Improve more error messages

Author: ahejlsberg

src/compiler/checker.ts

@@ -13614,7 +13614,7 @@ namespace ts {
                     if (ok) {
                         // run check only if former checks succeeded to avoid reporting cascading errors
                         checkReferenceExpression(node.operand,
-                            Diagnostics.The_operand_of_an_increment_or_decrement_operator_must_be_a_variable_property_or_indexer,
+                            Diagnostics.The_operand_of_an_increment_or_decrement_operator_must_be_a_variable_or_a_property_access,
                             Diagnostics.The_operand_of_an_increment_or_decrement_operator_cannot_be_a_constant_or_a_read_only_property);
                     }
                     return numberType;
@@ -13632,7 +13632,7 @@ namespace ts {
             if (ok) {
                 // run check only if former checks succeeded to avoid reporting cascading errors
                 checkReferenceExpression(node.operand,
-                    Diagnostics.The_operand_of_an_increment_or_decrement_operator_must_be_a_variable_property_or_indexer,
+                    Diagnostics.The_operand_of_an_increment_or_decrement_operator_must_be_a_variable_or_a_property_access,
                     Diagnostics.The_operand_of_an_increment_or_decrement_operator_cannot_be_a_constant_or_a_read_only_property);
             }
             return numberType;
@@ -13859,7 +13859,7 @@ namespace ts {
 
         function checkReferenceAssignment(target: Expression, sourceType: Type, contextualMapper?: TypeMapper): Type {
             const targetType = checkExpression(target, contextualMapper);
-            if (checkReferenceExpression(target, Diagnostics.Invalid_left_hand_side_of_assignment_expression, Diagnostics.Left_hand_side_of_assignment_expression_cannot_be_a_constant_or_a_read_only_property)) {
+            if (checkReferenceExpression(target, Diagnostics.The_left_hand_side_of_an_assignment_expression_must_be_a_variable_or_a_property_access, Diagnostics.Left_hand_side_of_assignment_expression_cannot_be_a_constant_or_a_read_only_property)) {
                 checkTypeAssignableTo(sourceType, targetType, target, /*headMessage*/ undefined);
             }
             return sourceType;
@@ -14143,7 +14143,7 @@ namespace ts {
                     // A compound assignment furthermore requires VarExpr to be classified as a reference (section 4.1)
                     // and the type of the non - compound operation to be assignable to the type of VarExpr.
                     const ok = checkReferenceExpression(left,
-                        Diagnostics.Invalid_left_hand_side_of_assignment_expression,
+                        Diagnostics.The_left_hand_side_of_an_assignment_expression_must_be_a_variable_or_a_property_access,
                         Diagnostics.Left_hand_side_of_assignment_expression_cannot_be_a_constant_or_a_read_only_property);
                     // Use default messages
                     if (ok) {
@@ -16588,7 +16588,7 @@ namespace ts {
                 }
                 else {
                     const leftType = checkExpression(varExpr);
-                    checkReferenceExpression(varExpr, /*invalidReferenceMessage*/ Diagnostics.Invalid_left_hand_side_in_for_of_statement,
+                    checkReferenceExpression(varExpr, /*invalidReferenceMessage*/ Diagnostics.The_left_hand_side_of_a_for_of_statement_must_be_a_variable_or_a_property_access,
                         /*constantVariableMessage*/ Diagnostics.The_left_hand_side_of_a_for_of_statement_cannot_be_a_constant_or_a_read_only_property);
 
                     // iteratedType will be undefined if the rightType was missing properties/signatures
@@ -16639,7 +16639,7 @@ namespace ts {
                 }
                 else {
                     // run check only former check succeeded to avoid cascading errors
-                    checkReferenceExpression(varExpr, Diagnostics.Invalid_left_hand_side_in_for_in_statement,
+                    checkReferenceExpression(varExpr, Diagnostics.The_left_hand_side_of_a_for_in_statement_must_be_a_variable_or_a_property_access,
                         Diagnostics.The_left_hand_side_of_a_for_in_statement_cannot_be_a_constant_or_a_read_only_property);
                 }
             }

src/compiler/diagnosticMessages.json

@@ -1075,7 +1075,7 @@
         "category": "Error",
         "code": 2356
     },
-    "The operand of an increment or decrement operator must be a variable, property or indexer.": {
+    "The operand of an increment or decrement operator must be a variable or a property access.": {
         "category": "Error",
         "code": 2357
     },
@@ -1103,7 +1103,7 @@
         "category": "Error",
         "code": 2363
     },
-    "Invalid left-hand side of assignment expression.": {
+    "The left-hand side of an assignment expression must be a variable or a property access.": {
         "category": "Error",
         "code": 2364
     },
@@ -1263,7 +1263,7 @@
         "category": "Error",
         "code": 2405
     },
-    "Invalid left-hand side in 'for...in' statement.": {
+    "The left-hand side of a 'for...in' statement must be a variable or a property access.": {
         "category": "Error",
         "code": 2406
     },
@@ -1563,7 +1563,7 @@
         "category": "Error",
         "code": 2486
     },
-    "Invalid left-hand side in 'for...of' statement.": {
+    "The left-hand side of a 'for...of' statement must be a variable or a property access.": {
         "category": "Error",
         "code": 2487
     },
@@ -1771,6 +1771,10 @@
         "category": "Error",
         "code": 2540
     },
+    "The target of an assignment must be a variable or a property access.": {
+        "category": "Error",
+        "code": 2541
+    },
     "JSX element attributes type '{0}' may not be a union type.": {
         "category": "Error",
         "code": 2600