support case when variable is re-assigned

src/services/refactors/convertStringOrTemplateLiteral.ts

@@ -83,8 +83,12 @@ namespace ts.refactor.convertStringOrTemplateLiteral {
         return text.length === 0 ? [expression] : [expression, createStringLiteral(text)];
     }
 
+    function isNotEqualsOperator(node: BinaryExpression) {
+        return node.operatorToken.kind !== SyntaxKind.EqualsToken;
+    }
+
     function getParentBinaryExpression(expr: Node) {
-        while (isBinaryExpression(expr.parent)) {
+        while (isBinaryExpression(expr.parent) && isNotEqualsOperator(expr.parent)) {
             expr = expr.parent;
         }
         return expr;

tests/cases/fourslash/refactorConvertStringOrTemplateLiteral_ToTemplateAvailabilityReassignment.ts

@@ -0,0 +1,16 @@
+/// <reference path='fourslash.ts' />
+
+//// let foo = ""
+//// /*z*/f/*y*/oo = "/*x*/M/*w*/r Bar" + " is" + /*v*/4/*u*/2 + " years old"
+
+goTo.select("z", "y");
+verify.not.refactorAvailable("Convert string concatenation or template literal", "Convert to string concatenation");
+verify.not.refactorAvailable("Convert string concatenation or template literal", "Convert to template literal");
+
+goTo.select("x", "w");
+verify.not.refactorAvailable("Convert string concatenation or template literal", "Convert to string concatenation");
+verify.refactorAvailable("Convert string concatenation or template literal", "Convert to template literal");
+
+goTo.select("v", "u");
+verify.not.refactorAvailable("Convert string concatenation or template literal", "Convert to string concatenation");
+verify.refactorAvailable("Convert string concatenation or template literal", "Convert to template literal");

tests/cases/fourslash/refactorConvertStringOrTemplateLiteral_ToTemplateDollar.ts

@@ -10,3 +10,4 @@ edit.applyRefactor({
     newContent:
 "const foo = `with $\\\\{dollar}`",
 });
+