recommend set if el is on RHS of assignment else get

Author: collin5

src/compiler/checker.ts

@@ -9285,9 +9285,9 @@ namespace ts {
                                 }
                             }
                             else {
-                                const suggestions = getSuggestionsForNonexistentIndexSignature(objectType);
-                                if (suggestions) {
-                                    error(accessExpression, Diagnostics.Element_implicitly_has_an_any_type_because_type_0_has_no_index_signature_Did_you_mean_to_call_1, typeToString(objectType), suggestions);
+                                const suggestion = getSuggestionForNonexistentIndexSignature(objectType, accessExpression);
+                                if (suggestion) {
+                                    error(accessExpression, Diagnostics.Element_implicitly_has_an_any_type_because_type_0_has_no_index_signature_Did_you_mean_to_call_1, typeToString(objectType), suggestion);
                                 }
                                 else {
                                     error(accessExpression, Diagnostics.Element_implicitly_has_an_any_type_because_type_0_has_no_index_signature, typeToString(objectType));
@@ -18455,23 +18455,32 @@ namespace ts {
             return suggestion && symbolName(suggestion);
         }
 
-        function getSuggestionsForNonexistentIndexSignature(objectType: Type): string | undefined {
-            let suggestions: string | undefined;
-            const props = [
-                getPropertyOfObjectType(objectType, <__String>"get"),
-                getPropertyOfObjectType(objectType, <__String>"set")
-            ];
-
-            for (const prop of props) {
+        function getSuggestionForNonexistentIndexSignature(objectType: Type, expr: ElementAccessExpression): string | undefined {
+            let suggestion: string | undefined;
+            // check if object type has setter or getter
+            const hasProp = (name: "set" | "get") => {
+                const prop = getPropertyOfObjectType(objectType, <__String>name);
                 if (prop) {
                     const s = getSingleCallSignature(getTypeOfSymbol(prop));
                     if (s && getMinArgumentCount(s) === 1 && typeToString(getTypeAtPosition(s, 0)) === "string") {
-                        const suggestion = symbolToString(objectType.symbol) + "." + symbolToString(prop);
-                        suggestions = (!suggestions) ? suggestion : suggestions.concat(" or " + suggestion);
+                        return true;
                     }
                 }
+                return false;
+            };
+
+            if (isAssignmentTarget(expr)) {
+                if (hasProp("set")) {
+                    suggestion = symbolToString(objectType.symbol) + ".set";
+                }
             }
-            return suggestions;
+            else {
+                if (hasProp("get")) {
+                    suggestion = symbolToString(objectType.symbol) + ".get";
+                }
+            }
+
+            return suggestion;
         }
 
         /**