diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 6c24def150..2471ebcb52 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2610,18 +2610,27 @@ namespace ts {
                     /*initializer*/ undefined);
                 const typeNode = typeToTypeNodeHelper(indexInfo.type);
                 return createIndexSignatureDeclaration(
-                    [indexingParameter],
-                    typeNode,
                     /*decorators*/ undefined,
-                    indexInfo.isReadonly ? [createToken(SyntaxKind.ReadonlyKeyword)] : undefined);
+                    indexInfo.isReadonly ? [createToken(SyntaxKind.ReadonlyKeyword)] : undefined,
+                    [indexingParameter],
+                    typeNode);
             }
 
             function signatureToSignatureDeclarationHelper(signature: Signature, kind: SyntaxKind): SignatureDeclaration {
 
                 const typeParameters = signature.typeParameters && signature.typeParameters.map(parameter => typeParameterToDeclaration(parameter));
                 const parameters = signature.parameters.map(parameter => symbolToParameterDeclaration(parameter));
-                const returnType = getReturnTypeOfSignature(signature);
-                const returnTypeNode = returnType && typeToTypeNodeHelper(returnType);
+                let returnTypeNode: TypeNode | TypePredicate;
+                if (signature.typePredicate) {
+                    const typePredicate = signature.typePredicate;
+                    const parameterName = typePredicate.kind === TypePredicateKind.Identifier ? createIdentifier((<IdentifierTypePredicate>typePredicate).parameterName) : createThisTypeNode();
+                    const typeNode = typeToTypeNodeHelper(typePredicate.type);
+                    returnTypeNode = createTypePredicateNode(parameterName, typeNode);
+                }
+                else {
+                    const returnType = getReturnTypeOfSignature(signature);
+                    returnTypeNode = returnType && typeToTypeNodeHelper(returnType);
+                }
                 const returnTypeNodeExceptAny = returnTypeNode && returnTypeNode.kind !== SyntaxKind.AnyKeyword ? returnTypeNode : undefined;
 
                 return createSignatureDeclaration(kind, typeParameters, parameters, returnTypeNodeExceptAny);
diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index 4c5a4b4067..66b3eb713e 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -286,6 +286,10 @@ namespace ts {
         return <KeywordTypeNode>createSynthesizedNode(kind);
     }
 
+    export function createThisTypeNode() {
+        return <ThisTypeNode>createSynthesizedNode(SyntaxKind.ThisType);
+    }
+
     export function createLiteralTypeNode(literal: Expression) {
         const literalTypeNode = createSynthesizedNode(SyntaxKind.LiteralType) as LiteralTypeNode;
         literalTypeNode.literal = literal;
@@ -312,6 +316,20 @@ namespace ts {
             : node;
     }
 
+    export function createTypePredicateNode(parameterName: Identifier | ThisTypeNode | string, type: TypeNode) {
+        const typePredicateNode = createSynthesizedNode(SyntaxKind.TypePredicate) as TypePredicateNode;
+        typePredicateNode.parameterName = asName(parameterName);
+        typePredicateNode.type = type;
+        return typePredicateNode;
+    }
+
+    export function updateTypePredicateNode(node: TypePredicateNode, parameterName: Identifier | ThisTypeNode, type: TypeNode) {
+        return node.parameterName !== parameterName
+            || node.type !== type
+            ? updateNode(createTypePredicateNode(parameterName, type), node)
+            : node;
+    }
+
     export function createTypeQueryNode(exprName: EntityName) {
         const typeQueryNode = createSynthesizedNode(SyntaxKind.TypeQuery) as TypeQueryNode;
         typeQueryNode.exprName = exprName;
@@ -455,21 +473,21 @@ namespace ts {
             : node;
     }
 
-    export function createIndexSignatureDeclaration(parameters: ParameterDeclaration[], type: TypeNode, decorators: Decorator[] | undefined, modifiers: Modifier[] | undefined): IndexSignatureDeclaration {
+    export function createIndexSignatureDeclaration(decorators: Decorator[] | undefined, modifiers: Modifier[] | undefined, parameters: ParameterDeclaration[], type: TypeNode): IndexSignatureDeclaration {
         const indexSignature = createSynthesizedNode(SyntaxKind.IndexSignature) as IndexSignatureDeclaration;
-        indexSignature.parameters = asNodeArray(parameters);
-        indexSignature.type = type;
         indexSignature.decorators = asNodeArray(decorators);
         indexSignature.modifiers = asNodeArray(modifiers);
+        indexSignature.parameters = createNodeArray(parameters);
+        indexSignature.type = type;
         return indexSignature;
     }
 
-    export function updateIndexSignatureDeclaration(node: IndexSignatureDeclaration, parameters: ParameterDeclaration[], type: TypeNode, decorators: Decorator[] | undefined, modifiers: Modifier[] | undefined) {
+    export function updateIndexSignatureDeclaration(node: IndexSignatureDeclaration, decorators: Decorator[] | undefined, modifiers: Modifier[] | undefined, parameters: ParameterDeclaration[], type: TypeNode) {
         return node.parameters !== parameters
             || node.type !== type
             || node.decorators !== decorators
             || node.modifiers !== modifiers
-            ? updateNode(createIndexSignatureDeclaration(parameters, type, decorators, modifiers), node)
+            ? updateNode(createIndexSignatureDeclaration(decorators, modifiers, parameters, type), node)
             : node;
     }
 
@@ -542,7 +560,7 @@ namespace ts {
         node.name = asName(name);
         node.questionToken = questionToken;
         node.typeParameters = asNodeArray(typeParameters);
-        node.parameters = asNodeArray(parameters);
+        node.parameters = createNodeArray(parameters);
         node.type = type;
         node.body = body;
         return node;
@@ -2052,7 +2070,8 @@ namespace ts {
     function asName(name: string | BindingName): BindingName;
     function asName(name: string | PropertyName): PropertyName;
     function asName(name: string | EntityName): EntityName;
-    function asName(name: string | Identifier | BindingName | PropertyName | QualifiedName) {
+    function asName(name: string | Identifier | ThisTypeNode): Identifier | ThisTypeNode;
+    function asName(name: string | Identifier | BindingName | PropertyName | QualifiedName | ThisTypeNode) {
         return typeof name === "string" ? createIdentifier(name) : name;
     }
 
@@ -2060,7 +2079,7 @@ namespace ts {
         return typeof value === "string" || typeof value === "number" ? createLiteral(value) : value;
     }
 
-    export function asNodeArray<T extends Node>(array: T[] | undefined): NodeArray<T> | undefined {
+    function asNodeArray<T extends Node>(array: T[] | undefined): NodeArray<T> | undefined {
         return array ? createNodeArray(array) : undefined;
     }
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 45a4de01c9..038f8bf316 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -1042,7 +1042,7 @@ namespace ts {
         kind: SyntaxKind.TrueKeyword | SyntaxKind.FalseKeyword;
     }
 
-    export interface ThisExpression extends PrimaryExpression, TypeNode {
+    export interface ThisExpression extends PrimaryExpression, KeywordTypeNode {
         kind: SyntaxKind.ThisKeyword;
     }
 
@@ -3248,12 +3248,6 @@ namespace ts {
         declaration?: SignatureDeclaration;
     }
 
-    export interface SignatureParts {
-        typeParameters: TypeParameterDeclaration[] | undefined;
-        parameters: ParameterDeclaration[];
-        type: TypeNode;
-    }
-
     /* @internal */
     export interface TypeMapper {
         (t: TypeParameter): Type;
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index f4f288d0cb..33cb0d8f48 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -3735,7 +3735,7 @@ namespace ts {
      * of a TypeNode.
      */
     export function isTypeNode(node: Node): node is TypeNode {
-        return node && isTypeNodeKind(node.kind);
+        return isTypeNodeKind(node.kind);
     }
 
     // Binding patterns
diff --git a/src/compiler/visitor.ts b/src/compiler/visitor.ts
index b8eb0210d0..c110ea4227 100644
--- a/src/compiler/visitor.ts
+++ b/src/compiler/visitor.ts
@@ -3,26 +3,6 @@
 /// <reference path="utilities.ts" />
 
 namespace ts {
-    export const nullTransformationContext: TransformationContext = {
-        enableEmitNotification: noop,
-        enableSubstitution: noop,
-        endLexicalEnvironment: () => undefined,
-        getCompilerOptions: notImplemented,
-        getEmitHost: notImplemented,
-        getEmitResolver: notImplemented,
-        hoistFunctionDeclaration: noop,
-        hoistVariableDeclaration: noop,
-        isEmitNotificationEnabled: notImplemented,
-        isSubstitutionEnabled: notImplemented,
-        onEmitNode: noop,
-        onSubstituteNode: notImplemented,
-        readEmitHelpers: notImplemented,
-        requestEmitHelper: noop,
-        resumeLexicalEnvironment: noop,
-        startLexicalEnvironment: noop,
-        suspendLexicalEnvironment: noop
-    };
-
     /**
      * Visits a Node using the supplied visitor, possibly returning a new Node in its place.
      *
@@ -234,7 +214,7 @@ namespace ts {
         const kind = node.kind;
 
         // No need to visit nodes with no children.
-        if ((kind > SyntaxKind.FirstToken && kind <= SyntaxKind.LastToken)) {
+        if ((kind > SyntaxKind.FirstToken && kind <= SyntaxKind.LastToken) || kind === SyntaxKind.ThisType) {
             return node;
         }
 
@@ -293,10 +273,10 @@ namespace ts {
 
             case SyntaxKind.IndexSignature:
                 return updateIndexSignatureDeclaration(<IndexSignatureDeclaration>node,
-                    visitParameterList((<IndexSignatureDeclaration>node).parameters, visitor, context, nodesVisitor),
-                    visitNode((<IndexSignatureDeclaration>node).type, visitor, isTypeNode),
                     nodesVisitor((<IndexSignatureDeclaration>node).decorators, visitor, isDecorator),
-                    nodesVisitor((<IndexSignatureDeclaration>node).modifiers, visitor, isModifier));
+                    nodesVisitor((<IndexSignatureDeclaration>node).modifiers, visitor, isModifier),
+                    visitParameterList((<IndexSignatureDeclaration>node).parameters, visitor, context, nodesVisitor),
+                    visitNode((<IndexSignatureDeclaration>node).type, visitor, isTypeNode));
 
             case SyntaxKind.Parameter:
                 return updateParameter(<ParameterDeclaration>node,
@@ -314,13 +294,16 @@ namespace ts {
 
             // Types
 
-            case SyntaxKind.TypePredicate:
-                throw new Error("reached unsupported type in visitor.");
             case SyntaxKind.TypeReference:
                 return updateTypeReferenceNode(<TypeReferenceNode>node,
                     visitNode((<TypeReferenceNode>node).typeName, visitor, isEntityName),
                     nodesVisitor((<TypeReferenceNode>node).typeArguments, visitor, isTypeNode));
 
+            case SyntaxKind.TypePredicate:
+                return updateTypePredicateNode(<TypePredicateNode>node,
+                    visitNode((<TypePredicateNode>node).parameterName, visitor),
+                    visitNode((<TypePredicateNode>node).type, visitor, isTypeNode));
+
             case SyntaxKind.TypeQuery:
                 return updateTypeQueryNode((<TypeQueryNode>node), visitNode((<TypeQueryNode>node).exprName, visitor, isEntityName));
 
@@ -339,9 +322,8 @@ namespace ts {
                     nodesVisitor((<UnionOrIntersectionTypeNode>node).types, visitor, isTypeNode));
 
             case SyntaxKind.ParenthesizedType:
-                throw new Error("reached unsupported type in visitor.");
-            case SyntaxKind.ThisType:
-                throw new Error("reached unsupported type in visitor.");
+                Debug.fail("not implemented.");
+
             case SyntaxKind.TypeOperator:
                 return updateTypeOperatorNode(<TypeOperatorNode>node, visitNode((<TypeOperatorNode>node).type, visitor, isTypeNode));
             case SyntaxKind.IndexedAccessType:
@@ -376,13 +358,6 @@ namespace ts {
                     visitNode((<PropertySignature>node).type, visitor, isTypeNode),
                     visitNode((<PropertySignature>node).initializer, visitor, isExpression));
 
-            case SyntaxKind.IndexSignature:
-                return updateIndexSignatureDeclaration(<IndexSignatureDeclaration>node,
-                    visitParameterList((<IndexSignatureDeclaration>node).parameters, visitor, context, nodesVisitor),
-                    visitNode((<IndexSignatureDeclaration>node).type, visitor, isTypeNode),
-                    nodesVisitor((<IndexSignatureDeclaration>node).decorators, visitor, isDecorator),
-                    nodesVisitor((<IndexSignatureDeclaration>node).modifiers, visitor, isModifier));
-
             case SyntaxKind.PropertyDeclaration:
                 return updateProperty(<PropertyDeclaration>node,
                     nodesVisitor((<PropertyDeclaration>node).decorators, visitor, isDecorator),
diff --git a/src/services/codefixes/fixAddMissingMember.ts b/src/services/codefixes/fixAddMissingMember.ts
index 4ef9fce067..bfb931e866 100644
--- a/src/services/codefixes/fixAddMissingMember.ts
+++ b/src/services/codefixes/fixAddMissingMember.ts
@@ -65,10 +65,10 @@ namespace ts.codefix {
             stringTypeNode,
             /*initializer*/ undefined);
         const indexSignature = createIndexSignatureDeclaration(
-            [indexingParameter],
-            typeNode,
             /*decorators*/undefined,
-            /*modifiers*/ undefined);
+            /*modifiers*/ undefined,
+            [indexingParameter],
+            typeNode);
 
         const indexSignatureChangeTracker = textChanges.ChangeTracker.fromCodeFixContext(context);
         indexSignatureChangeTracker.insertNodeAfter(sourceFile, openBrace, indexSignature, { suffix: context.newLineCharacter });
diff --git a/src/services/codefixes/helpers.ts b/src/services/codefixes/helpers.ts
index 49f95243c9..a7809cdd21 100644
--- a/src/services/codefixes/helpers.ts
+++ b/src/services/codefixes/helpers.ts
@@ -230,12 +230,4 @@ namespace ts.codefix {
         }
         return undefined;
     }
-
-    function stripComments(node: Node): Node {
-        if (node === undefined) {
-            return node;
-        }
-        const strippedChildren = visitEachChild(node, stripComments, nullTransformationContext);
-        return strippedChildren === node ? getSynthesizedClone(strippedChildren) : strippedChildren;
-    }
 }
\ No newline at end of file
diff --git a/src/services/textChanges.ts b/src/services/textChanges.ts
index f5b0ec678d..73d5fc61bc 100644
--- a/src/services/textChanges.ts
+++ b/src/services/textChanges.ts
@@ -528,6 +528,26 @@ namespace ts.textChanges {
         return skipTrivia(s, 0) === s.length;
     }
 
+    const nullTransformationContext: TransformationContext = {
+        enableEmitNotification: noop,
+        enableSubstitution: noop,
+        endLexicalEnvironment: () => undefined,
+        getCompilerOptions: notImplemented,
+        getEmitHost: notImplemented,
+        getEmitResolver: notImplemented,
+        hoistFunctionDeclaration: noop,
+        hoistVariableDeclaration: noop,
+        isEmitNotificationEnabled: notImplemented,
+        isSubstitutionEnabled: notImplemented,
+        onEmitNode: noop,
+        onSubstituteNode: notImplemented,
+        readEmitHelpers: notImplemented,
+        requestEmitHelper: noop,
+        resumeLexicalEnvironment: noop,
+        startLexicalEnvironment: noop,
+        suspendLexicalEnvironment: noop
+    };
+
     function assignPositionsToNode(node: Node): Node {
         const visited = visitEachChild(node, assignPositionsToNode, nullTransformationContext, assignPositionsToNodeArray, assignPositionsToNode);
         // create proxy node for non synthesized nodes
diff --git a/tests/cases/fourslash/codeFixClassImplementInterfaceMethodTypePredicate.ts b/tests/cases/fourslash/codeFixClassImplementInterfaceMethodTypePredicate.ts
new file mode 100644
index 0000000000..2eb6c2fabc
--- /dev/null
+++ b/tests/cases/fourslash/codeFixClassImplementInterfaceMethodTypePredicate.ts
@@ -0,0 +1,16 @@
+/// <reference path='fourslash.ts' />
+
+//// interface I {
+////     f(i: any): i is I;
+////     f(): this is I;
+//// }
+//// 
+//// class C implements I {[| |]}
+
+verify.rangeAfterCodeFix(`
+f(i: any): i is I;
+f(): this is I;
+f(i?: any) {
+    throw new Error("Method not implemented.");
+}
+`);