Add basic parsing support for let and const

microsoft · mhegazy · Oct 24, 2014 · Oct 11, 2014 · Oct 13, 2014 · Oct 13, 2014
commit 778f101dea279a97349261a802158bd1055b77f9
diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
@@ -115,6 +115,10 @@ module ts {
         Filename_0_differs_from_already_included_filename_1_only_in_casing: { code: 1149, category: DiagnosticCategory.Error, key: "Filename '{0}' differs from already included filename '{1}' only in casing" },
         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." },
+        Const_must_be_intialized: { code: 1155, category: DiagnosticCategory.Error, key: "Const must be intialized." },
         Duplicate_identifier_0: { code: 2300, category: DiagnosticCategory.Error, key: "Duplicate identifier '{0}'." },
         Initializer_of_instance_member_variable_0_cannot_reference_identifier_1_declared_in_the_constructor: { code: 2301, category: DiagnosticCategory.Error, key: "Initializer of instance member variable '{0}' cannot reference identifier '{1}' declared in the constructor." },
         Static_members_cannot_reference_class_type_parameters: { code: 2302, category: DiagnosticCategory.Error, key: "Static members cannot reference class type parameters." },

diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
@@ -451,6 +451,22 @@
         "category": "Error",
         "code":  1151
     },
+	"'var', 'let' or 'const' expected.": {
+        "category": "Error",
+        "code": 1152
+    },
+	 "'let' variable 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.": {
+        "category": "Error",
+        "code": 1154
+    },
+	"Const must be intialized.": {
+        "category": "Error",
+        "code": 1155
+    },
 
     "Duplicate identifier '{0}'.": {
         "category": "Error",

diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
@@ -1149,7 +1149,12 @@ module ts {
                 write(" ");
                 endPos = emitToken(SyntaxKind.OpenParenToken, endPos);
                 if (node.declarations) {
-                    emitToken(SyntaxKind.VarKeyword, endPos);
+                    if (node.declarations[0] && node.declarations[0].flags & NodeFlags.Let) {
+                        emitToken(SyntaxKind.LetKeyword, endPos);
+                    }
+                    else {
+                        emitToken(SyntaxKind.VarKeyword, endPos);
+                    }
                     write(" ");
                     emitCommaList(node.declarations, /*includeTrailingComma*/ false);
                 }
@@ -1169,7 +1174,12 @@ module ts {
                 write(" ");
                 endPos = emitToken(SyntaxKind.OpenParenToken, endPos);
                 if (node.declaration) {
-                    emitToken(SyntaxKind.VarKeyword, endPos);
+                    if (node.declaration.flags & NodeFlags.Let) {
+                        emitToken(SyntaxKind.LetKeyword, endPos);
+                    }
+                    else {
+                        emitToken(SyntaxKind.VarKeyword, endPos);
+                    }
                     write(" ");
                     emit(node.declaration);
                 }
@@ -1298,7 +1308,17 @@ module ts {
 
             function emitVariableStatement(node: VariableStatement) {
                 emitLeadingComments(node);
-                if (!(node.flags & NodeFlags.Export)) write("var ");
+                if (!(node.flags & NodeFlags.Export)) {
+                    if (node.flags & NodeFlags.Let) {
+                        write("let ");
+                    }
+                    else if (node.flags & NodeFlags.Const) {
+                        write("const ");
+                    }
+                    else {
+                        write("var ");
+                    }
+                }
                 emitCommaList(node.declarations, /*includeTrailingComma*/ false);
                 write(";");
                 emitTrailingComments(node);
@@ -1774,7 +1794,15 @@ module ts {
                 if (node.flags & NodeFlags.Export) {
                     writeLine();
                     emitStart(node);
-                    write("var ");
+                    if (node.flags & NodeFlags.Let) {
+                        write("let ");
+                    }
+                    else if (node.flags & NodeFlags.Const) {
+                        write("const ");
+                    }
+                    else {
+                        write("var ");
+                    }
                     emit(node.name);
                     write(" = ");
                     emitModuleMemberName(node);
@@ -2822,7 +2850,15 @@ module ts {
                 if (hasDeclarationWithEmit) {
                     emitJsDocComments(node);
                     emitDeclarationFlags(node);
-                    write("var ");
+                    if (node.flags & NodeFlags.Let) {
+                        write("let ");
+                    }
+                    else if (node.flags & NodeFlags.Const) {
+                        write("const ");
+                    }
+                    else {
+                        write("var ");
+                    }
                     emitCommaList(node.declarations, emitVariableDeclaration);
                     write(";");
                     writeLine();

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
@@ -2645,6 +2645,15 @@ module ts {
                         error(Diagnostics.Variable_declaration_list_cannot_be_empty);
                     }
                 }
+                else if (parseOptional(SyntaxKind.LetKeyword)) {
+                    var declarations = parseVariableDeclarationList(NodeFlags.Let, true);
+                    if (!declarations.length) {
+                        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);
+                    }
+                }
                 else {
                     var varOrInit = parseExpression(true);
                 }
@@ -2970,6 +2979,8 @@ module ts {
                     return !inErrorRecovery;
                 case SyntaxKind.OpenBraceToken:
                 case SyntaxKind.VarKeyword:
+                case SyntaxKind.LetKeyword:
+                case SyntaxKind.ConstKeyword:
                 case SyntaxKind.FunctionKeyword:
                 case SyntaxKind.IfKeyword:
                 case SyntaxKind.DoKeyword:
@@ -3016,6 +3027,8 @@ module ts {
                 case SyntaxKind.OpenBraceToken:
                     return parseBlock(/* ignoreMissingOpenBrace */ false, /*checkForStrictMode*/ false);
                 case SyntaxKind.VarKeyword:
+                case SyntaxKind.LetKeyword:
+                case SyntaxKind.ConstKeyword:
                     return parseVariableStatement();
                 case SyntaxKind.FunctionKeyword:
                     return parseFunctionDeclaration();
@@ -3095,6 +3108,9 @@ module ts {
             if (inAmbientContext && node.initializer && errorCountBeforeVariableDeclaration === file.syntacticErrors.length) {
                 grammarErrorAtPos(initializerStart, initializerFirstTokenLength, Diagnostics.Initializers_are_not_allowed_in_ambient_contexts);
             }
+            if (!inAmbientContext && !node.initializer && flags & NodeFlags.Const) {
+                grammarErrorOnNode(node, Diagnostics.Const_must_be_intialized);
+            }
             if (isInStrictMode && isEvalOrArgumentsIdentifier(node.name)) {
                 // It is a SyntaxError if a VariableDeclaration or VariableDeclarationNoIn occurs within strict code 
                 // and its Identifier is eval or arguments 
@@ -3112,13 +3128,30 @@ module ts {
             var node = <VariableStatement>createNode(SyntaxKind.VariableStatement, pos);
             if (flags) node.flags = flags;
             var errorCountBeforeVarStatement = file.syntacticErrors.length;
-            parseExpected(SyntaxKind.VarKeyword);
-            node.declarations = parseVariableDeclarationList(flags, /*noIn*/false);
+            if (token === SyntaxKind.LetKeyword) {
+                node.flags |= NodeFlags.Let;
+            }
+            else if (token === SyntaxKind.ConstKeyword) {
+                node.flags |= NodeFlags.Const;
+            }
+            else if (token !== SyntaxKind.VarKeyword) {
+                error(Diagnostics.var_let_or_const_expected);
+            }
+            nextToken();
+            node.declarations = parseVariableDeclarationList(node.flags, /*noIn*/false);
             parseSemicolon();
             finishNode(node);
             if (!node.declarations.length && file.syntacticErrors.length === errorCountBeforeVarStatement) {
                 grammarErrorOnNode(node, Diagnostics.Variable_declaration_list_cannot_be_empty);
             }
+            if (languageVersion < ScriptTarget.ES6) {
+                if (node.flags & NodeFlags.Let) {
+                    grammarErrorOnNode(node, Diagnostics.let_variable_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);
+                }
+            }
             return node;
         }
 
@@ -3697,6 +3730,8 @@ module ts {
         function isDeclaration(): boolean {
             switch (token) {
                 case SyntaxKind.VarKeyword:
+                case SyntaxKind.LetKeyword:
+                case SyntaxKind.ConstKeyword:
                 case SyntaxKind.FunctionKeyword:
                     return true;
                 case SyntaxKind.ClassKeyword:
@@ -3747,6 +3782,8 @@ module ts {
             var result: Declaration;
             switch (token) {
                 case SyntaxKind.VarKeyword:
+                case SyntaxKind.LetKeyword:
+                case SyntaxKind.ConstKeyword:
                     result = parseVariableStatement(pos, flags);
                     break;
                 case SyntaxKind.FunctionKeyword:

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -245,6 +245,8 @@ module ts {
         MultiLine        = 0x00000100,  // Multi-line array or object literal
         Synthetic        = 0x00000200,  // Synthetic node (for full fidelity)
         DeclarationFile  = 0x00000400,  // Node is a .d.ts file
+        Let              = 0x00000800,
+        Const            = 0x00001000,
 
         Modifier = Export | Ambient | Public | Private | Protected | Static,
         AccessibilityModifier = Public | Private | Protected

diff --git a/tests/baselines/reference/constDeclarations-ambient-errors.errors.txt b/tests/baselines/reference/constDeclarations-ambient-errors.errors.txt
@@ -0,0 +1,34 @@
+tests/cases/compiler/constDeclarations-ambient-errors.ts(3,27): error TS1039: Initializers are not allowed in ambient contexts.
+tests/cases/compiler/constDeclarations-ambient-errors.ts(4,26): error TS1039: Initializers are not allowed in ambient contexts.
+tests/cases/compiler/constDeclarations-ambient-errors.ts(5,18): error TS1039: Initializers are not allowed in ambient contexts.
+tests/cases/compiler/constDeclarations-ambient-errors.ts(5,37): error TS1039: Initializers are not allowed in ambient contexts.
+tests/cases/compiler/constDeclarations-ambient-errors.ts(5,51): error TS1039: Initializers are not allowed in ambient contexts.
+tests/cases/compiler/constDeclarations-ambient-errors.ts(8,14): error TS1039: Initializers are not allowed in ambient contexts.
+tests/cases/compiler/constDeclarations-ambient-errors.ts(9,22): error TS1039: Initializers are not allowed in ambient contexts.
+
+
+==== tests/cases/compiler/constDeclarations-ambient-errors.ts (7 errors) ====
+
+    // error: no intialization expected in ambient declarations
+    declare const c1: boolean = true;
+                              ~
+!!! error TS1039: Initializers are not allowed in ambient contexts.
+    declare const c2: number = 0;
+                             ~
+!!! error TS1039: Initializers are not allowed in ambient contexts.
+    declare const c3 = null, c4 :string = "", c5: any = 0;
+                     ~
+!!! error TS1039: Initializers are not allowed in ambient contexts.
+                                        ~
+!!! error TS1039: Initializers are not allowed in ambient contexts.
+                                                      ~
+!!! error TS1039: Initializers are not allowed in ambient contexts.
+
+    declare module M {
+        const c6 = 0;
+                 ~
+!!! error TS1039: Initializers are not allowed in ambient contexts.
+        const c7: number = 7;
+                         ~
+!!! error TS1039: Initializers are not allowed in ambient contexts.
+    }
diff --git a/tests/baselines/reference/constDeclarations-ambient.js b/tests/baselines/reference/constDeclarations-ambient.js
@@ -0,0 +1,13 @@
+//// [constDeclarations-ambient.ts]
+
+// No error
+declare const c1: boolean;
+declare const c2: number;
+declare const c3, c4 :string, c5: any;
+
+declare module M {
+    const c6;
+    const c7: number;
+}
+
+//// [constDeclarations-ambient.js]
diff --git a/tests/baselines/reference/constDeclarations-ambient.types b/tests/baselines/reference/constDeclarations-ambient.types
@@ -0,0 +1,23 @@
+=== tests/cases/compiler/constDeclarations-ambient.ts ===
+
+// No error
+declare const c1: boolean;
+>c1 : boolean
+
+declare const c2: number;
+>c2 : number
+
+declare const c3, c4 :string, c5: any;
+>c3 : any
+>c4 : string
+>c5 : any
+
+declare module M {
+>M : typeof M
+
+    const c6;
+>c6 : any
+
+    const c7: number;
+>c7 : number
+}
diff --git a/tests/baselines/reference/constDeclarations-errors.errors.txt b/tests/baselines/reference/constDeclarations-errors.errors.txt
@@ -0,0 +1,62 @@
+tests/cases/compiler/constDeclarations-errors.ts(3,7): error TS1155: const must be intialized.
+tests/cases/compiler/constDeclarations-errors.ts(4,7): error TS1155: const must be intialized.
+tests/cases/compiler/constDeclarations-errors.ts(5,7): error TS1155: const must be intialized.
+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(10,11): error TS2403: Subsequent variable declarations must have the same type.  Variable 'c' must be of type 'any', but here has type 'number'.
+
+
+==== tests/cases/compiler/constDeclarations-errors.ts (16 errors) ====
+
+    // error, missing intialicer
+    const c1;
+          ~~
+!!! error TS1155: const must be intialized.
+    const c2: number;
+          ~~
+!!! error TS1155: const must be intialized.
+    const c3, c4, c5 :string, c6;  // error, missing initialicer
+          ~~
+!!! error TS1155: const must be intialized.
+              ~~
+!!! error TS1155: const must be intialized.
+                  ~~
+!!! error TS1155: const must be intialized.
+                              ~~
+!!! error TS1155: const must be intialized.
+
+    // error, wrong context
+    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 TS2403: Subsequent variable declarations must have the same type.  Variable 'c' must be of type 'any', but here has type 'number'.
+
diff --git a/tests/baselines/reference/constDeclarations-es5.errors.txt b/tests/baselines/reference/constDeclarations-es5.errors.txt
@@ -0,0 +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 (3 errors) ====
+
+    const z7 = false;
+    ~~~~~~~~~~~~~~~~~
+!!! error TS1154: 'const' variable 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.
+    const z9 = 0, z10 :string = "", z11 = null;
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS1154: 'const' variable declarations are only available when targeting ECMAScript 6 and higher.
+
diff --git a/tests/baselines/reference/constDeclarations.js b/tests/baselines/reference/constDeclarations.js
@@ -0,0 +1,19 @@
+//// [constDeclarations.ts]
+
+// No error
+const c1 = false;
+const c2: number = 23;
+const c3 = 0, c4 :string = "", c5 = null;
+
+
+//// [constDeclarations.js]
+// No error
+const c1 = false;
+const c2 = 23;
+const c3 = 0, c4 = "", c5 = null;
+
+
+//// [constDeclarations.d.ts]
+declare const c1: boolean;
+declare const c2: number;
+declare const c3: number, c4: string, c5: any;