Ensure '{ [key]: x } = obj' for generic key is the same as 'x = obj[key]'

Author: ahejlsberg

src/compiler/checker.ts

@@ -4667,12 +4667,8 @@ namespace ts {
                 else {
                     // Use explicitly specified property name ({ p: xxx } form), or otherwise the implied name ({ p } form)
                     const name = declaration.propertyName || <Identifier>declaration.name;
-                    const exprType = isComputedPropertyName(name)
-                        ? checkComputedPropertyName(name)
-                        : isIdentifier(name)
-                            ? getLiteralType(unescapeLeadingUnderscores(name.escapedText))
-                            : checkExpression(name);
-                    const declaredType = checkIndexedAccessIndexType(getIndexedAccessType(getApparentType(parentType), exprType, name), name);
+                    const exprType = getLiteralTypeFromPropertyName(name);
+                    const declaredType = checkIndexedAccessIndexType(getIndexedAccessType(parentType, exprType, name), name);
                     type = getFlowTypeOfReference(declaration, getConstraintForLocation(declaredType, declaration.name));
                 }
             }
@@ -9528,7 +9524,7 @@ namespace ts {
             // object type. Note that for a generic T and a non-generic K, we eagerly resolve T[K] if it originates in
             // an expression. This is to preserve backwards compatibility. For example, an element access 'this["foo"]'
             // has always been resolved eagerly using the constraint type of 'this' at the given location.
-            if (isGenericIndexType(indexType) || !(accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression) && isGenericObjectType(objectType)) {
+            if (isGenericIndexType(indexType) || !(accessNode && accessNode.kind !== SyntaxKind.IndexedAccessType) && isGenericObjectType(objectType)) {
                 if (objectType.flags & TypeFlags.AnyOrUnknown) {
                     return objectType;
                 }