1 files changed, 79 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/wasm/gc/function_subtyping.js b/js/src/jit-test/tests/wasm/gc/function_subtyping.js
new file mode 100644
index 0000000000..6b4e719a74
--- /dev/null
+++ b/js/src/jit-test/tests/wasm/gc/function_subtyping.js
@@ -0,0 +1,79 @@
+// |jit-test| skip-if: !wasmGcEnabled()
+
+// Validate rules for function subtyping:
+// - Same number of parameters and results
+// - Function return types are covariant
+// - Function parameter types are contravariant
+wasmValidateText(
+`(module
+    (type $A (struct (field i32)))
+    (type $B (sub $A (struct (field i32) (field i32))))
+    (type $C (sub $B (struct (field i32) (field i32) (field i64))))
+    (type $D (sub $B (struct (field i32) (field i32) (field f32))))
+
+    ;; Same types (invariant)
+    (type $func1 (func (param (ref $A) (ref $A)) (result (ref $C))))
+    (type $func2 (sub $func1 (func (param (ref $A) (ref $A)) (result (ref $C)))))
+
+    ;; Covariant return types are valid
+    (type $func3 (func (param (ref $A) (ref $A)) (result (ref $B))))
+    (type $func4 (sub $func3 (func (param (ref $A) (ref $A)) (result (ref $C)))))
+    (type $func5 (func (param (ref $A) (ref $A)) (result (ref $A) (ref $B))))
+    (type $func6 (sub $func5 (func (param (ref $A) (ref $A)) (result (ref $D) (ref $C)))))
+
+    ;; Contravariant parameter types are valid
+    (type $func7 (func (param (ref $A) (ref $C)) (result (ref $C))))
+    (type $func8 (sub $func7 (func (param (ref $A) (ref $B)) (result (ref $C)))))
+    (type $func9 (func (param (ref $D) (ref $C)) (result (ref $C))))
+    (type $func10 (sub $func9 (func (param (ref $A) (ref $B)) (result (ref $C)))))
+
+    ;; Mixing covariance and contravariance
+    (type $func11 (func (param (ref $D) (ref $C)) (result (ref $A))))
+    (type $func12 (sub $func11 (func (param (ref $A) (ref $B)) (result (ref $C)))))
+)
+`);
+
+// Validate that incorrect subtyping examples are failing as expected
+const typeError = /incompatible super type/;
+
+var code =`
+(module
+    (type $A (struct (field i32)))
+    (type $B (sub $A (struct (field i32) (field i32))))
+    (type $C (sub $B (struct (field i32) (field i32) (field i64))))
+    (type $D (sub $B (struct (field i32) (field i32) (field f32))))
+
+    ;; Not the same number of arguments/results
+    (type $func1 (func (param (ref $A) (ref $A)) (result (ref $C))))
+    (type $func2 (sub $func1 (func (param (ref $A) (ref $A)) (result (ref $C) (ref $A)))))
+)`;
+
+wasmFailValidateText(code, typeError);
+
+code =`
+(module
+    (type $A (struct (field i32)))
+    (type $B (sub $A (struct (field i32) (field i32))))
+    (type $C (sub $B (struct (field i32) (field i32) (field i64))))
+    (type $D (sub $B (struct (field i32) (field i32) (field f32))))
+
+    ;; Contravariant result types are invalid
+    (type $func3 (func (param (ref $A) (ref $A)) (result (ref $C))))
+    (type $func4 (sub $func3 (func (param (ref $A) (ref $A)) (result (ref $A)))))
+)`;
+
+wasmFailValidateText(code, typeError);
+
+code =`
+(module
+    (type $A (struct (field i32)))
+    (type $B (sub $A (struct (field i32) (field i32))))
+    (type $C (sub $B (struct (field i32) (field i32) (field i64))))
+    (type $D (sub $B (struct (field i32) (field i32) (field f32))))
+
+    ;; Covariant parameters are invalid
+    (type $func5 (func (param (ref $A) (ref $A)) (result (ref $C))))
+    (type $func6 (sub $func5 (func (param (ref $B) (ref $A)) (result (ref $C)))))
+)`;
+
+wasmFailValidateText(code, typeError);