Auto merge of #112687 - compiler-errors:simplify-impl-source, r=lcnr

Simplify `ImplSource` candidates a bit

Reduce the number of impl source candidates, which will hopefully make our life easier when trying to adapt things like `SelectionContext::select` and `codegen_select_candidate` for the new solver.

r? `@lcnr` but feel free to reassign

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -781,8 +781,17 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                             );
                             return;
                         }
-                        Ok(Some(ImplSource::Closure(data))) => {
-                            if !tcx.is_const_fn_raw(data.closure_def_id) {
+                        // Closure: Fn{Once|Mut}
+                        Ok(Some(ImplSource::Builtin(_)))
+                            if poly_trait_pred.self_ty().skip_binder().is_closure()
+                                && tcx.fn_trait_kind_from_def_id(trait_id).is_some() =>
+                        {
+                            let ty::Closure(closure_def_id, substs) =
+                                *poly_trait_pred.self_ty().no_bound_vars().unwrap().kind()
+                            else {
+                                unreachable!()
+                            };
+                            if !tcx.is_const_fn_raw(closure_def_id) {
                                 self.check_op(ops::FnCallNonConst {
                                     caller,
                                     callee,

compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs

@@ -172,7 +172,7 @@ impl Qualif for NeedsNonConstDrop {
 
         if !matches!(
             impl_src,
-            ImplSource::ConstDestruct(_) | ImplSource::Param(_, ty::BoundConstness::ConstIfConst)
+            ImplSource::Builtin(_) | ImplSource::Param(_, ty::BoundConstness::ConstIfConst)
         ) {
             // If our const destruct candidate is not ConstDestruct or implied by the param env,
             // then it's bad

compiler/rustc_middle/src/traits/mod.rs

@@ -646,97 +646,53 @@ pub enum ImplSource<'tcx, N> {
     /// ImplSource identifying a particular impl.
     UserDefined(ImplSourceUserDefinedData<'tcx, N>),
 
-    /// ImplSource for auto trait implementations.
-    /// This carries the information and nested obligations with regards
-    /// to an auto implementation for a trait `Trait`. The nested obligations
-    /// ensure the trait implementation holds for all the constituent types.
-    AutoImpl(ImplSourceAutoImplData<N>),
-
     /// Successful resolution to an obligation provided by the caller
     /// for some type parameter. The `Vec<N>` represents the
     /// obligations incurred from normalizing the where-clause (if
     /// any).
     Param(Vec<N>, ty::BoundConstness),
 
     /// Virtual calls through an object.
-    Object(ImplSourceObjectData<'tcx, N>),
+    Object(ImplSourceObjectData<N>),
 
     /// Successful resolution for a builtin trait.
-    Builtin(ImplSourceBuiltinData<N>),
+    Builtin(Vec<N>),
 
     /// ImplSource for trait upcasting coercion
-    TraitUpcasting(ImplSourceTraitUpcastingData<'tcx, N>),
-
-    /// ImplSource automatically generated for a closure. The `DefId` is the ID
-    /// of the closure expression. This is an `ImplSource::UserDefined` in spirit, but the
-    /// impl is generated by the compiler and does not appear in the source.
-    Closure(ImplSourceClosureData<'tcx, N>),
-
-    /// Same as above, but for a function pointer type with the given signature.
-    FnPointer(ImplSourceFnPointerData<'tcx, N>),
-
-    /// ImplSource automatically generated for a generator.
-    Generator(ImplSourceGeneratorData<'tcx, N>),
-
-    /// ImplSource automatically generated for a generator backing an async future.
-    Future(ImplSourceFutureData<'tcx, N>),
+    TraitUpcasting(ImplSourceTraitUpcastingData<N>),
 
     /// ImplSource for a trait alias.
     TraitAlias(ImplSourceTraitAliasData<'tcx, N>),
-
-    /// ImplSource for a `const Drop` implementation.
-    ConstDestruct(ImplSourceConstDestructData<N>),
 }
 
 impl<'tcx, N> ImplSource<'tcx, N> {
     pub fn nested_obligations(self) -> Vec<N> {
         match self {
             ImplSource::UserDefined(i) => i.nested,
-            ImplSource::Param(n, _) => n,
-            ImplSource::Builtin(i) => i.nested,
-            ImplSource::AutoImpl(d) => d.nested,
-            ImplSource::Closure(c) => c.nested,
-            ImplSource::Generator(c) => c.nested,
-            ImplSource::Future(c) => c.nested,
+            ImplSource::Param(n, _) | ImplSource::Builtin(n) => n,
             ImplSource::Object(d) => d.nested,
-            ImplSource::FnPointer(d) => d.nested,
             ImplSource::TraitAlias(d) => d.nested,
             ImplSource::TraitUpcasting(d) => d.nested,
-            ImplSource::ConstDestruct(i) => i.nested,
         }
     }
 
     pub fn borrow_nested_obligations(&self) -> &[N] {
         match self {
             ImplSource::UserDefined(i) => &i.nested,
-            ImplSource::Param(n, _) => n,
-            ImplSource::Builtin(i) => &i.nested,
-            ImplSource::AutoImpl(d) => &d.nested,
-            ImplSource::Closure(c) => &c.nested,
-            ImplSource::Generator(c) => &c.nested,
-            ImplSource::Future(c) => &c.nested,
+            ImplSource::Param(n, _) | ImplSource::Builtin(n) => &n,
             ImplSource::Object(d) => &d.nested,
-            ImplSource::FnPointer(d) => &d.nested,
             ImplSource::TraitAlias(d) => &d.nested,
             ImplSource::TraitUpcasting(d) => &d.nested,
-            ImplSource::ConstDestruct(i) => &i.nested,
         }
     }
 
     pub fn borrow_nested_obligations_mut(&mut self) -> &mut [N] {
         match self {
             ImplSource::UserDefined(i) => &mut i.nested,
-            ImplSource::Param(n, _) => n,
-            ImplSource::Builtin(i) => &mut i.nested,
-            ImplSource::AutoImpl(d) => &mut d.nested,
-            ImplSource::Closure(c) => &mut c.nested,
-            ImplSource::Generator(c) => &mut c.nested,
-            ImplSource::Future(c) => &mut c.nested,
+            ImplSource::Param(n, _) | ImplSource::Builtin(n) => n,
             ImplSource::Object(d) => &mut d.nested,
-            ImplSource::FnPointer(d) => &mut d.nested,
             ImplSource::TraitAlias(d) => &mut d.nested,
             ImplSource::TraitUpcasting(d) => &mut d.nested,
-            ImplSource::ConstDestruct(i) => &mut i.nested,
         }
     }
 
@@ -751,54 +707,23 @@ impl<'tcx, N> ImplSource<'tcx, N> {
                 nested: i.nested.into_iter().map(f).collect(),
             }),
             ImplSource::Param(n, ct) => ImplSource::Param(n.into_iter().map(f).collect(), ct),
-            ImplSource::Builtin(i) => ImplSource::Builtin(ImplSourceBuiltinData {
-                nested: i.nested.into_iter().map(f).collect(),
-            }),
+            ImplSource::Builtin(n) => ImplSource::Builtin(n.into_iter().map(f).collect()),
             ImplSource::Object(o) => ImplSource::Object(ImplSourceObjectData {
-                upcast_trait_ref: o.upcast_trait_ref,
+                upcast_trait_def_id: o.upcast_trait_def_id,
                 vtable_base: o.vtable_base,
                 nested: o.nested.into_iter().map(f).collect(),
             }),
-            ImplSource::AutoImpl(d) => ImplSource::AutoImpl(ImplSourceAutoImplData {
-                trait_def_id: d.trait_def_id,
-                nested: d.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::Closure(c) => ImplSource::Closure(ImplSourceClosureData {
-                closure_def_id: c.closure_def_id,
-                substs: c.substs,
-                nested: c.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::Generator(c) => ImplSource::Generator(ImplSourceGeneratorData {
-                generator_def_id: c.generator_def_id,
-                substs: c.substs,
-                nested: c.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::Future(c) => ImplSource::Future(ImplSourceFutureData {
-                generator_def_id: c.generator_def_id,
-                substs: c.substs,
-                nested: c.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::FnPointer(p) => ImplSource::FnPointer(ImplSourceFnPointerData {
-                fn_ty: p.fn_ty,
-                nested: p.nested.into_iter().map(f).collect(),
-            }),
             ImplSource::TraitAlias(d) => ImplSource::TraitAlias(ImplSourceTraitAliasData {
                 alias_def_id: d.alias_def_id,
                 substs: d.substs,
                 nested: d.nested.into_iter().map(f).collect(),
             }),
             ImplSource::TraitUpcasting(d) => {
                 ImplSource::TraitUpcasting(ImplSourceTraitUpcastingData {
-                    upcast_trait_ref: d.upcast_trait_ref,
                     vtable_vptr_slot: d.vtable_vptr_slot,
                     nested: d.nested.into_iter().map(f).collect(),
                 })
             }
-            ImplSource::ConstDestruct(i) => {
-                ImplSource::ConstDestruct(ImplSourceConstDestructData {
-                    nested: i.nested.into_iter().map(f).collect(),
-                })
-            }
         }
     }
 }
@@ -823,47 +748,7 @@ pub struct ImplSourceUserDefinedData<'tcx, N> {
 
 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
 #[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceGeneratorData<'tcx, N> {
-    pub generator_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    /// Nested obligations. This can be non-empty if the generator
-    /// signature contains associated types.
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceFutureData<'tcx, N> {
-    pub generator_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    /// Nested obligations. This can be non-empty if the generator
-    /// signature contains associated types.
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceClosureData<'tcx, N> {
-    pub closure_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    /// Nested obligations. This can be non-empty if the closure
-    /// signature contains associated types.
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceAutoImplData<N> {
-    pub trait_def_id: DefId,
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceTraitUpcastingData<'tcx, N> {
-    /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
-    pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
-
+pub struct ImplSourceTraitUpcastingData<N> {
     /// The vtable is formed by concatenating together the method lists of
     /// the base object trait and all supertraits, pointers to supertrait vtable will
     /// be provided when necessary; this is the position of `upcast_trait_ref`'s vtable
@@ -873,17 +758,11 @@ pub struct ImplSourceTraitUpcastingData<'tcx, N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceBuiltinData<N> {
-    pub nested: Vec<N>,
-}
-
 #[derive(PartialEq, Eq, Clone, TyEncodable, TyDecodable, HashStable, Lift)]
 #[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceObjectData<'tcx, N> {
+pub struct ImplSourceObjectData<N> {
     /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
-    pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
+    pub upcast_trait_def_id: DefId,
 
     /// The vtable is formed by concatenating together the method lists of
     /// the base object trait and all supertraits, pointers to supertrait vtable will
@@ -894,19 +773,6 @@ pub struct ImplSourceObjectData<'tcx, N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceFnPointerData<'tcx, N> {
-    pub fn_ty: Ty<'tcx>,
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceConstDestructData<N> {
-    pub nested: Vec<N>,
-}
-
 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceTraitAliasData<'tcx, N> {