Fix detection of export syntax in declaration file

index.ts

@@ -640,10 +640,7 @@ function getDtsExportKind(sourceFile: ts.SourceFile): InferenceResult<DtsExportK
     if (matches(sourceFile, isExportEquals)) {
         return inferenceSuccess(DtsExportKind.ExportEquals);
     }
-    if (matches(sourceFile, isExportConstruct)) {
-        return inferenceSuccess(DtsExportKind.ES6Like);
-    }
-    return inferenceError("Could not infer export kind of declaration file.");
+    return inferenceSuccess(DtsExportKind.ES6Like);
 }
 
 const exportEqualsSymbolName = "export=";
@@ -814,19 +811,6 @@ function isExportEquals(node: ts.Node): boolean {
     return ts.isExportAssignment(node) && !!node.isExportEquals;
 }
 
-function isExportConstruct(node: ts.Node): boolean {
-    return ts.isExportAssignment(node)
-        || ts.isExportDeclaration(node)
-        || hasExportModifier(node);
-}
-
-function hasExportModifier(node: ts.Node): boolean {
-    if (node.modifiers) {
-        return node.modifiers.some(modifier => modifier.kind === ts.SyntaxKind.ExportKeyword);
-    }
-    return false;
-}
-
 function matches(srcFile: ts.SourceFile, predicate: (n: ts.Node) => boolean): boolean {
     function matchesNode(node: ts.Node): boolean {
         if (predicate(node)) return true;