add new error message 'Cannot assign to {0} because it is a constant.'

src/compiler/checker.ts

@@ -15891,7 +15891,12 @@ namespace ts {
                     return errorType;
                 }
                 if (isReadonlySymbol(localOrExportSymbol)) {
-                    error(node, Diagnostics.Cannot_assign_to_0_because_it_is_a_constant_or_a_read_only_property, symbolToString(symbol));
+                    if (localOrExportSymbol.flags & SymbolFlags.Variable) {
+                        error(node, Diagnostics.Cannot_assign_to_0_because_it_is_a_constant, symbolToString(symbol));
+                    }
+                    else {
+                        error(node, Diagnostics.Cannot_assign_to_0_because_it_is_a_constant_or_a_read_only_property, symbolToString(symbol));
+                    }
                     return errorType;
                 }
             }

src/compiler/diagnosticMessages.json

@@ -2124,6 +2124,10 @@
         "category": "Error",
         "code": 2587
     },
+    "Cannot assign to '{0}' because it is a constant.": {
+        "category": "Error",
+        "code": 2588
+    },
     "JSX element attributes type '{0}' may not be a union type.": {
         "category": "Error",
         "code": 2600