Use length hint when creating tuples

Fixes #756

Author: msimacek

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

@@ -1,4 +1,4 @@
-# Copyright (c) 2018, 2024, Oracle and/or its affiliates.
+# Copyright (c) 2018, 2026, Oracle and/or its affiliates.
 # Copyright (C) 1996-2017 Python Software Foundation
 #
 # Licensed under the PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
@@ -283,6 +283,38 @@ def maketuple(t):
         self.assertTrue(tuple(b) is b)
         self.assertFalse(tuple(a) is a)
 
+    def test_constructor_validates_length_hint_before_iteration(self):
+        class BadLengthHint:
+            def __getitem__(self, index):
+                raise AssertionError("__getitem__ should not be called")
+
+            def __length_hint__(self):
+                return None
+
+        with self.assertRaisesRegex(TypeError, "__length_hint__ must be an integer"):
+            tuple(BadLengthHint())
+
+    def test_constructor_validates_len_before_iteration(self):
+        class BadLen:
+            def __getitem__(self, index):
+                raise AssertionError("__getitem__ should not be called")
+
+            def __len__(self):
+                return -1
+
+        with self.assertRaisesRegex(ValueError, "__len__\\(\\) should return >= 0"):
+            tuple(BadLen())
+
+    def test_constructor_length_hint_too_small(self):
+        class SmallLengthHint:
+            def __iter__(self):
+                return iter((1, 2, 3))
+
+            def __length_hint__(self):
+                return 1
+
+        self.assertEqual(tuple(SmallLengthHint()), (1, 2, 3))
+
 
 class TupleCompareTest(CompareTest):
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/iterator/IteratorNodes.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -111,6 +111,7 @@ public abstract class IteratorNodes {
      */
     @GenerateInline
     @GenerateCached(false)
+    @GenerateUncached
     @ImportStatic({PGuards.class, SpecialMethodNames.class})
     public abstract static class GetLength extends PNodeWithContext {
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/builtins/TupleNodes.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -49,6 +49,7 @@
 import com.oracle.graal.python.builtins.objects.cext.structs.CStructAccess;
 import com.oracle.graal.python.builtins.objects.common.SequenceStorageNodes;
 import com.oracle.graal.python.builtins.objects.common.SequenceStorageNodes.CreateStorageFromIteratorNode;
+import com.oracle.graal.python.builtins.objects.iterator.IteratorNodes;
 import com.oracle.graal.python.builtins.objects.list.PList;
 import com.oracle.graal.python.builtins.objects.tuple.PTuple;
 import com.oracle.graal.python.lib.PyObjectGetIter;
@@ -101,10 +102,12 @@ static PTuple list(PList iterable,
         static PTuple generic(VirtualFrame frame, Object iterable,
                         @Bind Node inliningTarget,
                         @Bind PythonLanguage language,
+                        @Cached IteratorNodes.GetLength lenNode,
                         @Cached CreateStorageFromIteratorNode storageNode,
                         @Cached PyObjectGetIter getIter) {
+            int len = lenNode.execute(frame, inliningTarget, iterable);
             Object iterObj = getIter.execute(frame, inliningTarget, iterable);
-            return PFactory.createTuple(language, storageNode.execute(frame, iterObj));
+            return PFactory.createTuple(language, storageNode.execute(frame, iterObj, len));
         }
 
         @NeverDefault