Make utility method names clearer.

src/compiler/types.ts

@@ -325,14 +325,12 @@ module ts {
 
         // Context flags computed by aggregating child flags upwards.
 
-        // If this node, or any of it's children (transitively) contain an error.  
+        // Used during incremental parsing to determine if this node or any of its children had an 
+        // error.  Computed only once and then cached.
         ThisNodeOrAnySubNodesHasError = 1 << 5,
 
-        // Used during incremental parsing to determine if we need to visit this node to see if
-        // any of its children had an error.  Once we compute that once, we can set this bit on the
-        // node to know that we never have to do it again.  From that point on, we can just check
-        // the node directly for 'ContainsError'.
-        HasComputedThisNodeOrAnySubNodesHasError = 1 << 6
+        // Used to know if we've computed data from children and cached it in this node.
+        HasAggregatedChildData = 1 << 6
     }
 
     export interface Node extends TextRange {

src/compiler/utilities.ts

@@ -62,31 +62,34 @@ module ts {
         return node.end - node.pos;
     }
 
-    export function hasFlag(val: number, flag: number): boolean {
+    function hasFlag(val: number, flag: number): boolean {
         return (val & flag) !== 0;
     }
 
     // Returns true if this node contains a parse error anywhere underneath it.
     export function containsParseError(node: Node): boolean {
-        if (!hasFlag(node.parserContextFlags, ParserContextFlags.HasComputedThisNodeOrAnySubNodesHasError)) {
+        aggregateChildData(node);
+        return hasFlag(node.parserContextFlags, ParserContextFlags.ThisNodeOrAnySubNodesHasError);
+    }
+
+    function aggregateChildData(node: Node): void {
+        if (!hasFlag(node.parserContextFlags, ParserContextFlags.HasAggregatedChildData)) {
             // A node is considered to contain a parse error if:
             //  a) the parser explicitly marked that it had an error
             //  b) any of it's children reported that it had an error.
-            var val = hasFlag(node.parserContextFlags, ParserContextFlags.ThisNodeHasError) ||
+            var thisNodeOrAnySubNodesHasError = hasFlag(node.parserContextFlags, ParserContextFlags.ThisNodeHasError) ||
                 forEachChild(node, containsParseError);
 
             // If so, mark ourselves accordingly. 
-            if (val) {
+            if (thisNodeOrAnySubNodesHasError) {
                 node.parserContextFlags |= ParserContextFlags.ThisNodeOrAnySubNodesHasError;
             }
 
             // Also mark that we've propogated the child information to this node.  This way we can
             // always consult the bit directly on this node without needing to check its children
             // again.
-            node.parserContextFlags |= ParserContextFlags.HasComputedThisNodeOrAnySubNodesHasError;
+            node.parserContextFlags |= ParserContextFlags.HasAggregatedChildData;
         }
-
-        return hasFlag(node.parserContextFlags, ParserContextFlags.ThisNodeOrAnySubNodesHasError);
     }
 
     export function getSourceFileOfNode(node: Node): SourceFile {