Avoid convertExport when there's a non-identifier or a bogus one

Fixes microsoft#44105

Author: elibarzilay

src/compiler/diagnosticMessages.json

@@ -6397,6 +6397,10 @@
         "category": "Message",
         "code": 95163
     },
+    "Can only convert named export": {
+        "category": "Message",
+        "code": 95164
+    },
 
     "No value exists in scope for the shorthand property '{0}'. Either declare one or provide an initializer.": {
         "category": "Error",

src/services/refactors/convertExport.ts

@@ -57,7 +57,7 @@ namespace ts.refactor {
     };
 
     function getInfo(context: RefactorContext, considerPartialSpans = true): ExportInfo | RefactorErrorInfo | undefined {
-        const { file } = context;
+        const { file, program } = context;
         const span = getRefactorContextSpan(context);
         const token = getTokenAtPosition(file, span.start);
         const exportNode = !!(token.parent && getSyntacticModifierFlags(token.parent) & ModifierFlags.Export) && considerPartialSpans ? token.parent : getParentNodeInSpan(token, file, span);
@@ -75,6 +75,11 @@ namespace ts.refactor {
             return { error: getLocaleSpecificMessage(Diagnostics.This_file_already_has_a_default_export) };
         }
 
+        const checker = program.getTypeChecker();
+        const noSymbolError = (id: Node) =>
+            (isIdentifier(id) && checker.getSymbolAtLocation(id)) ? undefined
+            : { error: getLocaleSpecificMessage(Diagnostics.Can_only_convert_named_export) };
+
         switch (exportNode.kind) {
             case SyntaxKind.FunctionDeclaration:
             case SyntaxKind.ClassDeclaration:
@@ -83,7 +88,9 @@ namespace ts.refactor {
             case SyntaxKind.TypeAliasDeclaration:
             case SyntaxKind.ModuleDeclaration: {
                 const node = exportNode as FunctionDeclaration | ClassDeclaration | InterfaceDeclaration | EnumDeclaration | TypeAliasDeclaration | NamespaceDeclaration;
-                return node.name && isIdentifier(node.name) ? { exportNode: node, exportName: node.name, wasDefault, exportingModuleSymbol } : undefined;
+                if (!node.name) return undefined;
+                return noSymbolError(node.name)
+                    || { exportNode: node, exportName: node.name, wasDefault, exportingModuleSymbol };
             }
             case SyntaxKind.VariableStatement: {
                 const vs = exportNode as VariableStatement;
@@ -94,12 +101,14 @@ namespace ts.refactor {
                 const decl = first(vs.declarationList.declarations);
                 if (!decl.initializer) return undefined;
                 Debug.assert(!wasDefault, "Can't have a default flag here");
-                return isIdentifier(decl.name) ? { exportNode: vs, exportName: decl.name, wasDefault, exportingModuleSymbol } : undefined;
+                return noSymbolError(decl.name)
+                    || { exportNode: vs, exportName: decl.name as Identifier, wasDefault, exportingModuleSymbol };
             }
             case SyntaxKind.ExportAssignment: {
                 const node = exportNode as ExportAssignment;
-                const exp = node.expression as Identifier;
-                return node.isExportEquals ? undefined : { exportNode: node, exportName: exp, wasDefault, exportingModuleSymbol };
+                if (node.isExportEquals) return undefined;
+                return noSymbolError(node.expression)
+                    || { exportNode: node, exportName: node.expression as Identifier, wasDefault, exportingModuleSymbol };
             }
             default:
                 return undefined;

tests/cases/fourslash/refactorConvertExport_onlyValidIdentifiers.ts

@@ -0,0 +1,25 @@
+/// <reference path='fourslash.ts' />
+
+// @allowJs: true
+
+// @Filename: /a.js
+/////*[| |]*/ /** x */ export default 1;
+
+// @Filename: /b.js
+/////*[| |]*/ /** x */ export default (1);
+
+// @Filename: /c.js
+/////*[| |]*/ /** x */ export default x;
+
+goTo.eachRange(r => {
+    goTo.selectRange(r);
+    verify.not.refactorAvailable("Convert export");
+});
+
+// goTo.selectRange(test.ranges()[0]);
+// edit.applyRefactor({
+//     refactorName: "Convert export",
+//     actionName: "Convert default export to named export",
+//     actionDescription: "Convert default export to named export",
+//     newContent: { "/a.js": `...` },
+// });