Resolve '@' to '__matmul__' and '__rmatmul__' (PY-15390)

python/psi-api/src/com/jetbrains/python/PyTokenTypes.java

@@ -118,7 +118,7 @@ public class PyTokenTypes {
   public static final PyElementType RBRACKET = new PyElementType("RBRACKET");// ]
   public static final PyElementType LBRACE = new PyElementType("LBRACE");// {
   public static final PyElementType RBRACE = new PyElementType("RBRACE");// }
-  public static final PyElementType AT = new PyElementType("AT");// @
+  public static final PyElementType AT = new PyElementType("AT", "__matmul__");// @
   public static final PyElementType COMMA = new PyElementType("COMMA");// ,
   public static final PyElementType COLON = new PyElementType("COLON");// :
   public static final PyElementType DOT = new PyElementType("DOT");// .

python/testData/resolve/MatMul.py

@@ -0,0 +1,8 @@
+class C:
+    def __matmul__(self, other):
+        return self
+
+
+x = C()
+x @ y
+# <ref>

python/testData/resolve/RMatMul.py

@@ -0,0 +1,8 @@
+class C:
+    def __rmatmul__(self, other):
+        return self
+
+
+x = C()
+y @ x
+# <ref>

python/testSrc/com/jetbrains/python/PyResolveTest.java

@@ -571,4 +571,14 @@ public class PyResolveTest extends PyResolveTestCase {
   public void testResolveAttributesUsingOldStyleMROWhenUnresolvedAncestorsAndC3Fails() {
     assertResolvesTo(PyFunction.class, "foo");
   }
+
+  // PY-15390
+  public void testMatMul() {
+    assertResolvesTo(PyFunction.class, "__matmul__");
+  }
+
+  // PY-15390
+  public void testRMatMul() {
+    assertResolvesTo(PyFunction.class, "__rmatmul__");
+  }
 }