diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index b620be2ed5e..e35c5a08297 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -1708,6 +1708,9 @@ namespace ts {
         return nodes;
     }
 
+    /**
+     * Get the name of that target module from an import or export declaration
+     */
     export function getLocalNameForExternalImport(node: ImportDeclaration | ExportDeclaration | ImportEqualsDeclaration, sourceFile: SourceFile): Identifier {
         const namespaceDeclaration = getNamespaceDeclarationNode(node);
         if (namespaceDeclaration && !isDefaultImport(node)) {
@@ -1719,8 +1722,17 @@ namespace ts {
         if (node.kind === SyntaxKind.ExportDeclaration && (<ExportDeclaration>node).moduleSpecifier) {
             return getGeneratedNameForNode(node);
         }
+        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>" />
+     *  2. --out or --outFile is used, making the name relative to the rootDir
+     *  3- The containing SourceFile has an entry in renamedDependencies for the import as requested by some module loaders (e.g. System).
+     * Otherwise, a new StringLiteral node representing the module name will be returned.
+     */
     export function getExternalModuleNameLiteral(importNode: ImportDeclaration | ExportDeclaration | ImportEqualsDeclaration, sourceFile: SourceFile, host: EmitHost, resolver: EmitResolver, compilerOptions: CompilerOptions) {
         const moduleName = getExternalModuleName(importNode);
         if (moduleName.kind === SyntaxKind.StringLiteral) {
@@ -1743,6 +1755,13 @@ namespace ts {
         return undefined;
     }
 
+    /**
+     * Get the name of a module 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>" />
+     *  2. --out or --outFile is used, making the name relative to the rootDir
+     * Otherwise, a new StringLiteral node representing the module name will be returned.
+     */
     export function tryGetModuleNameFromFile(file: SourceFile, host: EmitHost, options: CompilerOptions): StringLiteral {
         if (!file) {
             return undefined;