diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 3b3d4256fecfc..0bd0cfdec45a1 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -26474,6 +26474,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     const key = getFlowCacheKey((node as AccessExpression).expression, declaredType, initialType, flowContainer);
                     return key && key + "." + propName;
                 }
+                else if (isElementAccessExpression(node) && isConstantReference(node.argumentExpression)) {
+                    const propertyCacheKey = getFlowCacheKey(node.argumentExpression, unknownType, unknownType, flowContainer);
+                    if (!propertyCacheKey) {
+                        return undefined;
+                    }
+                    const key = getFlowCacheKey((node as AccessExpression).expression, declaredType, initialType, flowContainer);
+                    return key && key + "[" + propertyCacheKey + "]";
+                }
                 break;
             case SyntaxKind.ObjectBindingPattern:
             case SyntaxKind.ArrayBindingPattern:
@@ -26519,8 +26527,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             case SyntaxKind.ElementAccessExpression:
                 const sourcePropertyName = getAccessedPropertyName(source as AccessExpression);
                 const targetPropertyName = isAccessExpression(target) ? getAccessedPropertyName(target) : undefined;
-                return sourcePropertyName !== undefined && targetPropertyName !== undefined && targetPropertyName === sourcePropertyName &&
-                    isMatchingReference((source as AccessExpression).expression, (target as AccessExpression).expression);
+                if (sourcePropertyName !== undefined || targetPropertyName !== undefined) {
+                    return sourcePropertyName !== undefined && targetPropertyName !== undefined && targetPropertyName === sourcePropertyName &&
+                        isMatchingReference((source as AccessExpression).expression, (target as AccessExpression).expression);
+                }
+                else {
+                    return isElementAccessExpression(source) && isElementAccessExpression(target) && isMatchingReference(source.expression, target.expression) &&
+                        isMatchingReference(source.argumentExpression, target.argumentExpression) && isConstantReference(source.argumentExpression) && isConstantReference(target.argumentExpression);
+                }
             case SyntaxKind.QualifiedName:
                 return isAccessExpression(target) &&
                     (source as QualifiedName).right.escapedText === getAccessedPropertyName(target) &&
diff --git a/tests/baselines/reference/mappedTypeGenericIndexedAccess.types b/tests/baselines/reference/mappedTypeGenericIndexedAccess.types
index 75dd61b90a26e..cb4107f6d38a3 100644
--- a/tests/baselines/reference/mappedTypeGenericIndexedAccess.types
+++ b/tests/baselines/reference/mappedTypeGenericIndexedAccess.types
@@ -60,14 +60,14 @@ class Test {
 >[] : never[]
         }
         this.entries[name]?.push(entry);
->this.entries[name]?.push(entry) : number | undefined
->this.entries[name]?.push : ((...items: Types[T][]) => number) | undefined
->this.entries[name] : Types[T][] | undefined
+>this.entries[name]?.push(entry) : number
+>this.entries[name]?.push : (...items: Types[T][]) => number
+>this.entries[name] : Types[T][]
 >this.entries : { first?: { a1: true; }[] | undefined; second?: { a2: true; }[] | undefined; third?: { a3: true; }[] | undefined; }
 >this : this
 >entries : { first?: { a1: true; }[] | undefined; second?: { a2: true; }[] | undefined; third?: { a3: true; }[] | undefined; }
 >name : T
->push : ((...items: Types[T][]) => number) | undefined
+>push : (...items: Types[T][]) => number
 >entry : Types[T]
     }
 }
diff --git a/tests/baselines/reference/noUncheckedIndexedAccess.errors.txt b/tests/baselines/reference/noUncheckedIndexedAccess.errors.txt
index 5e3da68cf77f1..1199c0dbb17d1 100644
--- a/tests/baselines/reference/noUncheckedIndexedAccess.errors.txt
+++ b/tests/baselines/reference/noUncheckedIndexedAccess.errors.txt
@@ -33,8 +33,7 @@ noUncheckedIndexedAccess.ts(90,7): error TS2322: Type 'string | undefined' is no
   Type 'undefined' is not assignable to type 'string'.
 noUncheckedIndexedAccess.ts(98,5): error TS2322: Type 'undefined' is not assignable to type '{ [key: string]: string; a: string; b: string; }[Key]'.
   Type 'undefined' is not assignable to type 'string'.
-noUncheckedIndexedAccess.ts(99,11): error TS2322: Type 'string | undefined' is not assignable to type 'string'.
-  Type 'undefined' is not assignable to type 'string'.
+noUncheckedIndexedAccess.ts(99,11): error TS2322: Type 'undefined' is not assignable to type 'string'.
 
 
 ==== noUncheckedIndexedAccess.ts (31 errors) ====
@@ -203,8 +202,7 @@ noUncheckedIndexedAccess.ts(99,11): error TS2322: Type 'string | undefined' is n
 !!! error TS2322:   Type 'undefined' is not assignable to type 'string'.
         const v: string = myRecord2[key]; // Should error
               ~
-!!! error TS2322: Type 'string | undefined' is not assignable to type 'string'.
-!!! error TS2322:   Type 'undefined' is not assignable to type 'string'.
+!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
     };
     
     
\ No newline at end of file
diff --git a/tests/baselines/reference/noUncheckedIndexedAccess.types b/tests/baselines/reference/noUncheckedIndexedAccess.types
index 54fad592dfc87..c6fffb01a5f50 100644
--- a/tests/baselines/reference/noUncheckedIndexedAccess.types
+++ b/tests/baselines/reference/noUncheckedIndexedAccess.types
@@ -412,7 +412,7 @@ const fn3 = <Key extends keyof typeof myRecord2>(key: Key) => {
 
     const v: string = myRecord2[key]; // Should error
 >v : string
->myRecord2[key] : string | undefined
+>myRecord2[key] : undefined
 >myRecord2 : { [key: string]: string; a: string; b: string; }
 >key : Key
 
diff --git a/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.errors.txt b/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.errors.txt
new file mode 100644
index 0000000000000..972cbd25a36a7
--- /dev/null
+++ b/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.errors.txt
@@ -0,0 +1,62 @@
+typeGuardNarrowsIndexedAccessOfAnyProperty.ts(51,7): error TS2532: Object is possibly 'undefined'.
+
+
+==== typeGuardNarrowsIndexedAccessOfAnyProperty.ts (1 errors) ====
+    namespace Problem1 {
+      declare const obj: { [key: string]: string | undefined };
+      declare let key: "a";
+      if (obj[key]) { obj[key].toUpperCase() } // should Ok
+    }
+    
+    namespace Problem2 {
+      declare const obj: { [key: string]: string | undefined };
+      declare const key: string;
+      if (obj[key]) { obj[key].toUpperCase() } // should Ok
+    }
+    
+    namespace Problem3 {
+      declare const obj: { a?: string, b?: string };
+      declare const key: "a" | "b";
+      if (obj[key]) { obj[key].toUpperCase() } // should Ok
+    }
+    
+    namespace Problem4 {
+      function f<K extends string>(obj: { [P in K]?: string }, k: K) {
+        const key: K = k;
+        if (obj[key]) { obj[key].toUpperCase() } // should Ok
+      }
+    }
+    
+    namespace Problem5 {
+      declare const obj: { [key: string]: string | undefined };
+      declare const key: string;
+      if (obj[key]) {
+        while(!!true) {
+          obj[key].toUpperCase() // should Ok
+        }
+      } 
+    }
+    
+    namespace Problem6 {
+      declare const obj: { [key: string]: string | undefined };
+      declare const key: string;
+      while(!!true) {
+        if (obj[key]) {
+          obj[key].toUpperCase() // should Ok
+        } 
+      }
+    }
+    
+    namespace Problem7 {
+      declare const obj: { [key: string]: string | undefined };
+      declare const key: string;
+      if (obj[key]) {
+        while(!!true) {
+          obj[key].toUpperCase() // should error
+          ~~~~~~~~
+!!! error TS2532: Object is possibly 'undefined'.
+          obj[key] = undefined
+        }
+      } 
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.js b/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.js
new file mode 100644
index 0000000000000..6a87a2612d55b
--- /dev/null
+++ b/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.js
@@ -0,0 +1,114 @@
+//// [tests/cases/compiler/typeGuardNarrowsIndexedAccessOfAnyProperty.ts] ////
+
+//// [typeGuardNarrowsIndexedAccessOfAnyProperty.ts]
+namespace Problem1 {
+  declare const obj: { [key: string]: string | undefined };
+  declare let key: "a";
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+}
+
+namespace Problem2 {
+  declare const obj: { [key: string]: string | undefined };
+  declare const key: string;
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+}
+
+namespace Problem3 {
+  declare const obj: { a?: string, b?: string };
+  declare const key: "a" | "b";
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+}
+
+namespace Problem4 {
+  function f<K extends string>(obj: { [P in K]?: string }, k: K) {
+    const key: K = k;
+    if (obj[key]) { obj[key].toUpperCase() } // should Ok
+  }
+}
+
+namespace Problem5 {
+  declare const obj: { [key: string]: string | undefined };
+  declare const key: string;
+  if (obj[key]) {
+    while(!!true) {
+      obj[key].toUpperCase() // should Ok
+    }
+  } 
+}
+
+namespace Problem6 {
+  declare const obj: { [key: string]: string | undefined };
+  declare const key: string;
+  while(!!true) {
+    if (obj[key]) {
+      obj[key].toUpperCase() // should Ok
+    } 
+  }
+}
+
+namespace Problem7 {
+  declare const obj: { [key: string]: string | undefined };
+  declare const key: string;
+  if (obj[key]) {
+    while(!!true) {
+      obj[key].toUpperCase() // should error
+      obj[key] = undefined
+    }
+  } 
+}
+
+
+//// [typeGuardNarrowsIndexedAccessOfAnyProperty.js]
+"use strict";
+var Problem1;
+(function (Problem1) {
+    if (obj[key]) {
+        obj[key].toUpperCase();
+    } // should Ok
+})(Problem1 || (Problem1 = {}));
+var Problem2;
+(function (Problem2) {
+    if (obj[key]) {
+        obj[key].toUpperCase();
+    } // should Ok
+})(Problem2 || (Problem2 = {}));
+var Problem3;
+(function (Problem3) {
+    if (obj[key]) {
+        obj[key].toUpperCase();
+    } // should Ok
+})(Problem3 || (Problem3 = {}));
+var Problem4;
+(function (Problem4) {
+    function f(obj, k) {
+        var key = k;
+        if (obj[key]) {
+            obj[key].toUpperCase();
+        } // should Ok
+    }
+})(Problem4 || (Problem4 = {}));
+var Problem5;
+(function (Problem5) {
+    if (obj[key]) {
+        while (!!true) {
+            obj[key].toUpperCase(); // should Ok
+        }
+    }
+})(Problem5 || (Problem5 = {}));
+var Problem6;
+(function (Problem6) {
+    while (!!true) {
+        if (obj[key]) {
+            obj[key].toUpperCase(); // should Ok
+        }
+    }
+})(Problem6 || (Problem6 = {}));
+var Problem7;
+(function (Problem7) {
+    if (obj[key]) {
+        while (!!true) {
+            obj[key].toUpperCase(); // should error
+            obj[key] = undefined;
+        }
+    }
+})(Problem7 || (Problem7 = {}));
diff --git a/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.symbols b/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.symbols
new file mode 100644
index 0000000000000..e25a76e0223be
--- /dev/null
+++ b/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.symbols
@@ -0,0 +1,165 @@
+//// [tests/cases/compiler/typeGuardNarrowsIndexedAccessOfAnyProperty.ts] ////
+
+=== typeGuardNarrowsIndexedAccessOfAnyProperty.ts ===
+namespace Problem1 {
+>Problem1 : Symbol(Problem1, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 0, 0))
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 1, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 1, 24))
+
+  declare let key: "a";
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 2, 13))
+
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 1, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 2, 13))
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 1, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 2, 13))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+}
+
+namespace Problem2 {
+>Problem2 : Symbol(Problem2, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 4, 1))
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 7, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 7, 24))
+
+  declare const key: string;
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 8, 15))
+
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 7, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 8, 15))
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 7, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 8, 15))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+}
+
+namespace Problem3 {
+>Problem3 : Symbol(Problem3, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 10, 1))
+
+  declare const obj: { a?: string, b?: string };
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 13, 15))
+>a : Symbol(a, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 13, 22))
+>b : Symbol(b, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 13, 34))
+
+  declare const key: "a" | "b";
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 14, 15))
+
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 13, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 14, 15))
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 13, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 14, 15))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+}
+
+namespace Problem4 {
+>Problem4 : Symbol(Problem4, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 16, 1))
+
+  function f<K extends string>(obj: { [P in K]?: string }, k: K) {
+>f : Symbol(f, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 18, 20))
+>K : Symbol(K, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 13))
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 31))
+>P : Symbol(P, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 39))
+>K : Symbol(K, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 13))
+>k : Symbol(k, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 58))
+>K : Symbol(K, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 13))
+
+    const key: K = k;
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 20, 9))
+>K : Symbol(K, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 13))
+>k : Symbol(k, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 58))
+
+    if (obj[key]) { obj[key].toUpperCase() } // should Ok
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 31))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 20, 9))
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 19, 31))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 20, 9))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+  }
+}
+
+namespace Problem5 {
+>Problem5 : Symbol(Problem5, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 23, 1))
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 26, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 26, 24))
+
+  declare const key: string;
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 27, 15))
+
+  if (obj[key]) {
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 26, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 27, 15))
+
+    while(!!true) {
+      obj[key].toUpperCase() // should Ok
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 26, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 27, 15))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+    }
+  } 
+}
+
+namespace Problem6 {
+>Problem6 : Symbol(Problem6, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 33, 1))
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 36, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 36, 24))
+
+  declare const key: string;
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 37, 15))
+
+  while(!!true) {
+    if (obj[key]) {
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 36, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 37, 15))
+
+      obj[key].toUpperCase() // should Ok
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 36, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 37, 15))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+    } 
+  }
+}
+
+namespace Problem7 {
+>Problem7 : Symbol(Problem7, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 43, 1))
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 46, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 46, 24))
+
+  declare const key: string;
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 47, 15))
+
+  if (obj[key]) {
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 46, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 47, 15))
+
+    while(!!true) {
+      obj[key].toUpperCase() // should error
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 46, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 47, 15))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+
+      obj[key] = undefined
+>obj : Symbol(obj, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 46, 15))
+>key : Symbol(key, Decl(typeGuardNarrowsIndexedAccessOfAnyProperty.ts, 47, 15))
+>undefined : Symbol(undefined)
+    }
+  } 
+}
+
diff --git a/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.types b/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.types
new file mode 100644
index 0000000000000..907ba3a5851b1
--- /dev/null
+++ b/tests/baselines/reference/typeGuardNarrowsIndexedAccessOfAnyProperty.types
@@ -0,0 +1,195 @@
+//// [tests/cases/compiler/typeGuardNarrowsIndexedAccessOfAnyProperty.ts] ////
+
+=== typeGuardNarrowsIndexedAccessOfAnyProperty.ts ===
+namespace Problem1 {
+>Problem1 : typeof Problem1
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : { [key: string]: string | undefined; }
+>key : string
+
+  declare let key: "a";
+>key : "a"
+
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+>obj[key] : string | undefined
+>obj : { [key: string]: string | undefined; }
+>key : "a"
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : { [key: string]: string | undefined; }
+>key : "a"
+>toUpperCase : () => string
+}
+
+namespace Problem2 {
+>Problem2 : typeof Problem2
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : { [key: string]: string | undefined; }
+>key : string
+
+  declare const key: string;
+>key : string
+
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+>obj[key] : string | undefined
+>obj : { [key: string]: string | undefined; }
+>key : string
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : { [key: string]: string | undefined; }
+>key : string
+>toUpperCase : () => string
+}
+
+namespace Problem3 {
+>Problem3 : typeof Problem3
+
+  declare const obj: { a?: string, b?: string };
+>obj : { a?: string | undefined; b?: string | undefined; }
+>a : string | undefined
+>b : string | undefined
+
+  declare const key: "a" | "b";
+>key : "a" | "b"
+
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+>obj[key] : string | undefined
+>obj : { a?: string | undefined; b?: string | undefined; }
+>key : "a" | "b"
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : { a?: string | undefined; b?: string | undefined; }
+>key : "a" | "b"
+>toUpperCase : () => string
+}
+
+namespace Problem4 {
+>Problem4 : typeof Problem4
+
+  function f<K extends string>(obj: { [P in K]?: string }, k: K) {
+>f : <K extends string>(obj: { [P in K]?: string | undefined; }, k: K) => void
+>obj : { [P in K]?: string | undefined; }
+>k : K
+
+    const key: K = k;
+>key : K
+>k : K
+
+    if (obj[key]) { obj[key].toUpperCase() } // should Ok
+>obj[key] : { [P in K]?: string | undefined; }[K]
+>obj : { [P in K]?: string | undefined; }
+>key : K
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : { [P in K]?: string | undefined; }
+>key : K
+>toUpperCase : () => string
+  }
+}
+
+namespace Problem5 {
+>Problem5 : typeof Problem5
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : { [key: string]: string | undefined; }
+>key : string
+
+  declare const key: string;
+>key : string
+
+  if (obj[key]) {
+>obj[key] : string | undefined
+>obj : { [key: string]: string | undefined; }
+>key : string
+
+    while(!!true) {
+>!!true : true
+>!true : false
+>true : true
+
+      obj[key].toUpperCase() // should Ok
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : { [key: string]: string | undefined; }
+>key : string
+>toUpperCase : () => string
+    }
+  } 
+}
+
+namespace Problem6 {
+>Problem6 : typeof Problem6
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : { [key: string]: string | undefined; }
+>key : string
+
+  declare const key: string;
+>key : string
+
+  while(!!true) {
+>!!true : true
+>!true : false
+>true : true
+
+    if (obj[key]) {
+>obj[key] : string | undefined
+>obj : { [key: string]: string | undefined; }
+>key : string
+
+      obj[key].toUpperCase() // should Ok
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : { [key: string]: string | undefined; }
+>key : string
+>toUpperCase : () => string
+    } 
+  }
+}
+
+namespace Problem7 {
+>Problem7 : typeof Problem7
+
+  declare const obj: { [key: string]: string | undefined };
+>obj : { [key: string]: string | undefined; }
+>key : string
+
+  declare const key: string;
+>key : string
+
+  if (obj[key]) {
+>obj[key] : string | undefined
+>obj : { [key: string]: string | undefined; }
+>key : string
+
+    while(!!true) {
+>!!true : true
+>!true : false
+>true : true
+
+      obj[key].toUpperCase() // should error
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string | undefined
+>obj : { [key: string]: string | undefined; }
+>key : string
+>toUpperCase : () => string
+
+      obj[key] = undefined
+>obj[key] = undefined : undefined
+>obj[key] : string | undefined
+>obj : { [key: string]: string | undefined; }
+>key : string
+>undefined : undefined
+    }
+  } 
+}
+
diff --git a/tests/cases/compiler/typeGuardNarrowsIndexedAccessOfAnyProperty.ts b/tests/cases/compiler/typeGuardNarrowsIndexedAccessOfAnyProperty.ts
new file mode 100644
index 0000000000000..d88d491a4e601
--- /dev/null
+++ b/tests/cases/compiler/typeGuardNarrowsIndexedAccessOfAnyProperty.ts
@@ -0,0 +1,56 @@
+// @strict: true
+namespace Problem1 {
+  declare const obj: { [key: string]: string | undefined };
+  declare let key: "a";
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+}
+
+namespace Problem2 {
+  declare const obj: { [key: string]: string | undefined };
+  declare const key: string;
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+}
+
+namespace Problem3 {
+  declare const obj: { a?: string, b?: string };
+  declare const key: "a" | "b";
+  if (obj[key]) { obj[key].toUpperCase() } // should Ok
+}
+
+namespace Problem4 {
+  function f<K extends string>(obj: { [P in K]?: string }, k: K) {
+    const key: K = k;
+    if (obj[key]) { obj[key].toUpperCase() } // should Ok
+  }
+}
+
+namespace Problem5 {
+  declare const obj: { [key: string]: string | undefined };
+  declare const key: string;
+  if (obj[key]) {
+    while(!!true) {
+      obj[key].toUpperCase() // should Ok
+    }
+  } 
+}
+
+namespace Problem6 {
+  declare const obj: { [key: string]: string | undefined };
+  declare const key: string;
+  while(!!true) {
+    if (obj[key]) {
+      obj[key].toUpperCase() // should Ok
+    } 
+  }
+}
+
+namespace Problem7 {
+  declare const obj: { [key: string]: string | undefined };
+  declare const key: string;
+  if (obj[key]) {
+    while(!!true) {
+      obj[key].toUpperCase() // should error
+      obj[key] = undefined
+    }
+  } 
+}