Error handling test

src/compiler/checker.ts

@@ -40405,6 +40405,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 setLastResult(state, checkDestructuringAssignment(node.left, checkExpression(node.right, checkMode), checkMode, node.right.kind === SyntaxKind.ThisKeyword));
                 return state;
             }
+            else if (isStringLiteral(node.left) && isStringLiteral(node.right) && operator !== SyntaxKind.EqualsToken) {
+                error(node, Diagnostics.Comparison_of_string_literals_is_not_allowed);
+            }
 
             return state;
         }

src/compiler/diagnosticMessages.json

@@ -8519,5 +8519,9 @@
     "'{0}' is not a valid meta-property for keyword 'import'. Did you mean 'meta' or 'defer'?": {
         "category": "Error",
         "code": 18061
+    },
+    "Comparison of string literals is not allowed.": {
+        "category": "Error",
+        "code": 18062
     }
 }

tests/baselines/reference/stringComp.js

@@ -0,0 +1,6 @@
+//// [tests/cases/compiler/stringComp.ts] ////
+
+//// [stringComp.ts]
+
+
+//// [stringComp.js]

tests/baselines/reference/stringComp.symbols

@@ -0,0 +1,4 @@
+//// [tests/cases/compiler/stringComp.ts] ////
+
+=== stringComp.ts ===
+

tests/baselines/reference/stringComp.types

@@ -0,0 +1,4 @@
+//// [tests/cases/compiler/stringComp.ts] ////
+
+=== stringComp.ts ===
+

tests/cases/compiler/StringComp.ts

@@ -0,0 +1,3 @@
+if ("bar" <= "foo") {
+  console.log("Really?")
+}