microsoft · DanielRosenwasser · Aug 6, 2021 · Jul 4, 2021
diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
@@ -2294,7 +2294,7 @@ namespace ts {
             // Provide specialized messages to help the user understand why we think they're in
             // strict mode.
             if (getContainingClass(node)) {
-                return Diagnostics.Invalid_use_of_0_Class_definitions_are_automatically_in_strict_mode;
+                return Diagnostics.Code_contained_in_a_class_is_evaluated_in_JavaScript_s_strict_mode_which_does_not_allow_this_use_of_0_For_more_information_see_https_Colon_Slash_Slashdeveloper_mozilla_org_Slashen_US_Slashdocs_SlashWeb_SlashJavaScript_SlashReference_SlashStrict_mode;
             }
 
             if (file.externalModuleIndicator) {

diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
@@ -663,7 +663,7 @@
         "category": "Error",
         "code": 1208
     },
-    "Invalid use of '{0}'. Class definitions are automatically in strict mode.": {
+    "Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of '{0}'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.": {
         "category": "Error",
         "code": 1210
     },

diff --git a/tests/baselines/reference/classStaticBlock6.errors.txt b/tests/baselines/reference/classStaticBlock6.errors.txt
@@ -1,5 +1,5 @@
-tests/cases/conformance/classes/classStaticBlock/classStaticBlock6.ts(8,13): error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
-tests/cases/conformance/classes/classStaticBlock/classStaticBlock6.ts(9,13): error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+tests/cases/conformance/classes/classStaticBlock/classStaticBlock6.ts(8,13): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
+tests/cases/conformance/classes/classStaticBlock/classStaticBlock6.ts(9,13): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'eval'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
 tests/cases/conformance/classes/classStaticBlock/classStaticBlock6.ts(13,9): error TS18037: Await expression cannot be used inside a class static block.
 tests/cases/conformance/classes/classStaticBlock/classStaticBlock6.ts(13,14): error TS1109: Expression expected.
 tests/cases/conformance/classes/classStaticBlock/classStaticBlock6.ts(17,9): error TS2662: Cannot find name 'arguments'. Did you mean the static member 'C.arguments'?
@@ -25,10 +25,10 @@ tests/cases/conformance/classes/classStaticBlock/classStaticBlock6.ts(55,13): er
             let await = 1;
             let arguments = 1;
                 ~~~~~~~~~
-!!! error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
             let eval = 1;
                 ~~~~
-!!! error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'eval'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
         }
 
         static {

diff --git a/tests/baselines/reference/collisionArgumentsClassConstructor.errors.txt b/tests/baselines/reference/collisionArgumentsClassConstructor.errors.txt
diff --git a/tests/baselines/reference/collisionArgumentsClassMethod.errors.txt b/tests/baselines/reference/collisionArgumentsClassMethod.errors.txt
diff --git a/tests/baselines/reference/emitArrowFunctionWhenUsingArguments12.errors.txt b/tests/baselines/reference/emitArrowFunctionWhenUsingArguments12.errors.txt
@@ -1,12 +1,12 @@
-tests/cases/conformance/es6/arrowFunction/emitArrowFunctionWhenUsingArguments12.ts(2,7): error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+tests/cases/conformance/es6/arrowFunction/emitArrowFunctionWhenUsingArguments12.ts(2,7): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
 tests/cases/conformance/es6/arrowFunction/emitArrowFunctionWhenUsingArguments12.ts(3,23): error TS2496: The 'arguments' object cannot be referenced in an arrow function in ES3 and ES5. Consider using a standard function expression.
 
 
 ==== tests/cases/conformance/es6/arrowFunction/emitArrowFunctionWhenUsingArguments12.ts (2 errors) ====
     class C {
         f(arguments) {
           ~~~~~~~~~
-!!! error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
             var a = () => arguments;
                           ~~~~~~~~~
 !!! error TS2496: The 'arguments' object cannot be referenced in an arrow function in ES3 and ES5. Consider using a standard function expression.

diff --git a/tests/baselines/reference/emitArrowFunctionWhenUsingArguments12_ES6.errors.txt b/tests/baselines/reference/emitArrowFunctionWhenUsingArguments12_ES6.errors.txt
@@ -1,11 +1,11 @@
-tests/cases/conformance/es6/arrowFunction/emitArrowFunctionWhenUsingArguments12_ES6.ts(2,7): error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+tests/cases/conformance/es6/arrowFunction/emitArrowFunctionWhenUsingArguments12_ES6.ts(2,7): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
 
 
 ==== tests/cases/conformance/es6/arrowFunction/emitArrowFunctionWhenUsingArguments12_ES6.ts (1 errors) ====
     class C {
         f(arguments) {
           ~~~~~~~~~
-!!! error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
             var a = () => arguments;
         }
     }
diff --git a/tests/baselines/reference/jsFileCompilationBindStrictModeErrors.errors.txt b/tests/baselines/reference/jsFileCompilationBindStrictModeErrors.errors.txt
@@ -7,7 +7,7 @@ tests/cases/compiler/a.js(10,10): error TS1100: Invalid use of 'eval' in strict
 tests/cases/compiler/a.js(12,10): error TS1100: Invalid use of 'arguments' in strict mode.
 tests/cases/compiler/a.js(15,1): error TS1101: 'with' statements are not allowed in strict mode.
 tests/cases/compiler/a.js(15,1): error TS2410: The 'with' statement is not supported. All symbols in a 'with' block will have type 'any'.
-tests/cases/compiler/b.js(3,7): error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+tests/cases/compiler/b.js(3,7): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'eval'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
 tests/cases/compiler/b.js(6,13): error TS1213: Identifier expected. 'let' is a reserved word in strict mode. Class definitions are automatically in strict mode.
 tests/cases/compiler/c.js(1,12): error TS1214: Identifier expected. 'let' is a reserved word in strict mode. Modules are automatically in strict mode.
 tests/cases/compiler/c.js(2,5): error TS1215: Invalid use of 'eval'. Modules are automatically in strict mode.
@@ -57,7 +57,7 @@ tests/cases/compiler/d.js(2,11): error TS1005: ',' expected.
     class c {
         a(eval) { //error
           ~~~~
-!!! error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'eval'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
         }
         method() {
             var let = 10; // error

diff --git a/tests/baselines/reference/parseClassDeclarationInStrictModeByDefaultInES6.errors.txt b/tests/baselines/reference/parseClassDeclarationInStrictModeByDefaultInES6.errors.txt
@@ -1,6 +1,6 @@
-tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(4,16): error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
-tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(5,17): error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
-tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(6,9): error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(4,16): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
+tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(5,17): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'eval'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
+tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(6,9): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
 tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeByDefaultInES6.ts(6,9): error TS2322: Type 'string' is not assignable to type 'IArguments'.
 
 
@@ -10,13 +10,13 @@ tests/cases/conformance/es6/classDeclaration/parseClassDeclarationInStrictModeBy
         public implements() { }
         public foo(arguments: any) { }
                    ~~~~~~~~~
-!!! error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
         private bar(eval:any) {
                     ~~~~
-!!! error TS1210: Invalid use of 'eval'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'eval'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
             arguments = "hello";
             ~~~~~~~~~
-!!! error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
             ~~~~~~~~~
 !!! error TS2322: Type 'string' is not assignable to type 'IArguments'.
         }

diff --git a/tests/baselines/reference/parserRealSource11.errors.txt b/tests/baselines/reference/parserRealSource11.errors.txt
@@ -113,7 +113,7 @@ tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(504,58): error
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(506,22): error TS2304: Cannot find name 'NodeType'.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(507,58): error TS2304: Cannot find name 'TokenID'.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(518,32): error TS2304: Cannot find name 'NodeType'.
-tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(520,29): error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(520,29): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(525,27): error TS2304: Cannot find name 'Signature'.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(527,36): error TS2304: Cannot find name 'TypeFlow'.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(528,34): error TS2304: Cannot find name 'NodeType'.
@@ -241,7 +241,7 @@ tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(959,27): error
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(961,25): error TS2304: Cannot find name 'IHashTable'.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(963,27): error TS2304: Cannot find name 'Signature'.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(981,27): error TS2304: Cannot find name 'Type'.
-tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(985,29): error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(985,29): error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(1004,44): error TS2304: Cannot find name 'hasFlag'.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(1004,67): error TS2304: Cannot find name 'FncFlags'.
 tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(1005,57): error TS2304: Cannot find name 'FncFlags'.
@@ -1263,7 +1263,7 @@ tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(2356,48): error
                          public target: AST,
                          public arguments: ASTList) {
                                 ~~~~~~~~~
-!!! error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
                 super(nodeType);
                 this.minChar = this.target.minChar;
             }
@@ -1984,7 +1984,7 @@ tests/cases/conformance/parser/ecmascript5/parserRealSource11.ts(2356,48): error
             constructor (public name: Identifier, public bod: ASTList, public isConstructor: boolean,
                          public arguments: ASTList, public vars: ASTList, public scopes: ASTList, public statics: ASTList,
                                 ~~~~~~~~~
-!!! error TS1210: Invalid use of 'arguments'. Class definitions are automatically in strict mode.
+!!! error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'arguments'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.
                 nodeType: number) {
 
                 super(nodeType);