ts")
 tslang_add_test(NAME test-compile-00-global-union-from-call COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00global_union_from_call.ts")
 tslang_add_test(NAME test-compile-00-capture-in-new-arguments COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00capture_in_new_arguments.ts")
+tslang_add_test(NAME test-compile-00-capture-in-new-untyped-arrow COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00capture_in_new_untyped_arrow.ts")
 tslang_add_test(NAME test-compile-01-class-new COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/01class_new.ts")
 tslang_add_test(NAME test-compile-00-class-stack COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00class_stack.ts")
 tslang_add_test(NAME test-compile-00-class-static COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00class_static.ts")
@@ -1202,6 +1203,7 @@ tslang_add_test(NAME test-jit-00-try-cleanup-then-catch COMMAND test-runner -jit
 tslang_add_test(NAME test-jit-00-try-empty-catch COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00try_empty_catch.ts")
 tslang_add_test(NAME test-jit-00-global-union-from-call COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00global_union_from_call.ts")
 tslang_add_test(NAME test-jit-00-capture-in-new-arguments COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00capture_in_new_arguments.ts")
+tslang_add_test(NAME test-jit-00-capture-in-new-untyped-arrow COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00capture_in_new_untyped_arrow.ts")
 tslang_add_test(NAME test-jit-01-class-new COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/01class_new.ts")
 tslang_add_test(NAME test-jit-00-class-stack COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00class_stack.ts")
 tslang_add_test(NAME test-jit-00-class-static COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00class_static.ts")
@@ -2146,6 +2148,7 @@ set(TSLANG_CORPUS
     00try_scope_exit_through_finally.ts
     00try_jump_from_catch.ts
     00capture_in_new_arguments.ts
+    00capture_in_new_untyped_arrow.ts
     00cast_to_f32.ts
     00catch_untyped_value.ts
     00catch_value.ts

tslang/test/tester/tests/00capture_in_new_untyped_arrow.ts

@@ -0,0 +1,66 @@
+// An arrow without parameter types, `(v) => ...`, is generic until something gives it a type. As a
+// `new` argument it gets one when it is cast to the constructor parameter's type, and the cast
+// instantiated it there - but when the arrow captured a local, the instantiation built the closure
+// over the captured variables and the cast went on with the bare function instead. The constructor
+// stored a function whose captures were a null pointer, and the first call crashed - under every
+// memory model, so it is a front-end bug. A non-capturing arrow, or one with typed parameters,
+// never went that way.
+
+class ParamProperty {
+    constructor(private f: (v: number) => void) {}
+
+    run(v: number) {
+        this.f(v);
+    }
+}
+
+class StoredField {
+    f: (v: number) => void;
+
+    constructor(f: (v: number) => void) {
+        this.f = f;
+    }
+
+    run(v: number) {
+        this.f(v);
+    }
+}
+
+class Mapper {
+    constructor(private f: (v: number) => number) {}
+
+    apply(v: number) {
+        return this.f(v);
+    }
+}
+
+let globalSeen: number = 0;
+
+function main() {
+    let seen: number = 0;
+    const p = new ParamProperty((v) => {
+        seen += v;
+    });
+    p.run(1);
+    p.run(2);
+    assert(seen == 3, "a capturing untyped arrow in a parameter property");
+
+    let total: number = 0;
+    const s = new StoredField((v) => {
+        total += v;
+    });
+    s.run(5);
+    assert(total == 5, "a capturing untyped arrow stored in a field");
+
+    const k = 10;
+    const m = new Mapper((v) => v * k);
+    assert(m.apply(4) == 40, "a capturing untyped arrow returning a value");
+
+    const g = new ParamProperty((v) => {
+        globalSeen += v;
+    });
+    g.run(7);
+    assert(globalSeen == 7, "a non-capturing untyped arrow");
+
+    print("done.");
+}