src/compiler.ts

@@ -6618,6 +6618,7 @@ export class Compiler extends DiagnosticEmitter {
     );
     let overrideInstances = this.resolver.resolveOverrides(instance);
     if (overrideInstances) {
+      let mostRecentInheritanceMapping = new Map<Class, Class>();
       for (let i = 0, k = overrideInstances.length; i < k; ++i) {
         let overrideInstance = overrideInstances[i];
         if (!overrideInstance.is(CommonFlags.Compiled)) continue; // errored
@@ -6680,7 +6681,13 @@ export class Compiler extends DiagnosticEmitter {
             if (instanceMembers && instanceMembers.has(instance.declaration.name.text)) {
               continue; // skip those not inheriting
             }
-            builder.addCase(extender.id, stmts);
+            if (
+              !mostRecentInheritanceMapping.has(extender) ||
+              !assert(mostRecentInheritanceMapping.get(extender)).extends(classInstance)
+            ) {
+              mostRecentInheritanceMapping.set(extender, classInstance);
+              builder.addOrReplaceCase(extender.id, stmts);
+            }
           }
         }
       }

src/module.ts

@@ -3418,16 +3418,32 @@ export class SwitchBuilder {
     this.condition = condition;
   }
 
+  /** Links a case to the specified branch, replace old case if it is linked. */
+  addOrReplaceCase(value: i32, code: ExpressionRef[]): void {
+    const valueIndex = this.values.indexOf(value);
+    const codeIndex =  this.addCode(code);
+    if (valueIndex >= 0) {
+      this.indexes[valueIndex] = codeIndex;
+    } else {
+      this.values.push(value);
+      this.indexes.push(codeIndex);
+    }
+  }
+
   /** Links a case to the specified branch. */
   addCase(value: i32, code: ExpressionRef[]): void {
+    this.values.push(value);
+    this.indexes.push(this.addCode(code));
+  }
+
+  private addCode(code: ExpressionRef[]): i32 {
     let cases = this.cases;
     let index = cases.indexOf(code);
     if (index < 0) {
       index = cases.length;
       cases.push(code);
     }
-    this.values.push(value);
-    this.indexes.push(index);
+    return index;
   }
 
   /** Links the default branch. */

tests/compiler/class-override.json

@@ -0,0 +1,4 @@
+{
+  "asc_flags": [
+  ]
+}

tests/compiler/class-override.ts

@@ -0,0 +1,24 @@
+export function fn(n: i32): i32 {
+  return x.f(n);
+}
+
+class A {
+  f(a: i32): i32 {
+    return a + 1;
+  }
+}
+class B extends A {
+  f(a: i32): i32 {
+    return super.f(a) + 10;
+  }
+}
+class C extends B {
+  f(a: i32): i32 {
+    return super.f(a) + 100;
+  }
+}
+class D extends C {}
+
+let x: A = new D();
+
+assert(fn(0) == 111);