diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/librustc/infer/opaque_types/mod.rs | 5 | ||||
| -rw-r--r-- | src/librustc_typeck/check/mod.rs | 101 | ||||
| -rw-r--r-- | src/test/ui/impl-trait/where-allowed-2.rs | 9 | ||||
| -rw-r--r-- | src/test/ui/impl-trait/where-allowed-2.stderr | 11 | ||||
| -rw-r--r-- | src/test/ui/impl-trait/where-allowed.rs | 5 | ||||
| -rw-r--r-- | src/test/ui/type-alias-impl-trait/fallback.rs | 22 |
6 files changed, 144 insertions, 9 deletions
diff --git a/src/librustc/infer/opaque_types/mod.rs b/src/librustc/infer/opaque_types/mod.rs index 9ed60b1f0c1..500122ce8c4 100644 --- a/src/librustc/infer/opaque_types/mod.rs +++ b/src/librustc/infer/opaque_types/mod.rs @@ -24,6 +24,10 @@ pub type OpaqueTypeMap<'tcx> = DefIdMap<OpaqueTypeDecl<'tcx>>; /// appear in the return type). #[derive(Copy, Clone, Debug)] pub struct OpaqueTypeDecl<'tcx> { + + /// The opaque type (`ty::Opaque`) for this declaration + pub opaque_type: Ty<'tcx>, + /// The substitutions that we apply to the opaque type that this /// `impl Trait` desugars to. e.g., if: /// @@ -1150,6 +1154,7 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> { self.opaque_types.insert( def_id, OpaqueTypeDecl { + opaque_type: ty, substs, definition_span, concrete_ty: ty_var, diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs index a8418c5f349..6c2f6e4fb3e 100644 --- a/src/librustc_typeck/check/mod.rs +++ b/src/librustc_typeck/check/mod.rs @@ -147,7 +147,7 @@ use crate::TypeAndSubsts; use crate::lint; use crate::util::captures::Captures; use crate::util::common::{ErrorReported, indenter}; -use crate::util::nodemap::{DefIdMap, DefIdSet, FxHashSet, HirIdMap}; +use crate::util::nodemap::{DefIdMap, DefIdSet, FxHashMap, FxHashSet, HirIdMap}; pub use self::Expectation::*; use self::autoderef::Autoderef; @@ -231,6 +231,13 @@ pub struct Inherited<'a, 'tcx> { // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions. opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>, + /// A map from inference variables created from opaque + /// type instantiations (ty::Infer) to the actual opaque + /// type (`ty::Opaque`). Used during fallback to map unconstrained + /// opaque type inference variables to their corresponding + /// opaque type. + opaque_types_vars: RefCell<FxHashMap<Ty<'tcx>, Ty<'tcx>>>, + /// Each type parameter has an implicit region bound that /// indicates it must outlive at least the function body (the user /// may specify stronger requirements). This field indicates the @@ -696,6 +703,7 @@ impl Inherited<'a, 'tcx> { deferred_cast_checks: RefCell::new(Vec::new()), deferred_generator_interiors: RefCell::new(Vec::new()), opaque_types: RefCell::new(Default::default()), + opaque_types_vars: RefCell::new(Default::default()), implicit_region_bound, body_id, } @@ -937,9 +945,46 @@ fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> { // All type checking constraints were added, try to fallback unsolved variables. fcx.select_obligations_where_possible(false, |_| {}); let mut fallback_has_occurred = false; + + // We do fallback in two passes, to try to generate + // better error messages. + // The first time, we do *not* replace opaque types. + for ty in &fcx.unsolved_variables() { + fallback_has_occurred |= fcx.fallback_if_possible(ty, false /* opaque_fallback */); + } + // We now see if we can make progress. This might + // cause us to unify inference variables for opaque types, + // since we may have unified some other type variables + // during the first phase of fallback. + // This means that we only replace inference variables with their underlying + // opaque types as a last resort. + // + // In code like this: + // + // ```rust + // type MyType = impl Copy; + // fn produce() -> MyType { true } + // fn bad_produce() -> MyType { panic!() } + // ``` + // + // we want to unify the opaque inference variable in `bad_produce` + // with the diverging fallback for `panic!` (e.g. `()` or `!`), + // This will produce a nice error message about conflicting concrete + // types for `MyType`. + // + // If we had tried to fallback the opaque inference variable to `MyType`, + // we will generate a confusing type-check error that does not explicitly + // refer to opaque types. + fcx.select_obligations_where_possible(fallback_has_occurred, |_| {}); + + // We now run fallback again, but this time we allow it to replace + // unconstrained opaque type variables, in addition to performing + // other kinds of fallback. for ty in &fcx.unsolved_variables() { - fallback_has_occurred |= fcx.fallback_if_possible(ty); + fallback_has_occurred |= fcx.fallback_if_possible(ty, true /* opaque_fallback */); } + + // See if we can make any more progress fcx.select_obligations_where_possible(fallback_has_occurred, |_| {}); // Even though coercion casts provide type hints, we check casts after fallback for @@ -2864,8 +2909,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { ); let mut opaque_types = self.opaque_types.borrow_mut(); + let mut opaque_types_vars = self.opaque_types_vars.borrow_mut(); for (ty, decl) in opaque_type_map { let _ = opaque_types.insert(ty, decl); + let _ = opaque_types_vars.insert(decl.concrete_ty, decl.opaque_type); } value @@ -3078,7 +3125,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { // Fallback becomes very dubious if we have encountered type-checking errors. // In that case, fallback to Error. // The return value indicates whether fallback has occurred. - fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool { + fn fallback_if_possible(&self, ty: Ty<'tcx>, opaque_fallback: bool) -> bool { use rustc::ty::error::UnconstrainedNumeric::Neither; use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat}; @@ -3088,7 +3135,53 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { UnconstrainedInt => self.tcx.types.i32, UnconstrainedFloat => self.tcx.types.f64, Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(), - Neither => return false, + Neither => { + // This type variable was created from the instantiation of an opaque + // type. The fact that we're attempting to perform fallback for it + // means that the function neither constrained it to a concrete + // type, nor to the opaque type itself. + // + // For example, in this code: + // + //``` + // type MyType = impl Copy; + // fn defining_use() -> MyType { true } + // fn other_use() -> MyType { defining_use() } + // ``` + // + // `defining_use` will constrain the instantiated inference + // variable to `bool`, while `other_use` will constrain + // the instantiated inference variable to `MyType`. + // + // When we process opaque types during writeback, we + // will handle cases like `other_use`, and not count + // them as defining usages + // + // However, we also need to handle cases like this: + // + // ```rust + // pub type Foo = impl Copy; + // fn produce() -> Option<Foo> { + // None + // } + // ``` + // + // In the above snippet, the inference varaible created by + // instantiating `Option<Foo>` will be completely unconstrained. + // We treat this as a non-defining use by making the inference + // variable fall back to the opaque type itself. + if opaque_fallback { + if let Some(opaque_ty) = self.opaque_types_vars.borrow().get(ty) { + debug!("fallback_if_possible: falling back opaque type var {:?} to {:?}", + ty, opaque_ty); + *opaque_ty + } else { + return false; + } + } else { + return false; + } + }, }; debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback); self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback); diff --git a/src/test/ui/impl-trait/where-allowed-2.rs b/src/test/ui/impl-trait/where-allowed-2.rs new file mode 100644 index 00000000000..f7744ef1b3e --- /dev/null +++ b/src/test/ui/impl-trait/where-allowed-2.rs @@ -0,0 +1,9 @@ +//! Ideally, these tests would go in `where-allowed.rs`, but we bail out +//! too early to display them. +use std::fmt::Debug; + +// Disallowed +fn in_adt_in_return() -> Vec<impl Debug> { panic!() } +//~^ ERROR opaque type expands to a recursive type + +fn main() {} diff --git a/src/test/ui/impl-trait/where-allowed-2.stderr b/src/test/ui/impl-trait/where-allowed-2.stderr new file mode 100644 index 00000000000..1de15014c1f --- /dev/null +++ b/src/test/ui/impl-trait/where-allowed-2.stderr @@ -0,0 +1,11 @@ +error[E0720]: opaque type expands to a recursive type + --> $DIR/where-allowed-2.rs:6:30 + | +LL | fn in_adt_in_return() -> Vec<impl Debug> { panic!() } + | ^^^^^^^^^^ expands to a recursive type + | + = note: type resolves to itself + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0720`. diff --git a/src/test/ui/impl-trait/where-allowed.rs b/src/test/ui/impl-trait/where-allowed.rs index 5ab74e02e0e..211a14ed4dd 100644 --- a/src/test/ui/impl-trait/where-allowed.rs +++ b/src/test/ui/impl-trait/where-allowed.rs @@ -12,10 +12,6 @@ fn in_return() -> impl Debug { panic!() } fn in_adt_in_parameters(_: Vec<impl Debug>) { panic!() } // Disallowed -fn in_adt_in_return() -> Vec<impl Debug> { panic!() } -//~^ ERROR type annotations needed - -// Disallowed fn in_fn_parameter_in_parameters(_: fn(impl Debug)) { panic!() } //~^ ERROR `impl Trait` not allowed outside of function and inherent method return types @@ -60,7 +56,6 @@ fn in_impl_Fn_return_in_parameters(_: &impl Fn() -> impl Debug) { panic!() } fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() } //~^ ERROR `impl Trait` not allowed outside of function and inherent method return types //~| ERROR nested `impl Trait` is not allowed -//~| ERROR type annotations needed // Disallowed fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() } diff --git a/src/test/ui/type-alias-impl-trait/fallback.rs b/src/test/ui/type-alias-impl-trait/fallback.rs new file mode 100644 index 00000000000..c59c1e3b7d0 --- /dev/null +++ b/src/test/ui/type-alias-impl-trait/fallback.rs @@ -0,0 +1,22 @@ +// Tests that we correctly handle the instantiated +// inference variable being completely unconstrained. +// +// check-pass +#![feature(type_alias_impl_trait)] + +type Foo = impl Copy; + +enum Wrapper<T> { + First(T), + Second +} + +fn _make_iter() -> Foo { + true +} + +fn _produce() -> Wrapper<Foo> { + Wrapper::Second +} + +fn main() {} |