Better check for right.text, more comments in test

Author: mihailik

src/compiler/checker.ts

@@ -15929,12 +15929,16 @@ namespace ts {
                     checkAssignmentOperator(rightType);
                     return getRegularTypeOfObjectLiteral(rightType);
                 case SyntaxKind.CommaToken:
-                    if (!compilerOptions.allowUnreachableCode && isSideEffectFree(left) && right.text!=="eval") {
+                    if (!compilerOptions.allowUnreachableCode && isSideEffectFree(left) && !isEvalNode(right)) {
                         error(left, Diagnostics.Left_side_of_comma_operator_is_unused_and_has_no_side_effects);
                     }
                     return rightType;
             }
 
+            function isEvalNode(node: Expression) {
+                return node.kind === SyntaxKind.Identifier && (node as Identifier).text === "eval";
+            }
+
             // Return true if there was no error, false if there was an error.
             function checkForDisallowedESSymbolOperand(operator: SyntaxKind): boolean {
                 const offendingSymbolOperand =

tests/cases/compiler/evalAfter0.ts

@@ -1,3 +1,3 @@
-(0,eval)("10");
+(0,eval)("10"); // fine: special case for eval
 
-(0,alert)("10");
+(0,alert)("10"); // error: no side effect left of comma (suspect of missing method name or something)