[GR-9814] fix lambda def arglist parsing when no args are specified

PullRequest: graalpython-open/51

Author: cosminbasca

graalpython/com.oracle.graal.python.test/src/tests/test_parser.py

@@ -63,3 +63,12 @@ def x(*, a=None, b):
 retval = x(b=42)
     """, globs)
     assert globs["retval"] == (None, 42)
+
+
+def test_lambda_no_args_with_nested_lambdas():
+    no_err = True
+    try:
+        eval("lambda: ((lambda args: args[0], ), (lambda args: args[1], ), )")
+    except Exception as e:
+        no_err = False
+    assert no_err

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/ScopeTranslator.java

@@ -155,7 +155,9 @@ public T visitLambdef_nocond_body(Python3Parser.Lambdef_nocond_bodyContext ctx)
     @Override
     public T visitLambdef(Python3Parser.LambdefContext ctx) {
         argListCompilers.push(new ArgListCompiler<>(core));
-        ctx.accept(argListCompilers.peek());
+        if (ctx.varargslist() != null) {
+            ctx.accept(argListCompilers.peek());
+        }
         environment.beginScope(ctx, ScopeKind.Function);
         try {
             return super.visitLambdef(ctx);