fix: Type checker does not detect a signature mismatch

Fixes: #2727

Author: Changqing-JING

src/compiler.ts

@@ -6609,17 +6609,18 @@ export class Compiler extends DiagnosticEmitter {
  for (let i = 0, k = overrideInstances.length; i < k; ++i) {
  let overrideInstance = overrideInstances[i];
  if (!overrideInstance.is(CommonFlags.Compiled)) continue; // errored
- let overrideType = overrideInstance.type;
- let originalType = instance.type;
- if (!overrideType.isAssignableTo(originalType)) {
+
+ let overrideSignature = overrideInstance.signature;
+ let originalSignature = instance.signature;
+
+ if (!overrideSignature.isAssignableTo(originalSignature, true)) {
  this.error(
  DiagnosticCode.Type_0_is_not_assignable_to_type_1,
- overrideInstance.identifierNode.range, overrideType.toString(), originalType.toString()
+ overrideInstance.identifierNode.range, overrideSignature.toString(), originalSignature.toString()
  );
  continue;
  }
  // TODO: additional optional parameters are not permitted by `isAssignableTo` yet
- let overrideSignature = overrideInstance.signature;
  let overrideParameterTypes = overrideSignature.parameterTypes;
  let overrideNumParameters = overrideParameterTypes.length;
  let paramExprs = new Array<ExpressionRef>(1 + overrideNumParameters);

src/types.ts

@@ -1051,22 +1051,14 @@ export class Signature {
  isAssignableTo(target: Signature, checkCompatibleOverride: bool = false): bool {
  let thisThisType = this.thisType;
  let targetThisType = target.thisType;
- if (checkCompatibleOverride) {
- // check kind of `this` type
- if (thisThisType) {
- if (!targetThisType || !thisThisType.canExtendOrImplement(targetThisType)) {
- return false;
- }
- } else if (targetThisType) {
- return false;
- }
- } else {
- // check `this` type (invariant)
- if (thisThisType) {
- if (targetThisType != targetThisType) return false;
- } else if (targetThisType) {
- return false;
- }
+
+ if (thisThisType && targetThisType) {
+ const compatibleThisType = checkCompatibleOverride 
+ ? thisThisType.canExtendOrImplement(targetThisType)
+ : targetThisType.isAssignableTo(thisThisType);
+ if (!compatibleThisType) return false; 
+ } else if (thisThisType || targetThisType) {
+ return false;
  }
 
  // check rest parameter

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

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

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

@@ -0,0 +1,20 @@
+class A {
+ foo(): void { }
+}
+
+class B extends A {
+ foo(): void { }
+}
+
+function foo(): void { }
+
+function consumeA(callback: (this: A) => void): void { }
+function consumeB(callback: (this: B) => void): void { }
+
+const a = new A();
+const b = new B();
+
+consumeB(a.foo); // shouldn't error
+consumeA(foo); // should error
+consumeA(b.foo); // should error
+ERROR("EOF");