PY-21692 Fixed: Return type of sum(List[Decimal]) is 'Any' (should be 'Decimal')

Add skeletons for builtin sum function

python/helpers/python-skeletons/__builtin__.py

@@ -229,6 +229,16 @@ def max(*args, key=None, default=None):
     pass
 
 
+def sum(iterable, start=0):
+    """Sums start and the items of an iterable from left to right and returns
+    the total.
+
+    :type iterable: collections.Iterable[T]
+    :rtype: T
+    """
+    pass
+
+
 def next(iterator, default=None):
     """Return the next item from the iterator.
 

python/helpers/python-skeletons/builtins.py

@@ -232,6 +232,16 @@ def max(*args, key=None, default=None):
     pass
 
 
+def sum(iterable, start=0):
+    """Sums start and the items of an iterable from left to right and returns
+    the total.
+
+    :type iterable: collections.Iterable[T]
+    :rtype: T
+    """
+    pass
+
+
 def next(iterator, default=None):
     """Return the next item from the iterator.
 

python/testSrc/com/jetbrains/python/Py3TypeTest.java

@@ -475,6 +475,12 @@ public class Py3TypeTest extends PyTestCase {
            "expr = max(1, 2, 3)");
   }
 
+  // PY-21692
+  public void testSumResult() {
+    doTest("int",
+           "expr = sum([1, 2, 3])");
+  }
+
   private void doTest(final String expectedType, final String text) {
     myFixture.configureByText(PythonFileType.INSTANCE, text);
     final PyExpression expr = myFixture.findElementByText("expr", PyExpression.class);

python/testSrc/com/jetbrains/python/PyTypeTest.java

@@ -1524,6 +1524,12 @@ public class PyTypeTest extends PyTestCase {
            "expr = max(1, 2, 3)");
   }
 
+  // PY-21692
+  public void testSumResult() {
+    doTest("int",
+           "expr = sum([1, 2, 3])");
+  }
+
   private static List<TypeEvalContext> getTypeEvalContexts(@NotNull PyExpression element) {
     return ImmutableList.of(TypeEvalContext.codeAnalysis(element.getProject(), element.getContainingFile()).withTracing(),
                             TypeEvalContext.userInitiated(element.getProject(), element.getContainingFile()).withTracing());