Allow const in for statements

src/compiler/diagnosticInformationMap.generated.ts

@@ -116,8 +116,8 @@ module ts {
         new_T_cannot_be_used_to_create_an_array_Use_new_Array_T_instead: { code: 1150, category: DiagnosticCategory.Error, key: "'new T[]' cannot be used to create an array. Use 'new Array<T>()' instead." },
         An_enum_member_cannot_have_a_numeric_name: { code: 1151, category: DiagnosticCategory.Error, key: "An enum member cannot have a numeric name." },
         var_let_or_const_expected: { code: 1152, category: DiagnosticCategory.Error, key: "'var', 'let' or 'const' expected." },
-        let_variable_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher: { code: 1153, category: DiagnosticCategory.Error, key: "'let' variable declarations are only available when targeting ECMAScript 6 and higher." },
-        const_variable_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher: { code: 1154, category: DiagnosticCategory.Error, key: "'const' variable declarations are only available when targeting ECMAScript 6 and higher." },
+        let_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher: { code: 1153, category: DiagnosticCategory.Error, key: "'let' declarations are only available when targeting ECMAScript 6 and higher." },
+        const_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher: { code: 1154, category: DiagnosticCategory.Error, key: "'const' declarations are only available when targeting ECMAScript 6 and higher." },
         const_must_be_intialized: { code: 1155, category: DiagnosticCategory.Error, key: "const must be intialized." },
         const_must_be_declared_inside_a_block: { code: 1156, category: DiagnosticCategory.Error, key: "const must be declared inside a block." },
         let_must_be_declared_inside_a_block: { code: 1157, category: DiagnosticCategory.Error, key: "let must be declared inside a block." },

src/compiler/diagnosticMessages.json

@@ -455,11 +455,11 @@
         "category": "Error",
         "code": 1152
     },
-    "'let' variable declarations are only available when targeting ECMAScript 6 and higher.": {
+    "'let' declarations are only available when targeting ECMAScript 6 and higher.": {
         "category": "Error",
         "code": 1153
     },
-    "'const' variable declarations are only available when targeting ECMAScript 6 and higher.": {
+    "'const' declarations are only available when targeting ECMAScript 6 and higher.": {
         "category": "Error",
         "code": 1154
     },

src/compiler/parser.ts

@@ -2654,7 +2654,16 @@ module ts {
                         error(Diagnostics.Variable_declaration_list_cannot_be_empty);
                     }
                     if (languageVersion < ScriptTarget.ES6) {
-                        grammarErrorAtPos(declarations.pos, declarations.end - declarations.pos, Diagnostics.let_variable_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher);
+                        grammarErrorAtPos(declarations.pos, declarations.end - declarations.pos, Diagnostics.let_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher);
+                    }
+                }
+                else if (parseOptional(SyntaxKind.ConstKeyword)) {
+                    var declarations = parseVariableDeclarationList(NodeFlags.Const, true);
+                    if (!declarations.length) {
+                        error(Diagnostics.Variable_declaration_list_cannot_be_empty);
+                    }
+                    if (languageVersion < ScriptTarget.ES6) {
+                        grammarErrorAtPos(declarations.pos, declarations.end - declarations.pos, Diagnostics.const_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher);
                     }
                 }
                 else {
@@ -3145,10 +3154,10 @@ module ts {
             }
             if (languageVersion < ScriptTarget.ES6) {
                 if (node.flags & NodeFlags.Let) {
-                    grammarErrorOnNode(node, Diagnostics.let_variable_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher);
+                    grammarErrorOnNode(node, Diagnostics.let_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher);
                 }
                 else if (node.flags & NodeFlags.Const) {
-                    grammarErrorOnNode(node, Diagnostics.const_variable_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher);
+                    grammarErrorOnNode(node, Diagnostics.const_declarations_are_only_available_when_targeting_ECMAScript_6_and_higher);
                 }
             }
             else if (!allowLetDeclarations){

tests/baselines/reference/constDeclarations-errors.errors.txt

@@ -4,20 +4,13 @@ tests/cases/compiler/constDeclarations-errors.ts(5,7): error TS1155: const must
 tests/cases/compiler/constDeclarations-errors.ts(5,11): error TS1155: const must be intialized.
 tests/cases/compiler/constDeclarations-errors.ts(5,15): error TS1155: const must be intialized.
 tests/cases/compiler/constDeclarations-errors.ts(5,27): error TS1155: const must be intialized.
-tests/cases/compiler/constDeclarations-errors.ts(8,5): error TS1109: Expression expected.
-tests/cases/compiler/constDeclarations-errors.ts(8,5): error TS1156: const must be declared inside a block.
 tests/cases/compiler/constDeclarations-errors.ts(8,11): error TS1155: const must be intialized.
-tests/cases/compiler/constDeclarations-errors.ts(8,13): error TS1005: ';' expected.
-tests/cases/compiler/constDeclarations-errors.ts(8,13): error TS1128: Declaration or statement expected.
-tests/cases/compiler/constDeclarations-errors.ts(8,18): error TS1128: Declaration or statement expected.
-tests/cases/compiler/constDeclarations-errors.ts(10,5): error TS1109: Expression expected.
-tests/cases/compiler/constDeclarations-errors.ts(10,5): error TS1156: const must be declared inside a block.
-tests/cases/compiler/constDeclarations-errors.ts(10,28): error TS1005: ';' expected.
-tests/cases/compiler/constDeclarations-errors.ts(10,18): error TS2304: Cannot find name 'c'.
-tests/cases/compiler/constDeclarations-errors.ts(10,25): error TS2304: Cannot find name 'c'.
+tests/cases/compiler/constDeclarations-errors.ts(14,11): error TS1155: const must be intialized.
+tests/cases/compiler/constDeclarations-errors.ts(17,20): error TS1155: const must be intialized.
+tests/cases/compiler/constDeclarations-errors.ts(11,27): error TS2449: The operand of an increment or decrement operator cannot be a constant.
 
 
-==== tests/cases/compiler/constDeclarations-errors.ts (17 errors) ====
+==== tests/cases/compiler/constDeclarations-errors.ts (10 errors) ====
 
     // error, missing intialicer
     const c1;
@@ -36,30 +29,22 @@ tests/cases/compiler/constDeclarations-errors.ts(10,25): error TS2304: Cannot fi
                               ~~
 !!! error TS1155: const must be intialized.
 
-    // error, wrong context
+    // error, can not be unintalized
     for(const c in {}) { }
-        ~~~~~
-!!! error TS1109: Expression expected.
-        ~~~~~~~
-!!! error TS1156: const must be declared inside a block.
               ~
 !!! error TS1155: const must be intialized.
-                ~~
-!!! error TS1005: ';' expected.
-                ~~
-!!! error TS1128: Declaration or statement expected.
-                     ~
-!!! error TS1128: Declaration or statement expected.
 
-    for(const c = 0; c < 9; c++) { }
-        ~~~~~
-!!! error TS1109: Expression expected.
-        ~~~~~~~~~~~~
-!!! error TS1156: const must be declared inside a block.
-                               ~
-!!! error TS1005: ';' expected.
-                     ~
-!!! error TS2304: Cannot find name 'c'.
-                            ~
-!!! error TS2304: Cannot find name 'c'.
-
+    // error, assigning to a const
+    for(const c8 = 0; c8 < 1; c8++) { }
+                              ~~
+!!! error TS2449: The operand of an increment or decrement operator cannot be a constant.
+
+    // error, can not be unintalized
+    for(const c9; c9 < 1;) { }
+              ~~
+!!! error TS1155: const must be intialized.
+
+    // error, can not be unintalized
+    for(const c10 = 0, c11; c10 < 1;) { }
+                       ~~~
+!!! error TS1155: const must be intialized.

tests/baselines/reference/constDeclarations-es5.errors.txt

@@ -1,17 +1,17 @@
-tests/cases/compiler/constDeclarations-es5.ts(2,1): error TS1154: 'const' variable declarations are only available when targeting ECMAScript 6 and higher.
-tests/cases/compiler/constDeclarations-es5.ts(3,1): error TS1154: 'const' variable declarations are only available when targeting ECMAScript 6 and higher.
-tests/cases/compiler/constDeclarations-es5.ts(4,1): error TS1154: 'const' variable declarations are only available when targeting ECMAScript 6 and higher.
+tests/cases/compiler/constDeclarations-es5.ts(2,1): error TS1154: 'const' declarations are only available when targeting ECMAScript 6 and higher.
+tests/cases/compiler/constDeclarations-es5.ts(3,1): error TS1154: 'const' declarations are only available when targeting ECMAScript 6 and higher.
+tests/cases/compiler/constDeclarations-es5.ts(4,1): error TS1154: 'const' declarations are only available when targeting ECMAScript 6 and higher.
 
 
 ==== tests/cases/compiler/constDeclarations-es5.ts (3 errors) ====
 
     const z7 = false;
     ~~~~~~~~~~~~~~~~~
-!!! error TS1154: 'const' variable declarations are only available when targeting ECMAScript 6 and higher.
+!!! error TS1154: 'const' declarations are only available when targeting ECMAScript 6 and higher.
     const z8: number = 23;
     ~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS1154: 'const' variable declarations are only available when targeting ECMAScript 6 and higher.
+!!! error TS1154: 'const' declarations are only available when targeting ECMAScript 6 and higher.
     const z9 = 0, z10 :string = "", z11 = null;
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS1154: 'const' variable declarations are only available when targeting ECMAScript 6 and higher.
+!!! error TS1154: 'const' declarations are only available when targeting ECMAScript 6 and higher.
 

tests/baselines/reference/constDeclarations-scopes2.js

@@ -0,0 +1,27 @@
+//// [constDeclarations-scopes2.ts]
+
+// global
+const c = "string";
+
+var n: number;
+var b: boolean;
+
+// for scope
+for (const c = 0; c < 10; n = c ) {
+    // for block
+    const c = false;
+    b = c;
+}
+
+
+
+//// [constDeclarations-scopes2.js]
+// global
+const c = "string";
+var n;
+var b;
+for (var c = 0; c < 10; n = c) {
+    // for block
+    const c = false;
+    b = c;
+}

tests/baselines/reference/constDeclarations-scopes2.types

@@ -0,0 +1,32 @@
+=== tests/cases/compiler/constDeclarations-scopes2.ts ===
+
+// global
+const c = "string";
+>c : string
+
+var n: number;
+>n : number
+
+var b: boolean;
+>b : boolean
+
+// for scope
+for (const c = 0; c < 10; n = c ) {
+>c : number
+>c < 10 : boolean
+>c : number
+>n = c : number
+>n : number
+>c : number
+
+    // for block
+    const c = false;
+>c : boolean
+
+    b = c;
+>b = c : boolean
+>b : boolean
+>c : boolean
+}
+
+

tests/baselines/reference/constDeclarations.js

@@ -4,13 +4,24 @@
 const c1 = false;
 const c2: number = 23;
 const c3 = 0, c4 :string = "", c5 = null;
-
+
+
+for(const c4 = 0; c4 < 9; ) { break; }
+
+
+for(const c5 = 0, c6 = 0; c5 < c6; ) { break; }
 
 //// [constDeclarations.js]
 // No error
 const c1 = false;
 const c2 = 23;
 const c3 = 0, c4 = "", c5 = null;
+for (var c4 = 0; c4 < 9;) {
+    break;
+}
+for (var c5 = 0, c6 = 0; c5 < c6;) {
+    break;
+}
 
 
 //// [constDeclarations.d.ts]

tests/baselines/reference/constDeclarations.types

@@ -12,3 +12,17 @@ const c3 = 0, c4 :string = "", c5 = null;
 >c4 : string
 >c5 : any
 
+
+for(const c4 = 0; c4 < 9; ) { break; }
+>c4 : number
+>c4 < 9 : boolean
+>c4 : number
+
+
+for(const c5 = 0, c6 = 0; c5 < c6; ) { break; }
+>c5 : number
+>c6 : number
+>c5 < c6 : boolean
+>c5 : number
+>c6 : number
+

tests/cases/compiler/constDeclarations-errors.ts

@@ -5,7 +5,14 @@ const c1;
 const c2: number;
 const c3, c4, c5 :string, c6;  // error, missing initialicer
 
-// error, wrong context
+// error, can not be unintalized
 for(const c in {}) { }
 
-for(const c = 0; c < 9; c++) { }
+// error, assigning to a const
+for(const c8 = 0; c8 < 1; c8++) { }
+
+// error, can not be unintalized
+for(const c9; c9 < 1;) { }
+
+// error, can not be unintalized
+for(const c10 = 0, c11; c10 < 1;) { }

tests/cases/compiler/constDeclarations-scopes2.ts

@@ -0,0 +1,15 @@
+// @target: ES6
+
+// global
+const c = "string";
+
+var n: number;
+var b: boolean;
+
+// for scope
+for (const c = 0; c < 10; n = c ) {
+    // for block
+    const c = false;
+    b = c;
+}
+

tests/cases/compiler/constDeclarations.ts

@@ -5,3 +5,9 @@
 const c1 = false;
 const c2: number = 23;
 const c3 = 0, c4 :string = "", c5 = null;
+
+
+for(const c4 = 0; c4 < 9; ) { break; }
+
+
+for(const c5 = 0, c6 = 0; c5 < c6; ) { break; }