diff --git a/src/compiler/comments.ts b/src/compiler/comments.ts
index f9f8e74d4ca..116a8e849a3 100644
--- a/src/compiler/comments.ts
+++ b/src/compiler/comments.ts
@@ -5,7 +5,7 @@ namespace ts {
     export interface CommentWriter {
         reset(): void;
         setSourceFile(sourceFile: SourceFile): void;
-        emitNodeWithComments(node: Node, emitCallback: (node: Node) => void): void;
+        emitNodeWithComments(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void): void;
         emitBodyWithDetachedComments(node: Node, detachedRange: TextRange, emitCallback: (node: Node) => void): void;
         emitTrailingCommentsOfPosition(pos: number): void;
     }
@@ -34,9 +34,9 @@ namespace ts {
             emitTrailingCommentsOfPosition,
         };
 
-        function emitNodeWithComments(node: Node, emitCallback: (node: Node) => void) {
+        function emitNodeWithComments(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void) {
             if (disabled) {
-                emitCallback(node);
+                emitCallback(emitContext, node);
                 return;
             }
 
@@ -46,10 +46,12 @@ namespace ts {
                 if ((pos < 0 && end < 0) || (pos === end)) {
                     // Both pos and end are synthesized, so just emit the node without comments.
                     if (emitFlags & EmitFlags.NoNestedComments) {
-                        disableCommentsAndEmit(node, emitCallback);
+                        disabled = true;
+                        emitCallback(emitContext, node);
+                        disabled = false;
                     }
                     else {
-                        emitCallback(node);
+                        emitCallback(emitContext, node);
                     }
                 }
                 else {
@@ -91,10 +93,12 @@ namespace ts {
                     }
 
                     if (emitFlags & EmitFlags.NoNestedComments) {
-                        disableCommentsAndEmit(node, emitCallback);
+                        disabled = true;
+                        emitCallback(emitContext, node);
+                        disabled = false;
                     }
                     else {
-                        emitCallback(node);
+                        emitCallback(emitContext, node);
                     }
 
                     if (extendedDiagnostics) {
@@ -137,8 +141,10 @@ namespace ts {
                 performance.measure("commentTime", "preEmitBodyWithDetachedComments");
             }
 
-            if (emitFlags & EmitFlags.NoNestedComments) {
-                disableCommentsAndEmit(node, emitCallback);
+            if (emitFlags & EmitFlags.NoNestedComments && !disabled) {
+                disabled = true;
+                emitCallback(node);
+                disabled = false;
             }
             else {
                 emitCallback(node);
@@ -284,17 +290,6 @@ namespace ts {
             detachedCommentsInfo = undefined;
         }
 
-        function disableCommentsAndEmit(node: Node, emitCallback: (node: Node) => void): void {
-            if (disabled) {
-                emitCallback(node);
-            }
-            else {
-                disabled = true;
-                emitCallback(node);
-                disabled = false;
-            }
-        }
-
         function hasDetachedComments(pos: number) {
             return detachedCommentsInfo !== undefined && lastOrUndefined(detachedCommentsInfo).nodePos === pos;
         }
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 8457ea41d02..03f785dc7de 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -229,33 +229,27 @@ const _super = (function (geti, seti) {
         let isOwnFileEmit: boolean;
         let emitSkipped = false;
 
-        performance.mark("beforeTransform");
+        const sourceFiles = getSourceFilesToEmit(host, targetSourceFile);
 
         // Transform the source files
-        const transformed = transformFiles(
-            resolver,
-            host,
-            getSourceFilesToEmit(host, targetSourceFile),
-            transformers);
-
-        performance.measure("transformTime", "beforeTransform");
-
-        // Extract helpers from the result
+        performance.mark("beforeTransform");
         const {
+            transformed,
             emitNodeWithSubstitution,
             emitNodeWithNotification
-        } = transformed;
-
-        performance.mark("beforePrint");
+        } = transformFiles(resolver, host, sourceFiles, transformers);
+        performance.measure("transformTime", "beforeTransform");
 
         // Emit each output file
-        forEachTransformedEmitFile(host, transformed.getSourceFiles(), emitFile);
-
-        // Clean up after transformation
-        transformed.dispose();
-
+        performance.mark("beforePrint");
+        forEachTransformedEmitFile(host, transformed, emitFile);
         performance.measure("printTime", "beforePrint");
 
+        // Clean up emit nodes on parse tree
+        for (const sourceFile of sourceFiles) {
+            disposeEmitNodes(sourceFile);
+        }
+
         return {
             emitSkipped,
             diagnostics: emitterDiagnostics.getDiagnostics(),
@@ -346,111 +340,137 @@ const _super = (function (geti, seti) {
             currentFileIdentifiers = node.identifiers;
             sourceMap.setSourceFile(node);
             comments.setSourceFile(node);
-            emitNodeWithNotification(node, emitWithSubstitution);
+            pipelineEmitWithNotification(EmitContext.SourceFile, node);
         }
 
         /**
          * Emits a node.
          */
         function emit(node: Node) {
-            emitNodeWithNotification(node, emitWithComments);
-        }
-
-        /**
-         * Emits a node with comments.
-         *
-         * NOTE: Do not call this method directly. It is part of the emit pipeline
-         * and should only be called indirectly from emit.
-         */
-        function emitWithComments(node: Node) {
-            emitNodeWithComments(node, emitWithSourceMap);
-        }
-
-        /**
-         * Emits a node with source maps.
-         *
-         * NOTE: Do not call this method directly. It is part of the emit pipeline
-         * and should only be called indirectly from emitWithComments.
-         */
-        function emitWithSourceMap(node: Node) {
-            emitNodeWithSourceMap(node, emitWithSubstitution);
-        }
-
-        /**
-         * Emits a node with possible substitution.
-         *
-         * NOTE: Do not call this method directly. It is part of the emit pipeline
-         * and should only be called indirectly from emitWithSourceMap or
-         * emitIdentifierNameWithComments.
-         */
-        function emitWithSubstitution(node: Node) {
-            emitNodeWithSubstitution(node, /*isExpression*/ false, emitWorker);
+            pipelineEmitWithNotification(EmitContext.Unspecified, node);
         }
 
         /**
          * Emits an IdentifierName.
          */
         function emitIdentifierName(node: Identifier) {
-            if (node) {
-                emitNodeWithNotification(node, emitIdentifierNameWithComments);
-            }
-        }
-
-        /**
-         * Emits an IdentifierName with possible comments.
-         *
-         * NOTE: Do not call this method directly. It is part of the emit pipeline
-         * and should only be called indirectly from emitIdentifierName.
-         */
-        function emitIdentifierNameWithComments(node: Identifier) {
-            emitNodeWithComments(node, emitWithSubstitution);
+            pipelineEmitWithNotification(EmitContext.IdentifierName, node);
         }
 
         /**
          * Emits an expression node.
          */
         function emitExpression(node: Expression) {
-            emitNodeWithNotification(node, emitExpressionWithComments);
+            pipelineEmitWithNotification(EmitContext.Expression, node);
         }
 
         /**
-         * Emits an expression with comments.
+         * Emits a node with possible notification.
          *
-         * NOTE: Do not call this method directly. It is part of the emitExpression pipeline
-         * and should only be called indirectly from emitExpression.
+         * NOTE: Do not call this method directly. It is part of the emit pipeline
+         * and should only be called from printSourceFile, emit, emitExpression, or
+         * emitIdentifierName.
          */
-        function emitExpressionWithComments(node: Expression) {
-            emitNodeWithComments(node, emitExpressionWithSourceMap);
+        function pipelineEmitWithNotification(emitContext: EmitContext, node: Node) {
+            emitNodeWithNotification(emitContext, node, pipelineEmitWithComments);
         }
 
         /**
-         * Emits an expression with possible source maps.
+         * Emits a node with comments.
          *
-         * NOTE: Do not call this method directly. It is part of the emitExpression pipeline
-         * and should only be called indirectly from emitExpressionWithComments.
+         * NOTE: Do not call this method directly. It is part of the emit pipeline
+         * and should only be called indirectly from pipelineEmitWithNotification.
          */
-        function emitExpressionWithSourceMap(node: Expression) {
-            emitNodeWithSourceMap(node, emitExpressionWithSubstitution);
+        function pipelineEmitWithComments(emitContext: EmitContext, node: Node) {
+            // Do not emit comments for SourceFile
+            if (emitContext === EmitContext.SourceFile) {
+                pipelineEmitWithSourceMap(emitContext, node);
+                return;
+            }
+
+            emitNodeWithComments(emitContext, node, pipelineEmitWithSourceMap);
         }
 
         /**
-         * Emits an expression with possible substitution.
+         * Emits a node with source maps.
          *
-         * NOTE: Do not call this method directly. It is part of the emitExpression pipeline
-         * and should only be called indirectly from emitExpressionWithSourceMap or
-         * from emitWorker.
+         * NOTE: Do not call this method directly. It is part of the emit pipeline
+         * and should only be called indirectly from pipelineEmitWithComments.
          */
-        function emitExpressionWithSubstitution(node: Expression) {
-            emitNodeWithSubstitution(node, /*isExpression*/ true, emitExpressionWorker);
+        function pipelineEmitWithSourceMap(emitContext: EmitContext, node: Node) {
+            // Do not emit source mappings for SourceFile or IdentifierName
+            if (emitContext === EmitContext.SourceFile
+                || emitContext === EmitContext.IdentifierName) {
+                pipelineEmitWithSubstitution(emitContext, node);
+                return;
+            }
+
+            emitNodeWithSourceMap(emitContext, node, pipelineEmitWithSubstitution);
+        }
+
+        /**
+         * Emits a node with possible substitution.
+         *
+         * NOTE: Do not call this method directly. It is part of the emit pipeline
+         * and should only be called indirectly from pipelineEmitWithSourceMap or
+         * pipelineEmitInUnspecifiedContext (when pickign a more specific context).
+         */
+        function pipelineEmitWithSubstitution(emitContext: EmitContext, node: Node) {
+            emitNodeWithSubstitution(emitContext, node, pipelineEmitForContext);
         }
 
         /**
          * Emits a node.
          *
          * NOTE: Do not call this method directly. It is part of the emit pipeline
-         * and should only be called indirectly from emitNodeWithSubstitution.
+         * and should only be called indirectly from pipelineEmitWithSubstitution.
          */
-        function emitWorker(node: Node): void {
+        function pipelineEmitForContext(emitContext: EmitContext, node: Node): void {
+            switch (emitContext) {
+                case EmitContext.SourceFile: return pipelineEmitInSourceFileContext(node);
+                case EmitContext.IdentifierName: return pipelineEmitInIdentifierNameContext(node);
+                case EmitContext.Unspecified: return pipelineEmitInUnspecifiedContext(node);
+                case EmitContext.Expression: return pipelineEmitInExpressionContext(node);
+            }
+        }
+
+        /**
+         * Emits a node in the SourceFile EmitContext.
+         *
+         * NOTE: Do not call this method directly. It is part of the emit pipeline
+         * and should only be called indirectly from pipelineEmitForContext.
+         */
+        function pipelineEmitInSourceFileContext(node: Node): void {
+            const kind = node.kind;
+            switch (kind) {
+                // Top-level nodes
+                case SyntaxKind.SourceFile:
+                    return emitSourceFile(<SourceFile>node);
+            }
+        }
+
+        /**
+         * Emits a node in the IdentifierName EmitContext.
+         *
+         * NOTE: Do not call this method directly. It is part of the emit pipeline
+         * and should only be called indirectly from pipelineEmitForContext.
+         */
+        function pipelineEmitInIdentifierNameContext(node: Node): void {
+            const kind = node.kind;
+            switch (kind) {
+                // Identifiers
+                case SyntaxKind.Identifier:
+                    return emitIdentifier(<Identifier>node);
+            }
+        }
+
+        /**
+         * Emits a node in the Unspecified EmitContext.
+         *
+         * NOTE: Do not call this method directly. It is part of the emit pipeline
+         * and should only be called indirectly from pipelineEmitForContext.
+         */
+        function pipelineEmitInUnspecifiedContext(node: Node): void {
             const kind = node.kind;
             switch (kind) {
                 // Pseudo-literals
@@ -486,7 +506,8 @@ const _super = (function (geti, seti) {
                 case SyntaxKind.StringKeyword:
                 case SyntaxKind.SymbolKeyword:
                 case SyntaxKind.GlobalKeyword:
-                    return emitTokenNode(node);
+                    writeTokenText(kind);
+                    return;
 
                 // Parse tree nodes
 
@@ -691,27 +712,24 @@ const _super = (function (geti, seti) {
                 case SyntaxKind.EnumMember:
                     return emitEnumMember(<EnumMember>node);
 
-                // Top-level nodes
-                case SyntaxKind.SourceFile:
-                    return emitSourceFile(<SourceFile>node);
-
                 // JSDoc nodes (ignored)
-
                 // Transformation nodes (ignored)
             }
 
+            // If the node is an expression, try to emit it as an expression with
+            // substitution.
             if (isExpression(node)) {
-                return emitExpressionWithSubstitution(node);
+                return pipelineEmitWithSubstitution(EmitContext.Expression, node);
             }
         }
 
         /**
-         * Emits an expression.
+         * Emits a node in the Expression EmitContext.
          *
-         * NOTE: Do not call this method directly. It is part of the emitExpression pipeline
-         * and should only be called indirectly from emitExpressionWithNotification.
+         * NOTE: Do not call this method directly. It is part of the emit pipeline
+         * and should only be called indirectly from pipelineEmitForContext.
          */
-        function emitExpressionWorker(node: Node) {
+        function pipelineEmitInExpressionContext(node: Node): void {
             const kind = node.kind;
             switch (kind) {
                 // Literals
@@ -733,7 +751,8 @@ const _super = (function (geti, seti) {
                 case SyntaxKind.SuperKeyword:
                 case SyntaxKind.TrueKeyword:
                 case SyntaxKind.ThisKeyword:
-                    return emitTokenNode(node);
+                    writeTokenText(kind);
+                    return;
 
                 // Expressions
                 case SyntaxKind.ArrayLiteralExpression:
@@ -2444,15 +2463,7 @@ const _super = (function (geti, seti) {
         function writeTokenText(token: SyntaxKind, pos?: number) {
             const tokenString = tokenToString(token);
             write(tokenString);
-            return positionIsSynthesized(pos) ? -1 : pos + tokenString.length;
-        }
-
-        function emitTokenNode(node: Node) {
-            emitNodeWithSourceMap(node, emitTokenNodeWorker);
-        }
-
-        function emitTokenNodeWorker(node: Node) {
-            writeTokenText(node.kind);
+            return pos < 0 ? pos : pos + tokenString.length;
         }
 
         function increaseIndentIf(value: boolean, valueToWriteWhenNotIndenting?: string) {
diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index c0565f6e91d..b6fc2093288 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -2665,6 +2665,139 @@ namespace ts {
         return destRanges;
     }
 
+    /**
+     * Clears any EmitNode entries from parse-tree nodes.
+     * @param sourceFile A source file.
+     */
+    export function disposeEmitNodes(sourceFile: SourceFile) {
+        // During transformation we may need to annotate a parse tree node with transient
+        // transformation properties. As parse tree nodes live longer than transformation
+        // nodes, we need to make sure we reclaim any memory allocated for custom ranges
+        // from these nodes to ensure we do not hold onto entire subtrees just for position
+        // information. We also need to reset these nodes to a pre-transformation state
+        // for incremental parsing scenarios so that we do not impact later emit.
+        sourceFile = getSourceFileOfNode(getParseTreeNode(sourceFile));
+        const emitNode = sourceFile && sourceFile.emitNode;
+        const annotatedNodes = emitNode && emitNode.annotatedNodes;
+        if (annotatedNodes) {
+            for (const node of annotatedNodes) {
+                node.emitNode = undefined;
+            }
+        }
+    }
+
+    /**
+     * Associates a node with the current transformation, initializing
+     * various transient transformation properties.
+     *
+     * @param node The node.
+     */
+    function getOrCreateEmitNode(node: Node) {
+        if (!node.emitNode) {
+            if (isParseTreeNode(node)) {
+                // To avoid holding onto transformation artifacts, we keep track of any
+                // parse tree node we are annotating. This allows us to clean them up after
+                // all transformations have completed.
+                if (node.kind === SyntaxKind.SourceFile) {
+                    return node.emitNode = { annotatedNodes: [node] };
+                }
+
+                const sourceFile = getSourceFileOfNode(node);
+                getOrCreateEmitNode(sourceFile).annotatedNodes.push(node);
+            }
+
+            node.emitNode = {};
+        }
+
+        return node.emitNode;
+    }
+
+    /**
+     * Gets flags that control emit behavior of a node.
+     *
+     * @param node The node.
+     */
+    export function getEmitFlags(node: Node) {
+        const emitNode = node.emitNode;
+        return emitNode && emitNode.flags;
+    }
+
+    /**
+     * Sets flags that control emit behavior of a node.
+     *
+     * @param node The node.
+     * @param emitFlags The NodeEmitFlags for the node.
+     */
+    export function setEmitFlags<T extends Node>(node: T, emitFlags: EmitFlags) {
+        getOrCreateEmitNode(node).flags = emitFlags;
+        return node;
+    }
+
+    /**
+     * Sets a custom text range to use when emitting source maps.
+     *
+     * @param node The node.
+     * @param range The text range.
+     */
+    export function setSourceMapRange<T extends Node>(node: T, range: TextRange) {
+        getOrCreateEmitNode(node).sourceMapRange = range;
+        return node;
+    }
+
+    /**
+     * Sets the TextRange to use for source maps for a token of a node.
+     *
+     * @param node The node.
+     * @param token The token.
+     * @param range The text range.
+     */
+    export function setTokenSourceMapRange<T extends Node>(node: T, token: SyntaxKind, range: TextRange) {
+        const emitNode = getOrCreateEmitNode(node);
+        const tokenSourceMapRanges = emitNode.tokenSourceMapRanges || (emitNode.tokenSourceMapRanges = createMap<TextRange>());
+        tokenSourceMapRanges[token] = range;
+        return node;
+    }
+
+    /**
+     * Sets a custom text range to use when emitting comments.
+     */
+    export function setCommentRange<T extends Node>(node: T, range: TextRange) {
+        getOrCreateEmitNode(node).commentRange = range;
+        return node;
+    }
+
+    /**
+     * Gets a custom text range to use when emitting comments.
+     *
+     * @param node The node.
+     */
+    export function getCommentRange(node: Node) {
+        const emitNode = node.emitNode;
+        return (emitNode && emitNode.commentRange) || node;
+    }
+
+    /**
+     * Gets a custom text range to use when emitting source maps.
+     *
+     * @param node The node.
+     */
+    export function getSourceMapRange(node: Node) {
+        const emitNode = node.emitNode;
+        return (emitNode && emitNode.sourceMapRange) || node;
+    }
+
+    /**
+     * Gets the TextRange to use for source maps for a token of a node.
+     *
+     * @param node The node.
+     * @param token The token.
+     */
+    export function getTokenSourceMapRange(node: Node, token: SyntaxKind) {
+        const emitNode = node.emitNode;
+        const tokenSourceMapRanges = emitNode && emitNode.tokenSourceMapRanges;
+        return tokenSourceMapRanges && tokenSourceMapRanges[token];
+    }
+
     export function setTextRange<T extends TextRange>(node: T, location: TextRange): T {
         if (location) {
             node.pos = location.pos;
@@ -2706,7 +2839,7 @@ namespace ts {
         return undefined;
     }
 
-   /**
+    /**
      * Get the name of a target module from an import/export declaration as should be written in the emitted output.
      * The emitted output name can be different from the input if:
      *  1. The module has a /// <amd-module name="<new name>" />
diff --git a/src/compiler/sourcemap.ts b/src/compiler/sourcemap.ts
index 3517c54b407..d6e6501c598 100644
--- a/src/compiler/sourcemap.ts
+++ b/src/compiler/sourcemap.ts
@@ -38,10 +38,11 @@ namespace ts {
         /**
          * Emits a node with possible leading and trailing source maps.
          *
+         * @param emitContext The current emit context
          * @param node The node to emit.
          * @param emitCallback The callback used to emit the node.
          */
-        emitNodeWithSourceMap(node: Node, emitCallback: (node: Node) => void): void;
+        emitNodeWithSourceMap(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void): void;
 
         /**
          * Emits a token of a node node with possible leading and trailing source maps.
@@ -313,9 +314,9 @@ namespace ts {
          * @param node The node to emit.
          * @param emitCallback The callback used to emit the node.
          */
-        function emitNodeWithSourceMap(node: Node, emitCallback: (node: Node) => void) {
+        function emitNodeWithSourceMap(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void) {
             if (disabled) {
-                return emitCallback(node);
+                return emitCallback(emitContext, node);
             }
 
             if (node) {
@@ -331,11 +332,11 @@ namespace ts {
 
                 if (emitFlags & EmitFlags.NoNestedSourceMaps) {
                     disabled = true;
-                    emitCallback(node);
+                    emitCallback(emitContext, node);
                     disabled = false;
                 }
                 else {
-                    emitCallback(node);
+                    emitCallback(emitContext, node);
                 }
 
                 if (node.kind !== SyntaxKind.NotEmittedStatement
diff --git a/src/compiler/transformer.ts b/src/compiler/transformer.ts
index 5695bea7ae9..92407af2bb9 100644
--- a/src/compiler/transformer.ts
+++ b/src/compiler/transformer.ts
@@ -28,29 +28,25 @@ namespace ts {
         /**
          * Gets the transformed source files.
          */
-        getSourceFiles(): SourceFile[];
+        transformed: SourceFile[];
 
         /**
          * Emits the substitute for a node, if one is available; otherwise, emits the node.
          *
+         * @param emitContext The current emit context.
          * @param node The node to substitute.
-         * @param isExpression A value indicating whether the node is in an expression context.
          * @param emitCallback A callback used to emit the node or its substitute.
          */
-        emitNodeWithSubstitution(node: Node, isExpression: boolean, emitCallback: (node: Node) => void): void;
+        emitNodeWithSubstitution(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void): void;
 
         /**
          * Emits a node with possible notification.
          *
+         * @param emitContext The current emit context.
          * @param node The node to emit.
          * @param emitCallback A callback used to emit the node.
          */
-        emitNodeWithNotification(node: Node, emitCallback: (node: Node) => void): void;
-
-        /**
-         * Reset transient transformation properties on parse tree nodes.
-         */
-        dispose(): void;
+        emitNodeWithNotification(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void): void;
     }
 
     export interface TransformationContext extends LexicalEnvironment {
@@ -82,7 +78,7 @@ namespace ts {
          * Hook used by transformers to substitute expressions just before they
          * are emitted by the pretty printer.
          */
-        onSubstituteNode?: (node: Node, isExpression: boolean) => Node;
+        onSubstituteNode?: (emitContext: EmitContext, node: Node) => Node;
 
         /**
          * Enables before/after emit notifications in the pretty printer for the provided
@@ -100,7 +96,7 @@ namespace ts {
          * Hook used to allow transformers to capture state before or after
          * the printer emits a node.
          */
-        onEmitNode?: (node: Node, emit: (node: Node) => void) => void;
+        onEmitNode?: (emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void) => void;
     }
 
     /* @internal */
@@ -129,139 +125,6 @@ namespace ts {
         return transformers;
     }
 
-    /**
-     * Clears any EmitNode entries from parse-tree nodes.
-     * @param sourceFile A source file.
-     */
-    export function disposeEmitNodes(sourceFile: SourceFile) {
-        // During transformation we may need to annotate a parse tree node with transient
-        // transformation properties. As parse tree nodes live longer than transformation
-        // nodes, we need to make sure we reclaim any memory allocated for custom ranges
-        // from these nodes to ensure we do not hold onto entire subtrees just for position
-        // information. We also need to reset these nodes to a pre-transformation state
-        // for incremental parsing scenarios so that we do not impact later emit.
-        sourceFile = getSourceFileOfNode(getParseTreeNode(sourceFile));
-        const emitNode = sourceFile && sourceFile.emitNode;
-        const annotatedNodes = emitNode && emitNode.annotatedNodes;
-        if (annotatedNodes) {
-            for (const node of annotatedNodes) {
-                node.emitNode = undefined;
-            }
-        }
-    }
-
-    /**
-     * Associates a node with the current transformation, initializing
-     * various transient transformation properties.
-     *
-     * @param node The node.
-     */
-    function getOrCreateEmitNode(node: Node) {
-        if (!node.emitNode) {
-            if (isParseTreeNode(node)) {
-                // To avoid holding onto transformation artifacts, we keep track of any
-                // parse tree node we are annotating. This allows us to clean them up after
-                // all transformations have completed.
-                if (node.kind === SyntaxKind.SourceFile) {
-                    return node.emitNode = { annotatedNodes: [node] };
-                }
-
-                const sourceFile = getSourceFileOfNode(node);
-                getOrCreateEmitNode(sourceFile).annotatedNodes.push(node);
-            }
-
-            node.emitNode = {};
-        }
-
-        return node.emitNode;
-    }
-
-    /**
-     * Gets flags that control emit behavior of a node.
-     *
-     * @param node The node.
-     */
-    export function getEmitFlags(node: Node) {
-        const emitNode = node.emitNode;
-        return emitNode && emitNode.flags;
-    }
-
-    /**
-     * Sets flags that control emit behavior of a node.
-     *
-     * @param node The node.
-     * @param emitFlags The NodeEmitFlags for the node.
-     */
-    export function setEmitFlags<T extends Node>(node: T, emitFlags: EmitFlags) {
-        getOrCreateEmitNode(node).flags = emitFlags;
-        return node;
-    }
-
-    /**
-     * Sets a custom text range to use when emitting source maps.
-     *
-     * @param node The node.
-     * @param range The text range.
-     */
-    export function setSourceMapRange<T extends Node>(node: T, range: TextRange) {
-        getOrCreateEmitNode(node).sourceMapRange = range;
-        return node;
-    }
-
-    /**
-     * Sets the TextRange to use for source maps for a token of a node.
-     *
-     * @param node The node.
-     * @param token The token.
-     * @param range The text range.
-     */
-    export function setTokenSourceMapRange<T extends Node>(node: T, token: SyntaxKind, range: TextRange) {
-        const emitNode = getOrCreateEmitNode(node);
-        const tokenSourceMapRanges = emitNode.tokenSourceMapRanges || (emitNode.tokenSourceMapRanges = createMap<TextRange>());
-        tokenSourceMapRanges[token] = range;
-        return node;
-    }
-
-    /**
-     * Sets a custom text range to use when emitting comments.
-     */
-    export function setCommentRange<T extends Node>(node: T, range: TextRange) {
-        getOrCreateEmitNode(node).commentRange = range;
-        return node;
-    }
-
-    /**
-     * Gets a custom text range to use when emitting comments.
-     *
-     * @param node The node.
-     */
-    export function getCommentRange(node: Node) {
-        const emitNode = node.emitNode;
-        return (emitNode && emitNode.commentRange) || node;
-    }
-
-    /**
-     * Gets a custom text range to use when emitting source maps.
-     *
-     * @param node The node.
-     */
-    export function getSourceMapRange(node: Node) {
-        const emitNode = node.emitNode;
-        return (emitNode && emitNode.sourceMapRange) || node;
-    }
-
-    /**
-     * Gets the TextRange to use for source maps for a token of a node.
-     *
-     * @param node The node.
-     * @param token The token.
-     */
-    export function getTokenSourceMapRange(node: Node, token: SyntaxKind) {
-        const emitNode = node.emitNode;
-        const tokenSourceMapRanges = emitNode && emitNode.tokenSourceMapRanges;
-        return tokenSourceMapRanges && tokenSourceMapRanges[token];
-    }
-
     /**
      * Transforms an array of SourceFiles by passing them through each transformer.
      *
@@ -290,10 +153,10 @@ namespace ts {
             hoistFunctionDeclaration,
             startLexicalEnvironment,
             endLexicalEnvironment,
-            onSubstituteNode: (node, isExpression) => node,
+            onSubstituteNode: (emitContext, node) => node,
             enableSubstitution,
             isSubstitutionEnabled,
-            onEmitNode: (node, emitCallback) => emitCallback(node),
+            onEmitNode: (node, emitContext, emitCallback) => emitCallback(node, emitContext),
             enableEmitNotification,
             isEmitNotificationEnabled
         };
@@ -308,20 +171,9 @@ namespace ts {
         lexicalEnvironmentDisabled = true;
 
         return {
-            getSourceFiles: () => transformed,
+            transformed,
             emitNodeWithSubstitution,
-            emitNodeWithNotification,
-            dispose() {
-                // During transformation we may need to annotate a parse tree node with transient
-                // transformation properties. As parse tree nodes live longer than transformation
-                // nodes, we need to make sure we reclaim any memory allocated for custom ranges
-                // from these nodes to ensure we do not hold onto entire subtrees just for position
-                // information. We also need to reset these nodes to a pre-transformation state
-                // for incremental parsing scenarios so that we do not impact later emit.
-                for (const sourceFile of sourceFiles) {
-                    disposeEmitNodes(sourceFile);
-                }
-            }
+            emitNodeWithNotification
         };
 
         /**
@@ -355,21 +207,21 @@ namespace ts {
         /**
          * Emits a node with possible substitution.
          *
+         * @param emitContext The current emit context.
          * @param node The node to emit.
-         * @param isExpression Whether the node represents an expression.
          * @param emitCallback The callback used to emit the node or its substitute.
          */
-        function emitNodeWithSubstitution(node: Node, isExpression: boolean, emitCallback: (node: Node) => void) {
+        function emitNodeWithSubstitution(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void) {
             if (node) {
                 if (isSubstitutionEnabled(node)) {
-                    const substitute = context.onSubstituteNode(node, isExpression);
+                    const substitute = context.onSubstituteNode(emitContext, node);
                     if (substitute && substitute !== node) {
-                        emitCallback(substitute);
+                        emitCallback(emitContext, substitute);
                         return;
                     }
                 }
 
-                emitCallback(node);
+                emitCallback(emitContext, node);
             }
         }
 
@@ -391,14 +243,18 @@ namespace ts {
 
         /**
          * Emits a node with possible emit notification.
+         *
+         * @param emitContext The current emit context.
+         * @param node The node to emit.
+         * @param emitCallback The callback used to emit the node.
          */
-        function emitNodeWithNotification(node: Node, emitCallback: (node: Node) => void) {
+        function emitNodeWithNotification(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void) {
             if (node) {
                 if (isEmitNotificationEnabled(node)) {
-                    context.onEmitNode(node, emitCallback);
+                    context.onEmitNode(emitContext, node, emitCallback);
                 }
                 else {
-                    emitCallback(node);
+                    emitCallback(emitContext, node);
                 }
             }
         }
diff --git a/src/compiler/transformers/es6.ts b/src/compiler/transformers/es6.ts
index eda0d03c704..589478f1f6f 100644
--- a/src/compiler/transformers/es6.ts
+++ b/src/compiler/transformers/es6.ts
@@ -2852,7 +2852,7 @@ namespace ts {
          *
          * @param node The node to be printed.
          */
-        function onEmitNode(node: Node, emit: (node: Node) => void) {
+        function onEmitNode(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void) {
             const savedUseCapturedThis = useCapturedThis;
 
             if (enabledSubstitutions & ES6SubstitutionFlags.CapturedThis && isFunctionLike(node)) {
@@ -2861,7 +2861,7 @@ namespace ts {
                 useCapturedThis = (getEmitFlags(node) & EmitFlags.CapturesThis) !== 0;
             }
 
-            previousOnEmitNode(node, emit);
+            previousOnEmitNode(emitContext, node, emitCallback);
 
             useCapturedThis = savedUseCapturedThis;
         }
@@ -2902,10 +2902,10 @@ namespace ts {
          * @param isExpression A value indicating whether the node is to be used in an expression
          *                     position.
          */
-        function onSubstituteNode(node: Node, isExpression: boolean) {
-            node = previousOnSubstituteNode(node, isExpression);
+        function onSubstituteNode(emitContext: EmitContext, node: Node) {
+            node = previousOnSubstituteNode(emitContext, node);
 
-            if (isExpression) {
+            if (emitContext === EmitContext.Expression) {
                 return substituteExpression(node);
             }
 
diff --git a/src/compiler/transformers/generators.ts b/src/compiler/transformers/generators.ts
index d6a30a81d61..58c18fdbc5d 100644
--- a/src/compiler/transformers/generators.ts
+++ b/src/compiler/transformers/generators.ts
@@ -1883,9 +1883,9 @@ namespace ts {
             return -1;
         }
 
-        function onSubstituteNode(node: Node, isExpression: boolean): Node {
-            node = previousOnSubstituteNode(node, isExpression);
-            if (isExpression) {
+        function onSubstituteNode(emitContext: EmitContext, node: Node): Node {
+            node = previousOnSubstituteNode(emitContext, node);
+            if (emitContext === EmitContext.Expression) {
                 return substituteExpression(<Expression>node);
             }
             return node;
diff --git a/src/compiler/transformers/module/module.ts b/src/compiler/transformers/module/module.ts
index 286ef967288..8bcf8f5fb25 100644
--- a/src/compiler/transformers/module/module.ts
+++ b/src/compiler/transformers/module/module.ts
@@ -822,14 +822,14 @@ namespace ts {
             return node.name ? getSynthesizedClone(node.name) : getGeneratedNameForNode(node);
         }
 
-        function onEmitNode(node: Node, emit: (node: Node) => void): void {
+        function onEmitNode(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void): void {
             if (node.kind === SyntaxKind.SourceFile) {
                 bindingNameExportSpecifiersMap = bindingNameExportSpecifiersForFileMap[getOriginalNodeId(node)];
-                previousOnEmitNode(node, emit);
+                previousOnEmitNode(emitContext, node, emitCallback);
                 bindingNameExportSpecifiersMap = undefined;
             }
             else {
-                previousOnEmitNode(node, emit);
+                previousOnEmitNode(emitContext, node, emitCallback);
             }
         }
 
@@ -840,9 +840,9 @@ namespace ts {
          * @param isExpression A value indicating whether the node is to be used in an expression
          *                     position.
          */
-        function onSubstituteNode(node: Node, isExpression: boolean) {
-            node = previousOnSubstituteNode(node, isExpression);
-            if (isExpression) {
+        function onSubstituteNode(emitContext: EmitContext, node: Node) {
+            node = previousOnSubstituteNode(emitContext, node);
+            if (emitContext === EmitContext.Expression) {
                 return substituteExpression(<Expression>node);
             }
             else if (isShorthandPropertyAssignment(node)) {
diff --git a/src/compiler/transformers/module/system.ts b/src/compiler/transformers/module/system.ts
index 2a14f341272..7e5b36d239c 100644
--- a/src/compiler/transformers/module/system.ts
+++ b/src/compiler/transformers/module/system.ts
@@ -986,14 +986,14 @@ namespace ts {
         // Substitutions
         //
 
-        function onEmitNode(node: Node, emit: (node: Node) => void): void {
+        function onEmitNode(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void): void {
             if (node.kind === SyntaxKind.SourceFile) {
                 exportFunctionForFile = exportFunctionForFileMap[getOriginalNodeId(node)];
-                previousOnEmitNode(node, emit);
+                previousOnEmitNode(emitContext, node, emitCallback);
                 exportFunctionForFile = undefined;
             }
             else {
-                previousOnEmitNode(node, emit);
+                previousOnEmitNode(emitContext, node, emitCallback);
             }
         }
 
@@ -1004,9 +1004,9 @@ namespace ts {
          * @param isExpression A value indicating whether the node is to be used in an expression
          *                     position.
          */
-        function onSubstituteNode(node: Node, isExpression: boolean) {
-            node = previousOnSubstituteNode(node, isExpression);
-            if (isExpression) {
+        function onSubstituteNode(emitContext: EmitContext, node: Node) {
+            node = previousOnSubstituteNode(emitContext, node);
+            if (emitContext === EmitContext.Expression) {
                 return substituteExpression(<Expression>node);
             }
 
diff --git a/src/compiler/transformers/ts.ts b/src/compiler/transformers/ts.ts
index e1892ff5bf4..225ab130d62 100644
--- a/src/compiler/transformers/ts.ts
+++ b/src/compiler/transformers/ts.ts
@@ -3231,7 +3231,7 @@ namespace ts {
          * @param node The node to emit.
          * @param emit A callback used to emit the node in the printer.
          */
-        function onEmitNode(node: Node, emit: (node: Node) => void): void {
+        function onEmitNode(emitContext: EmitContext, node: Node, emitCallback: (emitContext: EmitContext, node: Node) => void): void {
             const savedApplicableSubstitutions = applicableSubstitutions;
             const savedCurrentSuperContainer = currentSuperContainer;
             // If we need to support substitutions for `super` in an async method,
@@ -3248,7 +3248,7 @@ namespace ts {
                 applicableSubstitutions |= TypeScriptSubstitutionFlags.NonQualifiedEnumMembers;
             }
 
-            previousOnEmitNode(node, emit);
+            previousOnEmitNode(emitContext, node, emitCallback);
 
             applicableSubstitutions = savedApplicableSubstitutions;
             currentSuperContainer = savedCurrentSuperContainer;
@@ -3261,9 +3261,9 @@ namespace ts {
          * @param isExpression A value indicating whether the node is to be used in an expression
          *                     position.
          */
-        function onSubstituteNode(node: Node, isExpression: boolean) {
-            node = previousOnSubstituteNode(node, isExpression);
-            if (isExpression) {
+        function onSubstituteNode(emitContext: EmitContext, node: Node) {
+            node = previousOnSubstituteNode(emitContext, node);
+            if (emitContext === EmitContext.Expression) {
                 return substituteExpression(<Expression>node);
             }
             else if (isShorthandPropertyAssignment(node)) {
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index c18ebdd7200..74e7e741be8 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -3189,6 +3189,14 @@ namespace ts {
         CustomPrologue = 1 << 23,                // Treat the statement as if it were a prologue directive (NOTE: Prologue directives are *not* transformed).
     }
 
+    /* @internal */
+    export const enum EmitContext {
+        SourceFile,         // Emitting a SourceFile
+        Expression,         // Emitting an Expression
+        IdentifierName,     // Emitting an IdentifierName
+        Unspecified,        // Emitting an otherwise unspecified node
+    }
+
     /** Additional context provided to `visitEachChild` */
     /* @internal */
     export interface LexicalEnvironment {