phpnode
diff --git a/‎src/compiler/emitter.ts‎
Lines changed: 23 additions & 6 deletions b/‎src/compiler/emitter.ts‎
Lines changed: 23 additions & 6 deletions
@@ -19,6 +19,8 @@ module ts {
         return isExternalModule(sourceFile) || isDeclarationFile(sourceFile);
     }
 
+    // flag enum used to request and track usages of few dedicated temp variables
+    // enum values are used to set/check bit values and thus should not have bit collisions.
     const enum TempVariableKind {
         auto = 0,
         _i = 1,
@@ -216,7 +218,7 @@ module ts {
             //     _i;
             // }
             // we should be able to detect if let _i was shadowed by some temp variable that was allocated in scope
-            function hasConflictsWithTempVariables(name: string): boolean {
+            function nameConflictsWithSomeTempVariable(name: string): boolean {
                 // temp variable names always start with '_'
                 if (name.length < 2 || name.charCodeAt(0) !== CharacterCodes._) {
                     return false;
@@ -242,7 +244,12 @@ module ts {
                 }
             }
 
+            // This function generates a name using the following pattern:
             // _a .. _h, _j ... _z, _0, _1, ...
+            // It is guaranteed that generated name will not shadow any existing user-defined names,
+            // however it can hide another name generated by this function higher in the scope.
+            // NOTE: names generated by 'makeTempVariableName' and 'makeUniqueName' will never conflict.
+            // see comment for 'makeTempVariableName' for more information.
             function makeTempVariableName(location: Node, tempVariableKind: TempVariableKind): string {
                 let tempName: string;
                 if (tempVariableKind !== TempVariableKind.auto && !(predefinedTempsInUse & tempVariableKind)) {
@@ -272,8 +279,17 @@ module ts {
                 return tempName;
             }
 
-            // unique names always end with _<number>
-            // generated unique names: name_1, name_2...
+            // Generates a name that is unique within current file and does not collide with
+            // any names in global scope.
+            // NOTE: names generated by 'makeTempVariableName' and 'makeUniqueName' will never conflict
+            // because of the way how these names are generated
+            // - makeUniqueName builds a name by picking a base name (which should not be empty string)
+            //   and appending suffix '_<number>'
+            // - makeTempVariableName creates a name using the following pattern:
+            //   _a .. _h, _j ... _z, _0, _1, ...
+            // This means that names from 'makeTempVariableName' will have only one underscore at the beginning
+            // and names from 'makeUniqieName' will have at least one underscore in the middle 
+            // so they will never collide.
             function makeUniqueName(baseName: string): string {
                 Debug.assert(!!baseName);
 
@@ -2787,8 +2803,9 @@ module ts {
                 let list = getAncestor(node, SyntaxKind.VariableDeclarationList);
                 if (list.parent.kind === SyntaxKind.VariableStatement) {
                     let isSourceFileLevelBinding = list.parent.parent.kind === SyntaxKind.SourceFile;
-                    let isModuleLevelBinding = list.parent.parent.kind === SyntaxKind.ModuleDeclaration;
-                    let isFunctionLevelBinding = isFunctionLike(list.parent.parent);
+                    let isModuleLevelBinding = list.parent.parent.kind === SyntaxKind.ModuleBlock;
+                    let isFunctionLevelBinding =
+                        list.parent.parent.kind === SyntaxKind.Block && isFunctionLike(list.parent.parent.parent);
                     if (isSourceFileLevelBinding || isModuleLevelBinding || isFunctionLevelBinding) {
                         return;
                     }
@@ -2801,7 +2818,7 @@ module ts {
 
                 var hasConflictsInEnclosingScope =
                     !resolver.isUnknownIdentifier(parent, (<Identifier>node).text) ||
-                    hasConflictsWithTempVariables((<Identifier>node).text);
+                    nameConflictsWithSomeTempVariable((<Identifier>node).text);
 
                 if (hasConflictsInEnclosingScope) {
                     let variableId = resolver.getBlockScopedVariableId(<Identifier>node);