PY-20063 Fixed: Code introspection / autocomplete does not resolve types in Sets (and perhaps other collection types) when used with single-character iteration expressions

Add skeletons for set.__iter__

python/helpers/python-skeletons/__builtin__.py

@@ -2349,6 +2349,12 @@ class set(object):
         """
         return False
 
+    def __iter__(self):
+        """
+        :rtype: collections.Iterator[T]
+        """
+        pass
+
 
 class frozenset(object):
     """frozenset object."""

python/helpers/python-skeletons/builtins.py

@@ -2039,6 +2039,12 @@ class set(object):
         """
         return False
 
+    def __iter__(self):
+        """
+        :rtype: collections.Iterator[T]
+        """
+        pass
+
 
 class frozenset(object):
     """frozenset object."""

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

@@ -1102,6 +1102,14 @@ public class PyTypeTest extends PyTestCase {
            TypeEvalContext.userInitiated(expr.getProject(), expr.getContainingFile()));
   }
 
+  // PY-20063
+  public void testIteratedSetElement() {
+    doTest("int",
+           "xs = {1}\n" +
+           "for expr in xs:\n" +
+           "    print(expr)");
+  }
+
   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());