microsoft · ahejlsberg · Dec 5, 2016 · Dec 4, 2016 · Dec 4, 2016 · Dec 4, 2016
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -6033,6 +6033,9 @@ namespace ts {
 
         function getIndexedAccessType(objectType: Type, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode) {
             if (maybeTypeOfKind(indexType, TypeFlags.TypeVariable | TypeFlags.Index) || isGenericMappedType(objectType)) {
+                if (objectType.flags & TypeFlags.Any) {
+                    return objectType;
+                }
                 // If the index type is generic or if the object type is a mapped type with a generic constraint,
                 // we are performing a higher-order index access where we cannot meaningfully access the properties
                 // of the object type. In those cases, we first check that the index type is assignable to 'keyof T'

diff --git a/tests/baselines/reference/keyofAndIndexedAccess.js b/tests/baselines/reference/keyofAndIndexedAccess.js
@@ -353,6 +353,17 @@ interface Options2<Data, Computed> {
 declare class Component2<Data, Computed> {
     constructor(options: Options2<Data, Computed>);
     get<K extends keyof Data | keyof Computed>(key: K): (Data & Computed)[K];
+}
+
+// Repro from #12641
+
+interface R {
+    p: number;
+}
+
+function f<K extends keyof R>(p: K) {
+    let a: any;
+    a[p].add;  // any
 }
 
 //// [keyofAndIndexedAccess.js]
@@ -589,6 +600,10 @@ var c1 = new Component1({
     }
 });
 c1.get("hello");
+function f(p) {
+    var a;
+    a[p].add; // any
+}
 
 
 //// [keyofAndIndexedAccess.d.ts]
@@ -757,3 +772,7 @@ declare class Component2<Data, Computed> {
     constructor(options: Options2<Data, Computed>);
     get<K extends keyof Data | keyof Computed>(key: K): (Data & Computed)[K];
 }
+interface R {
+    p: number;
+}
+declare function f<K extends keyof R>(p: K): void;
diff --git a/tests/baselines/reference/keyofAndIndexedAccess.symbols b/tests/baselines/reference/keyofAndIndexedAccess.symbols
@@ -1320,3 +1320,27 @@ declare class Component2<Data, Computed> {
 >Computed : Symbol(Computed, Decl(keyofAndIndexedAccess.ts, 351, 30))
 >K : Symbol(K, Decl(keyofAndIndexedAccess.ts, 353, 8))
 }
+
+// Repro from #12641
+
+interface R {
+>R : Symbol(R, Decl(keyofAndIndexedAccess.ts, 354, 1))
+
+    p: number;
+>p : Symbol(R.p, Decl(keyofAndIndexedAccess.ts, 358, 13))
+}
+
+function f<K extends keyof R>(p: K) {
+>f : Symbol(f, Decl(keyofAndIndexedAccess.ts, 360, 1))
+>K : Symbol(K, Decl(keyofAndIndexedAccess.ts, 362, 11))
+>R : Symbol(R, Decl(keyofAndIndexedAccess.ts, 354, 1))
+>p : Symbol(p, Decl(keyofAndIndexedAccess.ts, 362, 30))
+>K : Symbol(K, Decl(keyofAndIndexedAccess.ts, 362, 11))
+
+    let a: any;
+>a : Symbol(a, Decl(keyofAndIndexedAccess.ts, 363, 7))
+
+    a[p].add;  // any
+>a : Symbol(a, Decl(keyofAndIndexedAccess.ts, 363, 7))
+>p : Symbol(p, Decl(keyofAndIndexedAccess.ts, 362, 30))
+}
diff --git a/tests/baselines/reference/keyofAndIndexedAccess.types b/tests/baselines/reference/keyofAndIndexedAccess.types
@@ -1560,3 +1560,30 @@ declare class Component2<Data, Computed> {
 >Computed : Computed
 >K : K
 }
+
+// Repro from #12641
+
+interface R {
+>R : R
+
+    p: number;
+>p : number
+}
+
+function f<K extends keyof R>(p: K) {
+>f : <K extends "p">(p: K) => void
+>K : K
+>R : R
+>p : K
+>K : K
+
+    let a: any;
+>a : any
+
+    a[p].add;  // any
+>a[p].add : any
+>a[p] : any
+>a : any
+>p : K
+>add : any
+}
diff --git a/tests/cases/conformance/types/keyof/keyofAndIndexedAccess.ts b/tests/cases/conformance/types/keyof/keyofAndIndexedAccess.ts
@@ -354,4 +354,15 @@ interface Options2<Data, Computed> {
 declare class Component2<Data, Computed> {
     constructor(options: Options2<Data, Computed>);
     get<K extends keyof Data | keyof Computed>(key: K): (Data & Computed)[K];
+}
+
+// Repro from #12641
+
+interface R {
+    p: number;
+}
+
+function f<K extends keyof R>(p: K) {
+    let a: any;
+    a[p].add;  // any
 }