bug fix 2727: class member function type is assigned to a normal function type

Author: Changqing-JING

src/compiler.ts

@@ -6611,13 +6611,17 @@ export class Compiler extends DiagnosticEmitter {
         if (!overrideInstance.is(CommonFlags.Compiled)) continue; // errored
         let overrideType = overrideInstance.type;
         let originalType = instance.type;
-        if (!overrideType.isAssignableTo(originalType)) {
+
+        assert(originalType.getSignature() != null && overrideType.getSignature() != null);
+        if (!(overrideType.getSignature() as Signature).isAssignableTo(originalType.getSignature() as Signature, true)) {
           this.error(
             DiagnosticCode.Type_0_is_not_assignable_to_type_1,
             overrideInstance.identifierNode.range, overrideType.toString(), originalType.toString()
           );
           continue;
         }
+        
+        
         // TODO: additional optional parameters are not permitted by `isAssignableTo` yet
         let overrideSignature = overrideInstance.signature;
         let overrideParameterTypes = overrideSignature.parameterTypes;

src/types.ts

@@ -1062,9 +1062,12 @@ export class Signature {
       }
     } else {
       // check `this` type (invariant)
-      if (thisThisType) {
-        if (targetThisType != targetThisType) return false;
-      } else if (targetThisType) {
+      if (
+        (thisThisType == null && targetThisType != null) ||
+        (thisThisType != null && targetThisType == null)
+      ) {
+        return false;
+      } else if (thisThisType != null && targetThisType != null && targetThisType.isAssignableTo(thisThisType)) {  
         return false;
       }
     }

tests/compiler/class-member-function-as-parameter.json

@@ -0,0 +1,8 @@
+{
+  "asc_flags": [],
+  "stderr": [
+    "TS2322: Type '(this: class-member-function-as-parameter/C, i32) => i32' is not assignable to type '(i32) => i32'.",
+    "TS2322: Type '() => void' is not assignable to type '(this: class-member-function-as-parameter/B) => void'.",
+    "EOF"
+  ]
+}

tests/compiler/class-member-function-as-parameter.ts

@@ -0,0 +1,52 @@
+class C {
+  aa: i32 = 1;
+  callback(a: i32): i32 {
+    return this.aa + a + 3;
+  }
+}
+
+function expectCallback(c1: (arg0: i32) => i32): i32 {
+  return c1(4);
+}
+
+export function fut(): i32 {
+  const c1 = new C();
+  return expectCallback(c1.callback);
+}
+
+fut();
+
+class A {
+  foo(): void {
+    console.log("A");
+  }
+}
+
+class B extends A {
+  foo(): void {
+    console.log("B");
+  }
+}
+
+function foo(): void {
+  console.log("nothing");
+}
+
+function consume(callback: (this: B) => void): void {
+  const b = new B();
+  callback.call(b);
+}
+
+export function testNull(): void {
+  consume(foo); // This should (and does) error; this is fine.
+}
+
+export function testA(): void {
+  const a = new A();
+  consume(a.foo); // This shouldn't error
+}
+
+testNull();
+testA();
+
+ERROR("EOF");