fix #2727:

class member function type is assigned to a normal function type

Author: Changqing-JING

src/types.ts

@@ -1063,7 +1063,7 @@ export class Signature {
     } else {
       // check `this` type (invariant)
       if (thisThisType) {
-        if (targetThisType != targetThisType) return false;
+        if (targetThisType == null) return false;
       } else if (targetThisType) {
         return false;
       }

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

@@ -0,0 +1,6 @@
+{
+  "asc_flags": [],
+  "stderr": [
+    "TS2322: Type '(this: class-member-function-as-parameter/C, i32) => i32' is not assignable to type '(i32) => i32'."
+  ]
+}

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

@@ -0,0 +1,15 @@
+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);
+}