Address minor PR comment

Author: Yui T

src/compiler/checker.ts

@@ -17134,10 +17134,11 @@ namespace ts {
                 case SyntaxKind.ElementAccessExpression:
                     return checkIndexedAccess(<ElementAccessExpression>node);
                 case SyntaxKind.CallExpression:
-                case SyntaxKind.NewExpression:
                     if ((<CallExpression>node).expression.kind === SyntaxKind.ImportKeyword) {
                         return checkImportCallExpression(<ImportCall>node);
                     }
+                    // Fall through
+                case SyntaxKind.NewExpression:
                     return checkCallExpression(<CallExpression>node);
                 case SyntaxKind.TaggedTemplateExpression:
                     return checkTaggedTemplateExpression(<TaggedTemplateExpression>node);

src/compiler/parser.ts

@@ -2416,7 +2416,7 @@ namespace ts {
             if (token() === SyntaxKind.OpenParenToken || token() === SyntaxKind.LessThanToken) {
                 return parseSignatureMember(SyntaxKind.CallSignature);
             }
-            if (token() === SyntaxKind.NewKeyword && lookAhead(isStartOfConstructSignature)) {
+            if (token() === SyntaxKind.NewKeyword && lookAhead(nextTokenIsOpenParenOrLessThan)) {
                 return parseSignatureMember(SyntaxKind.ConstructSignature);
             }
             const fullStart = getNodePos();
@@ -2427,7 +2427,7 @@ namespace ts {
             return parsePropertyOrMethodSignature(fullStart, modifiers);
         }
 
-        function isStartOfConstructSignature() {
+        function nextTokenIsOpenParenOrLessThan() {
             nextToken();
             return token() === SyntaxKind.OpenParenToken || token() === SyntaxKind.LessThanToken;
         }
@@ -5619,11 +5619,6 @@ namespace ts {
             return nextToken() === SyntaxKind.OpenParenToken;
         }
 
-        function nextTokenIsOpenParenOrLessThan() {
-            const next = nextToken();
-            return next === SyntaxKind.OpenParenToken || next === SyntaxKind.LessThanToken;
-        }
-
         function nextTokenIsSlash() {
             return nextToken() === SyntaxKind.SlashToken;
         }

src/compiler/program.ts

@@ -1199,6 +1199,10 @@ namespace ts {
         }
 
         function collectExternalModuleReferences(file: SourceFile): void {
+            if (file.imports) {
+                return;
+            }
+
             const isJavaScriptFile = isSourceFileJavaScript(file);
             const isExternalModuleFile = isExternalModule(file);
             const isDtsFile = isDeclarationFile(file);