Ensure enum members syntactically determinable to be strings do not get reverse mappings

src/compiler/transformers/ts.ts

@@ -122,6 +122,7 @@ import {
     isSimpleInlineableExpression,
     isSourceFile,
     isStatement,
+    isSyntacticallyString,
     isTemplateLiteral,
     isTryStatement,
     JsxOpeningElement,
@@ -1922,7 +1923,7 @@ export function transformTypeScript(context: TransformationContext) {
             ),
             valueExpression,
         );
-        const outerAssignment = valueExpression.kind === SyntaxKind.StringLiteral ?
+        const outerAssignment = isSyntacticallyString(valueExpression) ?
             innerAssignment :
             factory.createAssignment(
                 factory.createElementAccessExpression(

src/compiler/utilities.ts

@@ -10639,3 +10639,23 @@ export function replaceFirstStar(s: string, replacement: string): string {
 export function getNameFromImportAttribute(node: ImportAttribute) {
     return isIdentifier(node.name) ? node.name.escapedText : escapeLeadingUnderscores(node.name.text);
 }
+
+/** @internal */
+export function isSyntacticallyString(expr: Expression): boolean {
+    switch (expr.kind) {
+        case SyntaxKind.BinaryExpression:
+            const left = (expr as BinaryExpression).left;
+            const right = (expr as BinaryExpression).right;
+            return (
+                (expr as BinaryExpression).operatorToken.kind === SyntaxKind.PlusToken &&
+                (isSyntacticallyString(left) || isSyntacticallyString(right))
+            );
+        case SyntaxKind.ParenthesizedExpression:
+            return isSyntacticallyString((expr as ParenthesizedExpression).expression);
+        case SyntaxKind.TemplateExpression:
+        case SyntaxKind.StringLiteral:
+        case SyntaxKind.NoSubstitutionTemplateLiteral:
+            return true;
+    }
+    return false;
+}

src/testRunner/unittests/services/transpile.ts

@@ -673,4 +673,13 @@ export * as alias from './file';`,
             options: { compilerOptions: { module: ts.ModuleKind.ESNext, target: ts.ScriptTarget.ESNext } },
         },
     );
+
+    transpilesCorrectly(
+        "Syntactically string but non-evaluatable enum members do not get reverse mapping",
+        // eslint-disable-next-line no-template-curly-in-string
+        "import { BAR } from './bar'; enum Foo { A = `${BAR}` }",
+        {
+            options: { compilerOptions: { target: ts.ScriptTarget.ESNext } },
+        },
+    );
 });

tests/baselines/reference/computedEnumMemberSyntacticallyString(isolatedmodules=false).errors.txt

@@ -0,0 +1,16 @@
+computedEnumMemberSyntacticallyString.ts(4,9): error TS18033: Type 'string' is not assignable to type 'number' as required for computed enum member values.
+computedEnumMemberSyntacticallyString.ts(5,9): error TS18033: Type 'string' is not assignable to type 'number' as required for computed enum member values.
+
+
+==== computedEnumMemberSyntacticallyString.ts (2 errors) ====
+    const BAR = 2..toFixed(0);
+
+    enum Foo {
+        A = `${BAR}`,
+            ~~~~~~~~
+!!! error TS18033: Type 'string' is not assignable to type 'number' as required for computed enum member values.
+        B = "2" + BAR,
+            ~~~~~~~~~
+!!! error TS18033: Type 'string' is not assignable to type 'number' as required for computed enum member values.
+    }
+

tests/baselines/reference/computedEnumMemberSyntacticallyString(isolatedmodules=false).js

@@ -0,0 +1,18 @@
+//// [tests/cases/compiler/computedEnumMemberSyntacticallyString.ts] ////
+
+//// [computedEnumMemberSyntacticallyString.ts]
+const BAR = 2..toFixed(0);
+
+enum Foo {
+    A = `${BAR}`,
+    B = "2" + BAR,
+}
+
+
+//// [computedEnumMemberSyntacticallyString.js]
+const BAR = 2..toFixed(0);
+var Foo;
+(function (Foo) {
+    Foo["A"] = `${BAR}`;
+    Foo["B"] = "2" + BAR;
+})(Foo || (Foo = {}));

tests/baselines/reference/computedEnumMemberSyntacticallyString(isolatedmodules=true).errors.txt

@@ -0,0 +1,16 @@
+computedEnumMemberSyntacticallyString.ts(4,9): error TS18033: Type 'string' is not assignable to type 'number' as required for computed enum member values.
+computedEnumMemberSyntacticallyString.ts(5,9): error TS18033: Type 'string' is not assignable to type 'number' as required for computed enum member values.
+
+
+==== computedEnumMemberSyntacticallyString.ts (2 errors) ====
+    const BAR = 2..toFixed(0);
+
+    enum Foo {
+        A = `${BAR}`,
+            ~~~~~~~~
+!!! error TS18033: Type 'string' is not assignable to type 'number' as required for computed enum member values.
+        B = "2" + BAR,
+            ~~~~~~~~~
+!!! error TS18033: Type 'string' is not assignable to type 'number' as required for computed enum member values.
+    }
+

tests/baselines/reference/computedEnumMemberSyntacticallyString(isolatedmodules=true).js

@@ -0,0 +1,18 @@
+//// [tests/cases/compiler/computedEnumMemberSyntacticallyString.ts] ////
+
+//// [computedEnumMemberSyntacticallyString.ts]
+const BAR = 2..toFixed(0);
+
+enum Foo {
+    A = `${BAR}`,
+    B = "2" + BAR,
+}
+
+
+//// [computedEnumMemberSyntacticallyString.js]
+const BAR = 2..toFixed(0);
+var Foo;
+(function (Foo) {
+    Foo["A"] = `${BAR}`;
+    Foo["B"] = "2" + BAR;
+})(Foo || (Foo = {}));

tests/baselines/reference/computedEnumMemberSyntacticallyString2(isolatedmodules=false).js

@@ -0,0 +1,17 @@
+//// [tests/cases/compiler/computedEnumMemberSyntacticallyString2.ts] ////
+
+//// [foo.ts]
+import { BAR } from './bar';
+enum Foo { A = `${BAR}` }
+
+//// [bar.ts]
+export const BAR = 'bar';
+
+//// [bar.js]
+export const BAR = 'bar';
+//// [foo.js]
+import { BAR } from './bar';
+var Foo;
+(function (Foo) {
+    Foo["A"] = "bar";
+})(Foo || (Foo = {}));

tests/baselines/reference/computedEnumMemberSyntacticallyString2(isolatedmodules=true).js

@@ -0,0 +1,17 @@
+//// [tests/cases/compiler/computedEnumMemberSyntacticallyString2.ts] ////
+
+//// [foo.ts]
+import { BAR } from './bar';
+enum Foo { A = `${BAR}` }
+
+//// [bar.ts]
+export const BAR = 'bar';
+
+//// [bar.js]
+export const BAR = 'bar';
+//// [foo.js]
+import { BAR } from './bar';
+var Foo;
+(function (Foo) {
+    Foo["A"] = "bar";
+})(Foo || (Foo = {}));

tests/cases/compiler/computedEnumMemberSyntacticallyString.ts

@@ -0,0 +1,10 @@
+// @isolatedModules: true,false
+// @noTypesAndSymbols: true
+// @target: esnext
+
+const BAR = 2..toFixed(0);
+
+enum Foo {
+    A = `${BAR}`,
+    B = "2" + BAR,
+}

tests/cases/compiler/computedEnumMemberSyntacticallyString2.ts

@@ -0,0 +1,10 @@
+// @isolatedModules: true,false
+// @noTypesAndSymbols: true
+// @target: esnext
+
+// @filename: ./foo.ts
+import { BAR } from './bar';
+enum Foo { A = `${BAR}` }
+
+// @filename: ./bar.ts
+export const BAR = 'bar';