diff options
5 files changed, 136 insertions, 3 deletions
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs index 32c02033dc9..6b9952ba5d6 100644 --- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs +++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs @@ -11,7 +11,7 @@ use rustc_middle::hir::map::Map; use rustc_middle::infer::unify_key::ConstVariableOriginKind; use rustc_middle::ty::print::Print; use rustc_middle::ty::subst::{GenericArg, GenericArgKind}; -use rustc_middle::ty::{self, DefIdTree, InferConst, Ty, TyCtxt}; +use rustc_middle::ty::{self, DefIdTree, InferConst, Ty, TyCtxt, TypeFoldable, TypeFolder}; use rustc_span::symbol::kw; use rustc_span::Span; use std::borrow::Cow; @@ -629,6 +629,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { format!("the explicit type `{}`, with the type parameters specified", ty) } Some(ty) if is_named_and_not_impl_trait(ty) && ty.to_string() != arg_data.name => { + let ty = ResolvedTypeParamEraser::new(self.tcx).fold_ty(ty); + let ty = ErrTypeParamEraser(self.tcx).fold_ty(ty); let ty = ty_to_string(ty); format!( "the explicit type `{}`, where the type parameter `{}` is specified", @@ -908,3 +910,99 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { err } } + +/// Turn resolved type params into `[type error]` to signal we don't want to display them. +struct ResolvedTypeParamEraser<'tcx> { + tcx: TyCtxt<'tcx>, + level: usize, +} + +impl<'tcx> ResolvedTypeParamEraser<'tcx> { + fn new(tcx: TyCtxt<'tcx>) -> Self { + ResolvedTypeParamEraser { tcx, level: 0 } + } +} +impl<'tcx> TypeFolder<'tcx> for ResolvedTypeParamEraser<'tcx> { + fn tcx<'a>(&'a self) -> TyCtxt<'tcx> { + self.tcx + } + fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { + self.level += 1; + let t = match t.kind() { + // We'll hide this type only if all its type params are hidden as well. + ty::Adt(def, substs) => { + let generics = self.tcx().generics_of(def.did); + // Account for params with default values, like `Vec`, where we + // want to show `Vec<T>`, not `Vec<T, _>`. If we replaced that + // subst, then we'd get the incorrect output, so we passthrough. + let substs: Vec<_> = substs + .iter() + .zip(generics.params.iter()) + .map(|(subst, param)| match ¶m.kind { + ty::GenericParamDefKind::Type { has_default: true, .. } => subst, + _ => subst.super_fold_with(self), + }) + .collect(); + if self.level == 1 + || substs.iter().any(|subst| match subst.unpack() { + ty::subst::GenericArgKind::Type(t) => match t.kind() { + ty::Error(_) => false, + _ => true, + }, + // Account for `const` params here, otherwise `doesnt_infer.rs` + // shows `_` instead of `Foo<{ _: u32 }>` + ty::subst::GenericArgKind::Const(_) => true, + _ => false, + }) + { + let substs = self.tcx().intern_substs(&substs[..]); + self.tcx().mk_ty(ty::Adt(def, substs)) + } else { + self.tcx().ty_error() + } + } + ty::Ref(_, ty, _) => { + let ty = self.fold_ty(ty); + match ty.kind() { + // Avoid `&_`, these can be safely presented as `_`. + ty::Error(_) => self.tcx().ty_error(), + _ => t.super_fold_with(self), + } + } + // We could account for `()` if we wanted to replace it, but it's assured to be short. + ty::Tuple(_) + | ty::Slice(_) + | ty::RawPtr(_) + | ty::FnDef(..) + | ty::FnPtr(_) + | ty::Opaque(..) + | ty::Projection(_) + | ty::Never + | ty::Array(..) => t.super_fold_with(self), + // We don't want to hide type params that haven't been resolved yet. + // This would be the type that will be written out with the type param + // name in the output. + ty::Infer(_) => t, + // We don't want to hide the outermost type, only its type params. + _ if self.level == 1 => t.super_fold_with(self), + // Hide this type + _ => self.tcx().ty_error(), + }; + self.level -= 1; + t + } +} + +/// Replace `[type error]` with `ty::Infer(ty::Var)` to display `_`. +struct ErrTypeParamEraser<'tcx>(TyCtxt<'tcx>); +impl<'tcx> TypeFolder<'tcx> for ErrTypeParamEraser<'tcx> { + fn tcx<'a>(&'a self) -> TyCtxt<'tcx> { + self.0 + } + fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { + match t.kind() { + ty::Error(_) => self.tcx().mk_ty_var(ty::TyVid::from_u32(0)), + _ => t.super_fold_with(self), + } + } +} diff --git a/src/test/ui/const-generics/defaults/doesnt_infer.stderr b/src/test/ui/const-generics/defaults/doesnt_infer.stderr index b57975e26f2..183be1b1517 100644 --- a/src/test/ui/const-generics/defaults/doesnt_infer.stderr +++ b/src/test/ui/const-generics/defaults/doesnt_infer.stderr @@ -4,7 +4,7 @@ error[E0282]: type annotations needed for `Foo<{_: u32}>` LL | let foo = Foo::foo(); | --- ^^^^^^^^ cannot infer the value of const parameter `N` | | - | consider giving `foo` the explicit type `Foo<{_: u32}>`, where the type parameter `N` is specified + | consider giving `foo` the explicit type `Foo<{_: _}>`, where the type parameter `N` is specified error: aborting due to previous error diff --git a/src/test/ui/inference/erase-type-params-in-label.rs b/src/test/ui/inference/erase-type-params-in-label.rs new file mode 100644 index 00000000000..4a163d0b810 --- /dev/null +++ b/src/test/ui/inference/erase-type-params-in-label.rs @@ -0,0 +1,13 @@ +fn main() { + let foo = new(1, ""); //~ ERROR E0283 +} + +struct Bar<T, K, N: Default> { + t: T, + k: K, + n: N, +} + +fn new<T, K, Z: Default>(t: T, k: K) -> Bar<T, K, Z> { + Bar { t, k, n: Default::default() } +} diff --git a/src/test/ui/inference/erase-type-params-in-label.stderr b/src/test/ui/inference/erase-type-params-in-label.stderr new file mode 100644 index 00000000000..b665fade9d8 --- /dev/null +++ b/src/test/ui/inference/erase-type-params-in-label.stderr @@ -0,0 +1,22 @@ +error[E0283]: type annotations needed for `Bar<i32, &str, Z>` + --> $DIR/erase-type-params-in-label.rs:2:15 + | +LL | let foo = new(1, ""); + | --- ^^^ cannot infer type for type parameter `Z` declared on the function `new` + | | + | consider giving `foo` the explicit type `Bar<_, _, Z>`, where the type parameter `Z` is specified + | + = note: cannot satisfy `_: Default` +note: required by a bound in `new` + --> $DIR/erase-type-params-in-label.rs:11:17 + | +LL | fn new<T, K, Z: Default>(t: T, k: K) -> Bar<T, K, Z> { + | ^^^^^^^ required by this bound in `new` +help: consider specifying the type arguments in the function call + | +LL | let foo = new::<T, K, Z>(1, ""); + | +++++++++++ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0283`. diff --git a/src/test/ui/inference/issue-83606.stderr b/src/test/ui/inference/issue-83606.stderr index 65f3336b935..c66606b9c83 100644 --- a/src/test/ui/inference/issue-83606.stderr +++ b/src/test/ui/inference/issue-83606.stderr @@ -4,7 +4,7 @@ error[E0282]: type annotations needed for `[usize; _]` LL | let _ = foo("foo"); //<- Do not suggest `foo::<N>("foo");`! | - ^^^ cannot infer the value of const parameter `N` declared on the function `foo` | | - | consider giving this pattern the explicit type `[usize; _]`, where the type parameter `N` is specified + | consider giving this pattern the explicit type `[_; _]`, where the type parameter `N` is specified error: aborting due to previous error |