type as type

Summary:
```
isinstance(list[str], type) # True
isinstance(1, type)         # False
```

Python [allows `type` function used as type](https://docs.python.org/3/library/typing.html#the-type-of-class-objects).

Antlir uses types in function signatures by (incorrectly) enumerating all possibilities.

But this is done in preparation to remove `Ty::name`.

Reviewed By: ianlevesque

Differential Revision: D48936317

fbshipit-source-id: 28622cbaf348a322095a01b8cc2f5bdf2f6994b6

Author: stepancheg

starlark/src/stdlib/funcs/other.rs

@@ -44,6 +44,7 @@ use crate::values::tuple::TupleRef;
 use crate::values::types::int_or_big::StarlarkInt;
 use crate::values::types::int_or_big::StarlarkIntRef;
 use crate::values::typing::never::StarlarkNever;
+use crate::values::typing::ty::AbstractType;
 use crate::values::typing::StarlarkIter;
 use crate::values::value_of_unchecked::ValueOfUnchecked;
 use crate::values::AllocValue;
@@ -862,7 +863,7 @@ pub(crate) fn register_other(builder: &mut GlobalsBuilder) {
     /// type("hello")           == "string"
     /// # "#);
     /// ```
-    #[starlark(speculative_exec_safe)]
+    #[starlark(speculative_exec_safe, as_type = AbstractType)]
     fn r#type<'v>(#[starlark(require = pos)] a: Value) -> anyhow::Result<FrozenStringValue> {
         Ok(a.get_type_value())
     }

starlark/src/tests/docs/rustdocs.rs

@@ -17,41 +17,59 @@
 
 use std::collections::HashMap;
 
+use allocative::Allocative;
 use starlark_derive::starlark_module;
+use starlark_derive::starlark_value;
+use starlark_derive::NoSerialize;
+use starlark_derive::ProvidesStaticType;
 use starlark_map::small_map::SmallMap;
 
 use crate as starlark;
-use crate::assert;
+use crate::assert::Assert;
 use crate::docs::DocItem;
 use crate::docs::DocMember;
 use crate::environment::GlobalsBuilder;
 use crate::eval::Arguments;
 use crate::eval::Evaluator;
-use crate::typing::Ty;
 use crate::values::none::NoneType;
-use crate::values::type_repr::StarlarkTypeRepr;
+use crate::values::starlark_value_as_type::StarlarkValueAsType;
 use crate::values::Heap;
+use crate::values::StarlarkValue;
 use crate::values::StringValue;
 use crate::values::Value;
 use crate::values::ValueOfUnchecked;
 
+#[derive(
+    Debug,
+    derive_more::Display,
+    Allocative,
+    NoSerialize,
+    ProvidesStaticType
+)]
+#[display(fmt = "input")]
 struct InputTypeRepr;
+#[derive(
+    Debug,
+    derive_more::Display,
+    Allocative,
+    NoSerialize,
+    ProvidesStaticType
+)]
+#[display(fmt = "output")]
 struct OutputTypeRepr;
 
-impl StarlarkTypeRepr for InputTypeRepr {
-    fn starlark_type_repr() -> Ty {
-        Ty::name_static("input")
-    }
-}
-impl StarlarkTypeRepr for OutputTypeRepr {
-    fn starlark_type_repr() -> Ty {
-        Ty::name_static("output")
-    }
-}
+#[starlark_value(type = "input")]
+impl<'v> StarlarkValue<'v> for InputTypeRepr {}
+
+#[starlark_value(type = "output")]
+impl<'v> StarlarkValue<'v> for OutputTypeRepr {}
 
 #[starlark_module]
 #[allow(unused_variables)] // Since this is for a test
 fn globals(builder: &mut GlobalsBuilder) {
+    const Input: StarlarkValueAsType<InputTypeRepr> = StarlarkValueAsType::new();
+    const Output: StarlarkValueAsType<OutputTypeRepr> = StarlarkValueAsType::new();
+
     fn simple(
         arg_int: i32,
         arg_bool: bool,
@@ -97,18 +115,18 @@ fn globals(builder: &mut GlobalsBuilder) {
 #[test]
 fn test_rustdoc() {
     let got = GlobalsBuilder::new().with(globals).build();
-    let expected = assert::pass_module(
-        r#"
+    let mut a = Assert::new();
+    a.globals_add(globals);
+    let expected = a.pass_module(r#"
 # @starlark-rust: allow_string_literals_in_type_expr
 
 def args_kwargs(*args, **kwargs: typing.Any) -> None: pass
-def custom_types(arg1: str, arg2: "input") -> "output": pass
+def custom_types(arg1: str, arg2: Input) -> Output: pass
 def default_arg(arg1 = "_", arg2: typing.Any = None) -> list[str]: pass
 def pos_named(arg1: int, *, arg2: int) -> int: pass
 def simple(arg_int: int, arg_bool: bool, arg_vec: list[str], arg_dict: dict[str, (bool, int)]) -> None: pass
 def with_arguments(*args, **kwargs) -> int: pass
-"#,
-    );
+"#);
 
     fn unpack(x: DocItem) -> HashMap<String, DocItem> {
         match x {

starlark/src/typing/basic.rs

@@ -50,6 +50,8 @@ pub enum TyBasic {
     Iter(ArcTy),
     /// `typing.Callable`.
     Callable,
+    /// `type`.
+    Type,
     /// A list.
     List(ArcTy),
     /// A tuple. May be empty, to indicate the empty tuple.
@@ -120,6 +122,7 @@ impl TyBasic {
             TyBasic::List(_) => Some("list"),
             TyBasic::Tuple(_) => Some("tuple"),
             TyBasic::Dict(..) => Some("dict"),
+            TyBasic::Type => Some("type"),
             TyBasic::Custom(c) => c.as_name(),
             TyBasic::Any | TyBasic::Iter(_) | TyBasic::Callable => None,
         }
@@ -169,6 +172,7 @@ impl Display for TyBasic {
             TyBasic::List(x) => write!(f, "list[{}]", x),
             TyBasic::Tuple(tuple) => Display::fmt(tuple, f),
             TyBasic::Dict(k, v) => write!(f, "dict[{}, {}]", k, v),
+            TyBasic::Type => write!(f, "type"),
             TyBasic::Custom(c) => Display::fmt(c, f),
         }
     }

starlark/src/typing/oracle/ctx.rs

@@ -296,7 +296,7 @@ impl<'a> TypingOracleCtx<'a> {
                         ty: fun.to_string(),
                     },
                 )),
-            TyBasic::Iter(_) => {
+            TyBasic::Iter(_) | TyBasic::Type => {
                 // Unknown type, may be callable.
                 Ok(Ty::any())
             }
@@ -349,6 +349,7 @@ impl<'a> TypingOracleCtx<'a> {
             TyBasic::Dict(k, _v) => Ok((**k).dupe()),
             TyBasic::Tuple(tuple) => Ok(tuple.item_ty()),
             TyBasic::Callable => Ok(Ty::any()),
+            TyBasic::Type => Ok(Ty::any()),
             TyBasic::Iter(ty) => Ok(ty.to_ty()),
             TyBasic::Custom(ty) => ty.0.iter_item_dyn(),
             TyBasic::Name(_) => Ok(Ty::any()),
@@ -374,7 +375,9 @@ impl<'a> TypingOracleCtx<'a> {
         index: Spanned<&TyBasic>,
     ) -> Result<Result<Ty, ()>, InternalError> {
         match array {
-            TyBasic::Any | TyBasic::Callable | TyBasic::Iter(_) => Ok(Ok(Ty::any())),
+            TyBasic::Any | TyBasic::Callable | TyBasic::Iter(_) | TyBasic::Type => {
+                Ok(Ok(Ty::any()))
+            }
             TyBasic::Tuple(tuple) => {
                 if !self.intersects_basic(index.node, &TyBasic::int()) {
                     return Ok(Err(()));
@@ -467,7 +470,7 @@ impl<'a> TypingOracleCtx<'a> {
 
     fn expr_dot_basic(&self, array: &TyBasic, attr: &str) -> Result<Ty, ()> {
         match array {
-            TyBasic::Any | TyBasic::Callable | TyBasic::Iter(_) => Ok(Ty::any()),
+            TyBasic::Any | TyBasic::Callable | TyBasic::Iter(_) | TyBasic::Type => Ok(Ty::any()),
             TyBasic::StarlarkValue(s) => s.attr(attr),
             TyBasic::Tuple(_) => Err(()),
             TyBasic::List(elem) => match attr {
@@ -567,7 +570,7 @@ impl<'a> TypingOracleCtx<'a> {
         rhs: Spanned<&TyBasic>,
     ) -> Result<Ty, ()> {
         match lhs {
-            TyBasic::Any | TyBasic::Iter(_) | TyBasic::Callable => Ok(Ty::any()),
+            TyBasic::Any | TyBasic::Iter(_) | TyBasic::Callable | TyBasic::Type => Ok(Ty::any()),
             TyBasic::StarlarkValue(lhs) => lhs.bin_op(bin_op, rhs.node),
             lhs @ TyBasic::List(elem) => match bin_op {
                 TypingBinOp::Less => {
@@ -846,6 +849,11 @@ impl<'a> TypingOracleCtx<'a> {
                 Err(()) => false,
             },
             (TyBasic::Custom(x), y) => x.intersects_with(y),
+            (TyBasic::Type, TyBasic::StarlarkValue(y)) => y.is_type(),
+            (TyBasic::Type, _) => {
+                // TODO(nga): more precise.
+                true
+            }
             (x, y) if x.is_function() && y.is_function() => true,
             // There are lots of other cases that overlap, but add them as we need them
             _ => false,

starlark/src/typing/starlark_value.rs

@@ -273,6 +273,17 @@ impl TyStarlarkValue {
         vtable.HAS_iterate || vtable.HAS_iterate_collect
     }
 
+    /// Instance of this type can be evaluated as a type.
+    #[inline]
+    pub(crate) fn is_type_from_vtable(vtable: &StarlarkValueVTable) -> bool {
+        vtable.HAS_eval_type
+    }
+
+    pub(crate) fn is_type(self) -> bool {
+        self.self_check();
+        Self::is_type_from_vtable(&self.vtable.vtable)
+    }
+
     pub(crate) fn iter_item(self) -> Result<Ty, ()> {
         if Self::is_iterable(&self.vtable.vtable) {
             Ok(Ty::any())

starlark/src/typing/ty.rs

@@ -135,10 +135,6 @@ impl TyName {
         TyName(s.into())
     }
 
-    pub(crate) fn new_static(s: &'static str) -> TyName {
-        TyName(ArcStr::new_static(s))
-    }
-
     /// Get the underlying `str` for a `TyName`.
     pub fn as_str(&self) -> &str {
         &self.0
@@ -190,15 +186,6 @@ impl Ty {
         }
     }
 
-    /// Create a [`Ty::Name`], or one of the standard functions.
-    pub(crate) fn name_static(name: &'static str) -> Self {
-        if let Some(x) = Self::try_name_special(name) {
-            x
-        } else {
-            Ty::basic(TyBasic::Name(TyName::new_static(name)))
-        }
-    }
-
     pub(crate) fn name(name: &str) -> Self {
         if let Some(x) = Self::try_name_special(name) {
             x

starlark/src/values/types/starlark_value_as_type.rs

@@ -35,6 +35,7 @@ use crate::values::layout::avalue::AValueImpl;
 use crate::values::layout::avalue::Basic;
 use crate::values::layout::heap::repr::AValueRepr;
 use crate::values::type_repr::StarlarkTypeRepr;
+use crate::values::typing::ty::AbstractType;
 use crate::values::AllocFrozenValue;
 use crate::values::FrozenHeap;
 use crate::values::FrozenValue;
@@ -45,6 +46,8 @@ struct StarlarkValueAsTypeStarlarkValue(fn() -> Ty);
 
 #[starlark_value(type = "type")]
 impl<'v> StarlarkValue<'v> for StarlarkValueAsTypeStarlarkValue {
+    type Canonical = AbstractType;
+
     fn eval_type(&self) -> Option<Ty> {
         Some((self.0)())
     }
@@ -118,8 +121,7 @@ impl<T: StarlarkTypeRepr> Default for StarlarkValueAsType<T> {
 
 impl<T: StarlarkTypeRepr> StarlarkTypeRepr for StarlarkValueAsType<T> {
     fn starlark_type_repr() -> Ty {
-        // TODO(nga): make it proper type.
-        Ty::name_static("type")
+        AbstractType::starlark_type_repr()
     }
 }
 

starlark/src/values/typing/mod.rs

@@ -23,6 +23,7 @@ pub(crate) mod globals;
 pub(crate) mod iter;
 pub mod macro_refs;
 pub(crate) mod never;
+pub(crate) mod ty;
 pub(crate) mod type_compiled;
 
 pub use crate::values::types::type_instance_id::TypeInstanceId;

starlark/src/values/typing/ty.rs

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2019 The Starlark in Rust Authors.
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use allocative::Allocative;
+use starlark_derive::starlark_value;
+use starlark_derive::NoSerialize;
+use starlark_derive::ProvidesStaticType;
+
+use crate as starlark;
+use crate::typing::Ty;
+use crate::typing::TyBasic;
+use crate::values::StarlarkValue;
+
+/// Type of type.
+#[derive(
+    Debug,
+    derive_more::Display,
+    Allocative,
+    ProvidesStaticType,
+    NoSerialize
+)]
+#[display(fmt = "type")]
+#[allocative(skip)] // TODO(nga): derive.
+pub enum AbstractType {}
+
+#[starlark_value(type = "type")]
+impl<'v> StarlarkValue<'v> for AbstractType {
+    fn get_type_starlark_repr() -> Ty {
+        Ty::basic(TyBasic::Type)
+    }
+
+    fn eval_type(&self) -> Option<Ty> {
+        unreachable!(
+            "This is unreachable, but this function is needed \
+            so `TyStarlarkValue` could think this is a type"
+        )
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::assert;
+
+    #[test]
+    fn test_isinstance() {
+        assert::is_true("isinstance(int, type)");
+        assert::is_false("isinstance(1, type)");
+        assert::is_true("isinstance(list[str], type)");
+        assert::is_true("isinstance(eval_type(list), type)");
+    }
+
+    #[test]
+    fn test_pass() {
+        assert::pass(
+            r#"
+def accepts_type(t: type):
+    pass
+
+def test():
+    accepts_type(int)
+    accepts_type(list[str])
+    accepts_type(None | int)
+
+test()
+"#,
+        );
+    }
+
+    #[test]
+    fn test_fail_compile_time() {
+        assert::fail(
+            r#"
+def accepts_type(t: type):
+    pass
+
+def test():
+    accepts_type(1)
+"#,
+            "Expected type `type` but got `int`",
+        );
+    }
+}

starlark/src/values/typing/type_compiled/alloc.rs

@@ -39,6 +39,7 @@ use crate::values::typing::type_compiled::matchers::IsName;
 use crate::values::typing::type_compiled::matchers::IsNever;
 use crate::values::typing::type_compiled::matchers::IsNone;
 use crate::values::typing::type_compiled::matchers::IsStr;
+use crate::values::typing::type_compiled::matchers::IsType;
 use crate::values::typing::type_compiled::matchers::StarlarkTypeIdMatcher;
 use crate::values::typing::type_compiled::type_matcher_factory::TypeMatcherFactory;
 
@@ -147,6 +148,7 @@ pub trait TypeMatcherAlloc: Sized {
             TyBasic::Dict(k, v) => self.dict_of(k, v),
             TyBasic::Iter(_item) => self.alloc(IsIterable),
             TyBasic::Callable => self.alloc(IsCallable),
+            TyBasic::Type => self.alloc(IsType),
             TyBasic::Custom(custom) => self.custom(custom),
         }
     }