[mypyc] Produce unimplemented errors on unsupported async features

And avoid triggering mypy assertion failures on errors.

Fixes #866.
Opened #868 to track the async feature work.

mypyc/codegen/emitmodule.py

@@ -407,6 +407,10 @@ def compile_modules_to_c(
     group_map = {source.module: lib_name for group, lib_name in groups for source in group}
     mapper = Mapper(group_map)
 
+    # Sometimes when we call back into mypy, there might be errors.
+    # We don't want to crash when that happens.
+    result.manager.errors.set_file('<mypyc>', module=None, scope=None)
+
     modules = compile_modules_to_ir(result, mapper, compiler_options, errors)
     ctext = compile_ir_to_c(groups, modules, result, mapper, compiler_options)
 

mypyc/irbuild/context.py

@@ -57,6 +57,10 @@ def namespaced_name(self) -> str:
     def is_generator(self) -> bool:
         return self.fitem.is_generator or self.fitem.is_coroutine
 
+    @property
+    def is_coroutine(self) -> bool:
+        return self.fitem.is_coroutine
+
     @property
     def callable_class(self) -> 'ImplicitClass':
         assert self._callable_class is not None

mypyc/irbuild/expression.py

@@ -659,14 +659,21 @@ def _visit_display(builder: IRBuilder,
 
 
 def transform_list_comprehension(builder: IRBuilder, o: ListComprehension) -> Value:
+    if any(o.generator.is_async):
+        builder.error('async comprehensions are unimplemented', o.line)
     return translate_list_comprehension(builder, o.generator)
 
 
 def transform_set_comprehension(builder: IRBuilder, o: SetComprehension) -> Value:
+    if any(o.generator.is_async):
+        builder.error('async comprehensions are unimplemented', o.line)
     return translate_set_comprehension(builder, o.generator)
 
 
 def transform_dictionary_comprehension(builder: IRBuilder, o: DictionaryComprehension) -> Value:
+    if any(o.is_async):
+        builder.error('async comprehensions are unimplemented', o.line)
+
     d = builder.call_c(dict_new_op, [], o.line)
     loop_params = list(zip(o.indices, o.sequences, o.condlists))
 
@@ -696,6 +703,9 @@ def get_arg(arg: Optional[Expression]) -> Value:
 
 
 def transform_generator_expr(builder: IRBuilder, o: GeneratorExpr) -> Value:
+    if any(o.is_async):
+        builder.error('async comprehensions are unimplemented', o.line)
+
     builder.warning('Treating generator comprehension as list', o.line)
     return builder.call_c(
         iter_op, [translate_list_comprehension(builder, o)], o.line

mypyc/irbuild/function.py

@@ -135,6 +135,9 @@ def transform_lambda_expr(builder: IRBuilder, expr: LambdaExpr) -> Value:
 
 
 def transform_yield_expr(builder: IRBuilder, expr: YieldExpr) -> Value:
+    if builder.fn_info.is_coroutine:
+        builder.error('async generators are unimplemented', expr.line)
+
     if expr.expr:
         retval = builder.accept(expr.expr)
     else:
@@ -143,6 +146,8 @@ def transform_yield_expr(builder: IRBuilder, expr: YieldExpr) -> Value:
 
 
 def transform_yield_from_expr(builder: IRBuilder, o: YieldFromExpr) -> Value:
+    if builder.fn_info.is_coroutine:
+        builder.error('async generators are unimplemented', expr.line)
     return handle_yield_from_and_await(builder, o)
 
 

mypyc/irbuild/statement.py

@@ -242,6 +242,9 @@ def transform_while_stmt(builder: IRBuilder, s: WhileStmt) -> None:
 
 
 def transform_for_stmt(builder: IRBuilder, s: ForStmt) -> None:
+    if s.is_async:
+        builder.error('async for is unimplemented', s.line)
+
     def body() -> None:
         builder.accept(s.body)
 
@@ -610,6 +613,9 @@ def finally_body() -> None:
 
 
 def transform_with_stmt(builder: IRBuilder, o: WithStmt) -> None:
+    if o.is_async:
+        builder.error('async with is unimplemented', o.line)
+
     # Generate separate logic for each expr in it, left to right
     def generate(i: int) -> None:
         if i >= len(o.expr):

mypyc/test-data/commandline.test

@@ -98,7 +98,7 @@ def f(x: int) -> int:
 # cmd: test.py
 
 [file test.py]
-from typing import List, Any
+from typing import List, Any, AsyncIterable
 from typing_extensions import Final
 from mypy_extensions import trait, mypyc_attr
 
@@ -192,3 +192,23 @@ class AllowInterp1(Concrete1):  # E: Base class "test.Concrete1" does not allow
 @mypyc_attr(allow_interpreted_subclasses=True)
 class AllowInterp2(PureTrait):  # E: Base class "test.PureTrait" does not allow interpreted subclasses
     pass
+
+async def async_for(xs: AsyncIterable[int]) -> None:
+    async for x in xs:  # E: async for is unimplemented
+        print(x)
+
+    [x async for x in xs]  # E: async comprehensions are unimplemented
+    (x async for x in xs)  # E: async comprehensions are unimplemented  # W: Treating generator comprehension as list
+    {x async for x in xs}  # E: async comprehensions are unimplemented
+    {x: x async for x in xs}  # E: async comprehensions are unimplemented
+
+class async_ctx:
+    async def __aenter__(self) -> int: pass
+    async def __aexit__(self, x, y, z) -> None: pass
+
+async def async_with() -> None:
+    async with async_ctx() as x:  # E: async with is unimplemented
+        print(x)
+
+async def async_generators() -> AsyncIterable[int]:
+    yield 1  # E: async generators are unimplemented