Add string fallback for number

Author: weswigham

src/compiler/checker.ts

@@ -4176,7 +4176,7 @@ namespace ts {
                         const exprType = checkExpression((name as ComputedPropertyName).expression);
                         let indexerType: Type;
                         if (isTypeAssignableToKind(exprType, TypeFlags.NumberLike)) {
-                            indexerType = getIndexTypeOfType(parentType, IndexKind.Number);
+                            indexerType = getIndexTypeOfType(parentType, IndexKind.Number) || getIndexTypeOfType(parentType, IndexKind.String);
                         }
                         else if (isTypeAssignableToKind(exprType, TypeFlags.StringLike)) {
                             indexerType = getIndexTypeOfType(parentType, IndexKind.String);

tests/baselines/reference/lateBoundDestructuringImplicitAnyError.errors.txt

@@ -1,9 +1,8 @@
 tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(2,15): error TS7017: Element implicitly has an 'any' type because type '{ prop: string; }' has no index signature.
 tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(10,15): error TS7015: Element implicitly has an 'any' type because index expression is not of type 'number'.
-tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(16,15): error TS7017: Element implicitly has an 'any' type because type '{ [idx: string]: string; }' has no index signature.
 
 
-==== tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts (3 errors) ====
+==== tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts (2 errors) ====
     let named = "foo";
     let {[named]: prop} = {prop: "foo"};
                   ~~~~
@@ -24,7 +23,5 @@ tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(16,15): error TS7
     let {[named]: prop4} = strIndexed;
     void prop4;
     let {[numed]: prop5} = strIndexed;
-                  ~~~~~
-!!! error TS7017: Element implicitly has an 'any' type because type '{ [idx: string]: string; }' has no index signature.
     void prop5;
 

tests/baselines/reference/lateBoundDestructuringImplicitAnyError.types

@@ -59,10 +59,10 @@ void prop4;
 
 let {[numed]: prop5} = strIndexed;
 >numed : number
->prop5 : any
+>prop5 : string
 >strIndexed : { [idx: string]: string; }
 
 void prop5;
 >void prop5 : undefined
->prop5 : any
+>prop5 : string