Disallow line terminator after arrow function parameters, before =>

src/compiler/checker.ts

@@ -448,7 +448,7 @@ module ts {
             let declaration = forEach(result.declarations, d => isBlockOrCatchScoped(d) ? d : undefined);
 
             Debug.assert(declaration !== undefined, "Block-scoped variable declaration is undefined");
-                    
+
             // first check if usage is lexically located after the declaration
             let isUsedBeforeDeclaration = !isDefinedBefore(declaration, errorLocation);
             if (!isUsedBeforeDeclaration) {
@@ -465,7 +465,7 @@ module ts {
 
                 if (variableDeclaration.parent.parent.kind === SyntaxKind.VariableStatement ||
                     variableDeclaration.parent.parent.kind === SyntaxKind.ForStatement) {
-                    // variable statement/for statement case, 
+                    // variable statement/for statement case,
                     // use site should not be inside variable declaration (initializer of declaration or binding element)
                     isUsedBeforeDeclaration = isSameScopeDescendentOf(errorLocation, variableDeclaration, container);
                 }
@@ -4412,7 +4412,7 @@ module ts {
         }
 
         /**
-         * Check if a Type was written as a tuple type literal. 
+         * Check if a Type was written as a tuple type literal.
          * Prefer using isTupleLikeType() unless the use of `elementTypes` is required.
          */
         function isTupleType(type: Type) : boolean {
@@ -9080,7 +9080,7 @@ module ts {
          */
         function checkElementTypeOfArrayOrString(arrayOrStringType: Type, expressionForError: Expression): Type {
             Debug.assert(languageVersion < ScriptTarget.ES6);
-            
+
             // After we remove all types that are StringLike, we will know if there was a string constituent
             // based on whether the remaining type is the same as the initial type.
             let arrayType = removeTypesFromUnionType(arrayOrStringType, TypeFlags.StringLike, /*isTypeOfKind*/ true, /*allowEmptyUnionResult*/ true);
@@ -11324,16 +11324,15 @@ module ts {
             }
         }
 
-        function checkGrammarTypeParameterList(node: FunctionLikeDeclaration, typeParameters: NodeArray<TypeParameterDeclaration>): boolean {
+        function checkGrammarTypeParameterList(node: FunctionLikeDeclaration, typeParameters: NodeArray<TypeParameterDeclaration>, file: SourceFile): boolean {
             if (checkGrammarForDisallowedTrailingComma(typeParameters)) {
                 return true;
             }
 
             if (typeParameters && typeParameters.length === 0) {
                 let start = typeParameters.pos - "<".length;
-                let sourceFile = getSourceFileOfNode(node);
-                let end = skipTrivia(sourceFile.text, typeParameters.end) + ">".length;
-                return grammarErrorAtPos(sourceFile, start, end - start, Diagnostics.Type_parameter_list_cannot_be_empty);
+                let end = skipTrivia(file.text, typeParameters.end) + ">".length;
+                return grammarErrorAtPos(file, start, end - start, Diagnostics.Type_parameter_list_cannot_be_empty);
             }
         }
 
@@ -11377,7 +11376,21 @@ module ts {
 
         function checkGrammarFunctionLikeDeclaration(node: FunctionLikeDeclaration): boolean {
             // Prevent cascading error by short-circuit
-            return checkGrammarModifiers(node) || checkGrammarTypeParameterList(node, node.typeParameters) || checkGrammarParameterList(node.parameters);
+            let file = getSourceFileOfNode(node);
+            return checkGrammarModifiers(node) || checkGrammarTypeParameterList(node, node.typeParameters, file) ||
+                checkGrammarParameterList(node.parameters) || checkGrammarArrowFunction(node, file);
+        }
+
+        function checkGrammarArrowFunction(node: FunctionLikeDeclaration, file: SourceFile): boolean {
+            if (node.kind === SyntaxKind.ArrowFunction) {
+                let arrowFunction = <ArrowFunction>node;
+                let startLine = getLineAndCharacterOfPosition(file, arrowFunction.equalsGreaterThanToken.pos).line;
+                let endLine = getLineAndCharacterOfPosition(file, arrowFunction.equalsGreaterThanToken.end).line;
+                if (startLine !== endLine) {
+                    return grammarErrorOnNode(arrowFunction.equalsGreaterThanToken, Diagnostics.Line_terminator_not_permitted_before_arrow);
+                }
+            }
+            return false;
         }
 
         function checkGrammarIndexSignatureParameters(node: SignatureDeclaration): boolean {

src/compiler/diagnosticInformationMap.generated.ts

@@ -157,6 +157,7 @@ module ts {
         Catch_clause_variable_cannot_have_an_initializer: { code: 1197, category: DiagnosticCategory.Error, key: "Catch clause variable cannot have an initializer." },
         An_extended_Unicode_escape_value_must_be_between_0x0_and_0x10FFFF_inclusive: { code: 1198, category: DiagnosticCategory.Error, key: "An extended Unicode escape value must be between 0x0 and 0x10FFFF inclusive." },
         Unterminated_Unicode_escape_sequence: { code: 1199, category: DiagnosticCategory.Error, key: "Unterminated Unicode escape sequence." },
+        Line_terminator_not_permitted_before_arrow: { code: 1200, category: DiagnosticCategory.Error, key: "Line terminator not permitted before arrow." },
         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." },

src/compiler/diagnosticMessages.json

@@ -619,6 +619,10 @@
         "category": "Error",
         "code":  1199
     },
+    "Line terminator not permitted before arrow.": {
+        "category": "Error",
+        "code": 1200
+    },
     "Duplicate identifier '{0}'.": {
         "category": "Error",
         "code": 2300