Support computing layout of RPIT

crates/hir-ty/src/chalk_db.rs

@@ -205,7 +205,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
                     .return_type_impl_traits(func)
                     .expect("impl trait id without impl traits");
                 let (datas, binders) = (*datas).as_ref().into_value_and_skipped_binders();
-                let data = &datas.impl_traits[idx as usize];
+                let data = &datas.impl_traits[idx];
                 let bound = OpaqueTyDatumBound {
                     bounds: make_single_type_binders(data.bounds.skip_binders().to_vec()),
                     where_clauses: chalk_ir::Binders::empty(Interner, vec![]),

crates/hir-ty/src/chalk_ext.rs

@@ -234,9 +234,8 @@ impl TyExt for Ty {
                     }
                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
                         db.return_type_impl_traits(func).map(|it| {
-                            let data = (*it)
-                                .as_ref()
-                                .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
+                            let data =
+                                (*it).as_ref().map(|rpit| rpit.impl_traits[idx].bounds.clone());
                             data.substitute(Interner, &subst).into_value_and_skipped_binders().0
                         })
                     }
@@ -247,9 +246,8 @@ impl TyExt for Ty {
                 {
                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
                         db.return_type_impl_traits(func).map(|it| {
-                            let data = (*it)
-                                .as_ref()
-                                .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
+                            let data =
+                                (*it).as_ref().map(|rpit| rpit.impl_traits[idx].bounds.clone());
                             data.substitute(Interner, &opaque_ty.substitution)
                         })
                     }

crates/hir-ty/src/display.rs

@@ -458,9 +458,8 @@ impl HirDisplay for Ty {
                             let datas = db
                                 .return_type_impl_traits(func)
                                 .expect("impl trait id without data");
-                            let data = (*datas)
-                                .as_ref()
-                                .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
+                            let data =
+                                (*datas).as_ref().map(|rpit| rpit.impl_traits[idx].bounds.clone());
                             let bounds = data.substitute(Interner, parameters);
                             let mut len = bounds.skip_binders().len();
 
@@ -718,9 +717,8 @@ impl HirDisplay for Ty {
                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
                         let datas =
                             db.return_type_impl_traits(func).expect("impl trait id without data");
-                        let data = (*datas)
-                            .as_ref()
-                            .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
+                        let data =
+                            (*datas).as_ref().map(|rpit| rpit.impl_traits[idx].bounds.clone());
                         let bounds = data.substitute(Interner, &parameters);
                         let krate = func.lookup(db.upcast()).module(db.upcast()).krate();
                         write_bounds_like_dyn_trait_with_prefix(
@@ -828,9 +826,8 @@ impl HirDisplay for Ty {
                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
                         let datas =
                             db.return_type_impl_traits(func).expect("impl trait id without data");
-                        let data = (*datas)
-                            .as_ref()
-                            .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
+                        let data =
+                            (*datas).as_ref().map(|rpit| rpit.impl_traits[idx].bounds.clone());
                         let bounds = data.substitute(Interner, &opaque_ty.substitution);
                         let krate = func.lookup(db.upcast()).module(db.upcast()).krate();
                         write_bounds_like_dyn_trait_with_prefix(

crates/hir-ty/src/infer.rs

@@ -39,7 +39,7 @@ use stdx::always;
 use crate::{
     db::HirDatabase, fold_tys, fold_tys_and_consts, infer::coerce::CoerceMany,
     lower::ImplTraitLoweringMode, to_assoc_type_id, AliasEq, AliasTy, Const, DomainGoal,
-    GenericArg, Goal, ImplTraitId, InEnvironment, Interner, ProjectionTy, Substitution,
+    GenericArg, Goal, ImplTraitId, InEnvironment, Interner, ProjectionTy, RpitId, Substitution,
     TraitEnvironment, TraitRef, Ty, TyBuilder, TyExt, TyKind,
 };
 
@@ -352,6 +352,7 @@ pub struct InferenceResult {
     /// **Note**: When a pattern type is resolved it may still contain
     /// unresolved or missing subpatterns or subpatterns of mismatched types.
     pub type_of_pat: ArenaMap<PatId, Ty>,
+    pub type_of_rpit: ArenaMap<RpitId, Ty>,
     type_mismatches: FxHashMap<ExprOrPatId, TypeMismatch>,
     /// Interned common types to return references to.
     standard_types: InternedStandardTypes,
@@ -525,6 +526,9 @@ impl<'a> InferenceContext<'a> {
         for ty in result.type_of_pat.values_mut() {
             *ty = table.resolve_completely(ty.clone());
         }
+        for ty in result.type_of_rpit.iter_mut().map(|x| x.1) {
+            *ty = table.resolve_completely(ty.clone());
+        }
         for mismatch in result.type_mismatches.values_mut() {
             mismatch.expected = table.resolve_completely(mismatch.expected.clone());
             mismatch.actual = table.resolve_completely(mismatch.actual.clone());
@@ -603,7 +607,7 @@ impl<'a> InferenceContext<'a> {
                         _ => unreachable!(),
                     };
                     let bounds = (*rpits).map_ref(|rpits| {
-                        rpits.impl_traits[idx as usize].bounds.map_ref(|it| it.into_iter())
+                        rpits.impl_traits[idx].bounds.map_ref(|it| it.into_iter())
                     });
                     let var = self.table.new_type_var();
                     let var_subst = Substitution::from1(Interner, var.clone());
@@ -616,6 +620,7 @@ impl<'a> InferenceContext<'a> {
                         always!(binders.is_empty(Interner)); // quantified where clauses not yet handled
                         self.push_obligation(var_predicate.cast(Interner));
                     }
+                    self.result.type_of_rpit.insert(idx, var.clone());
                     var
                 },
                 DebruijnIndex::INNERMOST,

crates/hir-ty/src/layout.rs

@@ -225,10 +225,21 @@ pub fn layout_of_ty(db: &dyn HirDatabase, ty: &Ty, krate: CrateId) -> Result<Lay
             ptr.valid_range_mut().start = 1;
             Layout::scalar(dl, ptr)
         }
-        TyKind::Closure(_, _)
-        | TyKind::OpaqueType(_, _)
-        | TyKind::Generator(_, _)
-        | TyKind::GeneratorWitness(_, _) => return Err(LayoutError::NotImplemented),
+        TyKind::OpaqueType(opaque_ty_id, _) => {
+            let impl_trait_id = db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
+            match impl_trait_id {
+                crate::ImplTraitId::ReturnTypeImplTrait(func, idx) => {
+                    let infer = db.infer(func.into());
+                    layout_of_ty(db, &infer.type_of_rpit[idx], krate)?
+                }
+                crate::ImplTraitId::AsyncBlockTypeImplTrait(_, _) => {
+                    return Err(LayoutError::NotImplemented)
+                }
+            }
+        }
+        TyKind::Closure(_, _) | TyKind::Generator(_, _) | TyKind::GeneratorWitness(_, _) => {
+            return Err(LayoutError::NotImplemented)
+        }
         TyKind::AssociatedType(_, _)
         | TyKind::Error
         | TyKind::Alias(_)

crates/hir-ty/src/layout/tests.rs

@@ -5,7 +5,7 @@ use hir_def::{
     layout::{Layout, LayoutError},
 };
 
-use crate::{test_db::TestDB, Interner, Substitution};
+use crate::{db::HirDatabase, test_db::TestDB, Interner, Substitution};
 
 use super::layout_of_ty;
 
@@ -45,13 +45,64 @@ fn eval_goal(ra_fixture: &str, minicore: &str) -> Result<Layout, LayoutError> {
     layout_of_ty(&db, &goal_ty, module_id.krate())
 }
 
+/// A version of `eval_goal` for types that can not be expressed in ADTs, like closures and `impl Trait`
+fn eval_expr(ra_fixture: &str, minicore: &str) -> Result<Layout, LayoutError> {
+    // using unstable cargo features failed, fall back to using plain rustc
+    let mut cmd = std::process::Command::new("rustc");
+    cmd.args(["-Z", "unstable-options", "--print", "target-spec-json"]).env("RUSTC_BOOTSTRAP", "1");
+    let output = cmd.output().unwrap();
+    assert!(output.status.success(), "{}", output.status);
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    let target_data_layout =
+        stdout.split_once(r#""data-layout": ""#).unwrap().1.split_once('"').unwrap().0.to_owned();
+
+    let ra_fixture = format!(
+        "{minicore}//- /main.rs crate:test target_data_layout:{target_data_layout}\nfn main(){{let goal = {{{ra_fixture}}};}}",
+    );
+
+    let (db, file_id) = TestDB::with_single_file(&ra_fixture);
+    let module_id = db.module_for_file(file_id);
+    let def_map = module_id.def_map(&db);
+    let scope = &def_map[module_id.local_id].scope;
+    let adt_id = scope
+        .declarations()
+        .find_map(|x| match x {
+            hir_def::ModuleDefId::FunctionId(x) => {
+                let name = db.function_data(x).name.to_smol_str();
+                (name == "main").then_some(x)
+            }
+            _ => None,
+        })
+        .unwrap();
+    let hir_body = db.body(adt_id.into());
+    let pat = hir_body
+        .pats
+        .iter()
+        .find(|x| match x.1 {
+            hir_def::expr::Pat::Bind { name, .. } => name.to_smol_str() == "goal",
+            _ => false,
+        })
+        .unwrap()
+        .0;
+    let infer = db.infer(adt_id.into());
+    let goal_ty = infer.type_of_pat[pat].clone();
+    layout_of_ty(&db, &goal_ty, module_id.krate())
+}
+
 #[track_caller]
 fn check_size_and_align(ra_fixture: &str, minicore: &str, size: u64, align: u64) {
     let l = eval_goal(ra_fixture, minicore).unwrap();
     assert_eq!(l.size.bytes(), size);
     assert_eq!(l.align.abi.bytes(), align);
 }
 
+#[track_caller]
+fn check_size_and_align_expr(ra_fixture: &str, minicore: &str, size: u64, align: u64) {
+    let l = eval_expr(ra_fixture, minicore).unwrap();
+    assert_eq!(l.size.bytes(), size);
+    assert_eq!(l.align.abi.bytes(), align);
+}
+
 #[track_caller]
 fn check_fail(ra_fixture: &str, e: LayoutError) {
     let r = eval_goal(ra_fixture, "");
@@ -85,11 +136,31 @@ macro_rules! size_and_align {
     };
 }
 
+macro_rules! size_and_align_expr {
+    ($($t:tt)*) => {
+        {
+            #[allow(dead_code)]
+            {
+                let val = { $($t)* };
+                check_size_and_align_expr(
+                    stringify!($($t)*),
+                    "",
+                    ::std::mem::size_of_val(&val) as u64,
+                    ::std::mem::align_of_val(&val) as u64,
+                );
+            }
+        }
+    };
+}
+
 #[test]
 fn hello_world() {
     size_and_align! {
         struct Goal(i32);
     }
+    size_and_align_expr! {
+        2i32
+    }
 }
 
 #[test]
@@ -143,6 +214,40 @@ fn generic() {
     }
 }
 
+#[test]
+fn return_position_impl_trait() {
+    size_and_align_expr! {
+        trait T {}
+        impl T for i32 {}
+        impl T for i64 {}
+        fn foo() -> impl T { 2i64 }
+        foo()
+    }
+    size_and_align_expr! {
+        trait T {}
+        impl T for i32 {}
+        impl T for i64 {}
+        fn foo() -> (impl T, impl T, impl T) { (2i64, 5i32, 7i32) }
+        foo()
+    }
+    size_and_align_expr! {
+        struct Foo<T>(T, T, (T, T));
+        trait T {}
+        impl T for Foo<i32> {}
+        impl T for Foo<i64> {}
+
+        fn foo() -> Foo<impl T> { Foo(
+            Foo(1i64, 2, (3, 4)),
+            Foo(5, 6, (7, 8)),
+            (
+                Foo(1i64, 2, (3, 4)),
+                Foo(5, 6, (7, 8)),
+            ),
+        ) }
+        foo()
+    }
+}
+
 #[test]
 fn enums() {
     size_and_align! {

crates/hir-ty/src/lib.rs

@@ -45,6 +45,7 @@ use chalk_ir::{
 use hir_def::{expr::ExprId, type_ref::Rawness, TypeOrConstParamId};
 use hir_expand::name;
 use itertools::Either;
+use la_arena::{Arena, Idx};
 use rustc_hash::FxHashSet;
 use traits::FnTrait;
 use utils::Generics;
@@ -290,22 +291,24 @@ impl TypeFoldable<Interner> for CallableSig {
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
 pub enum ImplTraitId {
-    ReturnTypeImplTrait(hir_def::FunctionId, u16),
+    ReturnTypeImplTrait(hir_def::FunctionId, RpitId),
     AsyncBlockTypeImplTrait(hir_def::DefWithBodyId, ExprId),
 }
 
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct ReturnTypeImplTraits {
-    pub(crate) impl_traits: Vec<ReturnTypeImplTrait>,
+    pub(crate) impl_traits: Arena<ReturnTypeImplTrait>,
 }
 
 has_interner!(ReturnTypeImplTraits);
 
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub(crate) struct ReturnTypeImplTrait {
+pub struct ReturnTypeImplTrait {
     pub(crate) bounds: Binders<Vec<QuantifiedWhereClause>>,
 }
 
+pub type RpitId = Idx<ReturnTypeImplTrait>;
+
 pub fn static_lifetime() -> Lifetime {
     LifetimeData::Static.intern(Interner)
 }