[mypyc] Translate attribute access to index access for named tuples (#…

…8665)

Fixes mypyc/mypyc#638

Previously `PyObject_GetAttr` was used for named tuples, which is slower.

mypy/semanal_namedtuple.py

@@ -376,6 +376,8 @@ def build_namedtuple_typeinfo(self,
         tuple_base = TupleType(types, fallback)
         info.tuple_type = tuple_base
         info.line = line
+        # For use by mypyc.
+        info.metadata['namedtuple'] = {'fields': items.copy()}
 
         # We can't calculate the complete fallback type until after semantic
         # analysis, since otherwise base classes might be incomplete. Postpone a

mypyc/irbuild/expression.py

@@ -13,6 +13,7 @@
     SetComprehension, DictionaryComprehension, SliceExpr, GeneratorExpr, CastExpr, StarExpr,
     Var, RefExpr, MypyFile, TypeInfo, TypeApplication, LDEF, ARG_POS
 )
+from mypy.types import TupleType, get_proper_type
 
 from mypyc.ir.ops import (
     Value, TupleGet, TupleSet, PrimitiveOp, BasicBlock, OpDescription, Assign
@@ -93,9 +94,15 @@ def transform_member_expr(builder: IRBuilder, expr: MemberExpr) -> Value:
         return builder.load_module(expr.node.fullname)
 
     obj = builder.accept(expr.expr)
-    return builder.builder.get_attr(
-        obj, expr.name, builder.node_type(expr), expr.line
-    )
+    rtype = builder.node_type(expr)
+    # Special case: for named tuples transform attribute access to faster index access.
+    typ = get_proper_type(builder.types.get(expr.expr))
+    if isinstance(typ, TupleType) and typ.partial_fallback.type.is_named_tuple:
+        fields = typ.partial_fallback.type.metadata['namedtuple']['fields']
+        if expr.name in fields:
+            index = builder.builder.load_static_int(fields.index(expr.name))
+            return builder.gen_method_call(obj, '__getitem__', [index], rtype, expr.line)
+    return builder.builder.get_attr(obj, expr.name, rtype, expr.line)
 
 
 def transform_super_expr(builder: IRBuilder, o: SuperExpr) -> Value:

mypyc/test-data/irbuild-tuple.test

@@ -162,3 +162,34 @@ L4:
     r8 = None
     return r8
 
+[case testNamedTupleAttribute]
+from typing import NamedTuple
+
+NT = NamedTuple('NT', [('x', int), ('y', int)])
+
+def f(nt: NT, b: bool) -> int:
+    if b:
+        return nt.x
+    return nt.y
+[out]
+def f(nt, b):
+    nt :: tuple
+    b :: bool
+    r0 :: short_int
+    r1 :: object
+    r2 :: int
+    r3 :: short_int
+    r4 :: object
+    r5 :: int
+L0:
+    if b goto L1 else goto L2 :: bool
+L1:
+    r0 = 0
+    r1 = nt[r0] :: tuple
+    r2 = unbox(int, r1)
+    return r2
+L2:
+    r3 = 1
+    r4 = nt[r3] :: tuple
+    r5 = unbox(int, r4)
+    return r5

mypyc/test-data/run.test

@@ -4741,3 +4741,24 @@ assert f("a", 16) == 10
 assert f("1a", 16) == 26
 with assertRaises(ValueError, "invalid literal for int() with base 10: 'xyz'"):
     f("xyz")
+
+[case testNamedTupleAttributeRun]
+from typing import NamedTuple
+
+NT = NamedTuple('NT', [('x', int), ('y', int)])
+
+def f(nt: NT) -> int:
+    if nt.x > nt.y:
+        return nt.x
+    return nt.y
+
+nt = NT(1, 2)
+[file driver.py]
+from native import NT, nt, f
+
+assert f(nt) == 2
+assert f(NT(3, 2)) == 3
+
+class Sub(NT):
+    pass
+assert f(Sub(3, 2)) == 3

mypyc/test/testutil.py

@@ -7,6 +7,8 @@
 import shutil
 from typing import List, Callable, Iterator, Optional, Tuple
 
+import pytest  # type: ignore[import]
+
 from mypy import build
 from mypy.errors import CompileError
 from mypy.options import Options
@@ -110,7 +112,9 @@ def build_ir_for_single_file(input_lines: List[str],
         [result.files['__main__']], result.graph, result.types,
         Mapper({'__main__': None}),
         compiler_options, errors)
-    assert errors.num_errors == 0
+    if errors.num_errors:
+        errors.flush_errors()
+        pytest.fail('Errors while building IR')
 
     module = list(modules.values())[0]
     return module.functions