From 329d3d5f13049daef4f2e10240a739ec2ae63696 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Sun, 2 Nov 2014 19:31:31 -0800
Subject: [PATCH] Speed up incremental parsing

---
 src/services/syntax/syntax.ts        |  8 ++---
 src/services/syntax/syntaxElement.ts | 48 +++++++++++++---------------
 2 files changed, 27 insertions(+), 29 deletions(-)

diff --git a/src/services/syntax/syntax.ts b/src/services/syntax/syntax.ts
index 2f0b5853bd8..f1081f49021 100644
--- a/src/services/syntax/syntax.ts
+++ b/src/services/syntax/syntax.ts
@@ -184,8 +184,8 @@ module TypeScript.Syntax {
         return <ISyntaxNode>current;
     }
 
-    export function findTokenOnLeft(element: ISyntaxElement, position: number): ISyntaxToken {
-        var positionedToken = findToken(element, position);
+    export function findTokenOnLeft(sourceUnit: SourceUnitSyntax, position: number): ISyntaxToken {
+        var positionedToken = findToken(sourceUnit, position);
         var _start = start(positionedToken);
 
         // Position better fall within this token.
@@ -206,8 +206,8 @@ module TypeScript.Syntax {
         return previousToken(positionedToken);
     }
 
-    export function findCompleteTokenOnLeft(element: ISyntaxElement, position: number): ISyntaxToken {
-        var positionedToken = findToken(element, position);
+    export function findCompleteTokenOnLeft(sourceUnit: SourceUnitSyntax, position: number): ISyntaxToken {
+        var positionedToken = findToken(sourceUnit, position);
 
         // Position better fall within this token.
         // Debug.assert(position >= positionedToken.fullStart());
diff --git a/src/services/syntax/syntaxElement.ts b/src/services/syntax/syntaxElement.ts
index d6d7b374e7d..11f46ba1b54 100644
--- a/src/services/syntax/syntaxElement.ts
+++ b/src/services/syntax/syntaxElement.ts
@@ -58,18 +58,26 @@ module TypeScript {
      * Note: findToken will always return a non-missing token with width greater than or equal to
      * 1 (except for EOF).  Empty tokens synthesized by the parser are never returned.
      */
-    export function findToken(element: ISyntaxElement, position: number): ISyntaxToken {
-        var endOfFileToken = tryGetEndOfFileAt(element, position);
-        if (endOfFileToken) {
-            return endOfFileToken;
-        }
-
-        if (position < 0 || position >= fullWidth(element)) {
+    export function findToken(sourceUnit: SourceUnitSyntax, position: number): ISyntaxToken {
+        if (position < 0) {
             throw Errors.argumentOutOfRange("position");
         }
 
-        var positionedToken = findTokenWorker(element, 0, position);
-        return positionedToken;
+        var token = findTokenWorker(sourceUnit, 0, position);
+        if (token) {
+            Debug.assert(token.fullWidth() > 0);
+            return token;
+        }
+
+        if (position === fullWidth(sourceUnit)) {
+            return sourceUnit.endOfFileToken;
+        }
+
+        if (position > fullWidth(sourceUnit)) {
+            throw Errors.argumentOutOfRange("position");
+        }
+
+        throw Errors.invalidOperation();
     }
 
     export function findSkippedTokenInPositionedToken(positionedToken: ISyntaxToken, position: number): ISyntaxToken {
@@ -115,37 +123,27 @@ module TypeScript {
     }
 
     function findTokenWorker(element: ISyntaxElement, elementPosition: number, position: number): ISyntaxToken {
-        // Debug.assert(position >= 0 && position < this.fullWidth());
         if (isToken(element)) {
-            Debug.assert(fullWidth(element) > 0);
             return <ISyntaxToken>element;
         }
 
-        if (isShared(element)) {
-            // This should never have been called on this element.  It has a 0 width, so the client 
-            // should have skipped over this.
-            throw Errors.invalidOperation();
-        }
-
         // Consider: we could use a binary search here to find the child more quickly.
         for (var i = 0, n = element.childCount(); i < n; i++) {
             var child = element.childAt(i);
 
             if (child) {
                 var childFullWidth = fullWidth(child);
-                if (childFullWidth > 0) {
-                    var elementEndPosition = elementPosition + childFullWidth;
+                var elementEndPosition = elementPosition + childFullWidth;
 
-                    if (position < elementEndPosition) {
-                        return findTokenWorker(child, elementPosition, position);
-                    }
-
-                    elementPosition = elementEndPosition;
+                if (position < elementEndPosition) {
+                    return findTokenWorker(child, elementPosition, position);
                 }
+
+                elementPosition = elementEndPosition;
             }
         }
 
-        throw Errors.invalidOperation();
+        return undefined;
     }
 
     function tryGetEndOfFileAt(element: ISyntaxElement, position: number): ISyntaxToken {