Fix

Author: Changqing-JING

src/resolver.ts

@@ -3449,13 +3449,12 @@ export class Resolver extends DiagnosticEmitter {
           // A generic method cannot implement a non-generic interface method
           // because monomorphization requires a concrete type to generate code,
           // but virtual dispatch through the interface has no type arguments.
-          let ifaceMember = unimplemented.get(memberName);
-          if (ifaceMember
+          if (unimplemented.has(memberName)
             && member.kind == ElementKind.FunctionPrototype
-            && ifaceMember.kind == ElementKind.FunctionPrototype
+            && unimplemented.get(memberName)!.kind == ElementKind.FunctionPrototype
           ) {
             let memberTypeParams = (<FunctionPrototype>member).typeParameterNodes;
-            let ifaceTypeParams = (<FunctionPrototype>ifaceMember).typeParameterNodes;
+            let ifaceTypeParams = (<FunctionPrototype>unimplemented.get(memberName)).typeParameterNodes;
             let numMemberTypeParams = memberTypeParams ? memberTypeParams.length : 0;
             let numIfaceTypeParams = ifaceTypeParams ? ifaceTypeParams.length : 0;
             if (numMemberTypeParams != numIfaceTypeParams) continue;

tests/compiler/override-typeparam-mismatch.json

@@ -1,6 +1,7 @@
 {
   "asc_flags": [],
   "stderr": [
-    "TS2515: Non-abstract class 'override-typeparam-mismatch/CC' does not implement inherited abstract member 'foo' from 'override-typeparam-mismatch/I'."
+    "TS2515: Non-abstract class 'override-typeparam-mismatch/CC' does not implement inherited abstract member 'foo' from 'override-typeparam-mismatch/I'.",
+    "EOF"
   ]
 }

tests/compiler/override-typeparam-mismatch.ts

@@ -10,3 +10,5 @@ class CC implements I {
 
 let c:I = new CC();
 c.foo(1);
+
+ERROR("EOF");