Support matrix multiplication operator (@) (#2287)

Closes #705.

mypy/fastparse.py

@@ -157,8 +157,6 @@ def from_operator(self, op: ast35.operator) -> str:
         op_name = ASTConverter.op_map.get(type(op))
         if op_name is None:
             raise RuntimeError('Unknown operator ' + str(type(op)))
-        elif op_name == '@':
-            raise RuntimeError('mypy does not support the MatMult operator')
         else:
             return op_name
 

mypy/lex.py

@@ -195,13 +195,13 @@ def lex(string: Union[str, bytes], first_line: int = 1,
 
 # List of regular expressions that match non-alphabetical operators
 operators = [re.compile('[-+*/<>.%&|^~]'),
-             re.compile('==|!=|<=|>=|\\*\\*|//|<<|>>|<>')]
+             re.compile('==|!=|<=|>=|\\*\\*|@|//|<<|>>|<>')]
 
 # List of regular expressions that match punctuator tokens
 punctuators = [re.compile('[=,()@`]|(->)'),
                re.compile('\\['),
                re.compile(']'),
-               re.compile('([-+*/%&|^]|\\*\\*|//|<<|>>)=')]
+               re.compile('([-+*/%@&|^]|\\*\\*|//|<<|>>)=')]
 
 
 # Map single-character string escape sequences to corresponding characters.

mypy/nodes.py

@@ -1328,6 +1328,7 @@ def accept(self, visitor: NodeVisitor[T]) -> T:
     '%': '__mod__',
     '//': '__floordiv__',
     '**': '__pow__',
+    '@': '__matmul__',
     '&': '__and__',
     '|': '__or__',
     '^': '__xor__',
@@ -1349,7 +1350,7 @@ def accept(self, visitor: NodeVisitor[T]) -> T:
 
 
 ops_with_inplace_method = {
-    '+', '-', '*', '/', '%', '//', '**', '&', '|', '^', '<<', '>>'}
+    '+', '-', '*', '/', '%', '//', '**', '@', '&', '|', '^', '<<', '>>'}
 
 inplace_operator_methods = set(
     '__i' + op_methods[op][2:] for op in ops_with_inplace_method)
@@ -1362,6 +1363,7 @@ def accept(self, visitor: NodeVisitor[T]) -> T:
     '__mod__': '__rmod__',
     '__floordiv__': '__rfloordiv__',
     '__pow__': '__rpow__',
+    '__matmul__': '__rmatmul__',
     '__and__': '__rand__',
     '__or__': '__ror__',
     '__xor__': '__rxor__',

mypy/parse.py

@@ -44,7 +44,7 @@
     '**': 16,
     '-u': 15, '+u': 15, '~': 15,   # unary operators (-, + and ~)
     '<cast>': 14,
-    '*': 13, '/': 13, '//': 13, '%': 13,
+    '*': 13, '/': 13, '//': 13, '%': 13, '@': 13,
     '+': 12, '-': 12,
     '>>': 11, '<<': 11,
     '&': 10,
@@ -61,7 +61,7 @@
 
 
 op_assign = set([
-    '+=', '-=', '*=', '/=', '//=', '%=', '**=', '|=', '&=', '^=', '>>=',
+    '+=', '-=', '*=', '/=', '//=', '%=', '**=', '@=', '|=', '&=', '^=', '>>=',
     '<<='])
 
 op_comp = set([

test-data/unit/check-expressions.test

@@ -182,6 +182,21 @@ main:3: error: Unsupported operand types for * ("A" and "C")
 main:4: error: Incompatible types in assignment (expression has type "C", variable has type "A")
 main:5: error: Unsupported left operand type for * ("B")
 
+[case testMatMul]
+a, b, c = None, None, None # type: (A, B, C)
+c = a @ c  # E: Unsupported operand types for @ ("A" and "C")
+a = a @ b  # E: Incompatible types in assignment (expression has type "C", variable has type "A")
+c = b @ a  # E: Unsupported left operand type for @ ("B")
+c = a @ b
+
+class A:
+    def __matmul__(self, x: 'B') -> 'C':
+        pass
+class B:
+    pass
+class C:
+    pass
+
 [case testDiv]
 
 a, b, c = None, None, None # type: (A, B, C)

test-data/unit/check-fastparse.test

@@ -179,3 +179,10 @@ def f(a):
     pass
 [out]
 main:3: error: invalid type comment
+
+[case testFastParseMatMul]
+# flags: --fast-parser
+from typing import Any
+x = None  # type: Any
+x @ 1
+x @= 1

test-data/unit/check-statements.test

@@ -228,6 +228,17 @@ class C: pass
 main:3: error: Unsupported operand types for * ("A" and "A")
 main:4: error: Unsupported left operand type for * ("C")
 
+[case testMatMulAssign]
+a, c = None, None # type: (A, C)
+a @= a   # E: Unsupported operand types for @ ("A" and "A")
+c @= a   # E: Unsupported left operand type for @ ("C")
+a @= c
+
+class A:
+    def __matmul__(self, x: 'C') -> 'A': pass
+
+class C: pass
+
 [case testDivAssign]
 
 a, c = None, None # type: (A, C)
@@ -295,11 +306,14 @@ import typing
 class A:
     def __iadd__(self, x: int) -> 'A': pass
     def __imul__(self, x: str) -> 'A': pass
+    def __imatmul__(self, x: str) -> 'A': pass
 a = A()
 a += 1
 a *= ''
+a @= ''
 a += '' # E: Argument 1 to "__iadd__" of "A" has incompatible type "str"; expected "int"
 a *= 1  # E: Argument 1 to "__imul__" of "A" has incompatible type "int"; expected "str"
+a @= 1  # E: Argument 1 to "__imatmul__" of "A" has incompatible type "int"; expected "str"
 
 [case testInplaceSetitem]
 class A(object):