Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 429 insertions, 0 deletions

diff --git a/compiler/rustc_infer/src/infer/at.rs b/compiler/rustc_infer/src/infer/at.rs
new file mode 100644
index 000000000..130214a65
--- /dev/null
+++ b/compiler/rustc_infer/src/infer/at.rs
@@ -0,0 +1,429 @@
+//! A nice interface for working with the infcx. The basic idea is to
+//! do `infcx.at(cause, param_env)`, which sets the "cause" of the
+//! operation as well as the surrounding parameter environment. Then
+//! you can do something like `.sub(a, b)` or `.eq(a, b)` to create a
+//! subtype or equality relationship respectively. The first argument
+//! is always the "expected" output from the POV of diagnostics.
+//!
+//! Examples:
+//! ```ignore (fragment)
+//!     infcx.at(cause, param_env).sub(a, b)
+//!     // requires that `a <: b`, with `a` considered the "expected" type
+//!
+//!     infcx.at(cause, param_env).sup(a, b)
+//!     // requires that `b <: a`, with `a` considered the "expected" type
+//!
+//!     infcx.at(cause, param_env).eq(a, b)
+//!     // requires that `a == b`, with `a` considered the "expected" type
+//! ```
+//! For finer-grained control, you can also do use `trace`:
+//! ```ignore (fragment)
+//!     infcx.at(...).trace(a, b).sub(&c, &d)
+//! ```
+//! This will set `a` and `b` as the "root" values for
+//! error-reporting, but actually operate on `c` and `d`. This is
+//! sometimes useful when the types of `c` and `d` are not traceable
+//! things. (That system should probably be refactored.)
+
+use super::*;
+
+use rustc_middle::ty::relate::{Relate, TypeRelation};
+use rustc_middle::ty::{Const, ImplSubject};
+
+pub struct At<'a, 'tcx> {
+    pub infcx: &'a InferCtxt<'a, 'tcx>,
+    pub cause: &'a ObligationCause<'tcx>,
+    pub param_env: ty::ParamEnv<'tcx>,
+    /// Whether we should define opaque types
+    /// or just treat them opaquely.
+    /// Currently only used to prevent predicate
+    /// matching from matching anything against opaque
+    /// types.
+    pub define_opaque_types: bool,
+}
+
+pub struct Trace<'a, 'tcx> {
+    at: At<'a, 'tcx>,
+    a_is_expected: bool,
+    trace: TypeTrace<'tcx>,
+}
+
+impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
+    #[inline]
+    pub fn at(
+        &'a self,
+        cause: &'a ObligationCause<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+    ) -> At<'a, 'tcx> {
+        At { infcx: self, cause, param_env, define_opaque_types: true }
+    }
+
+    /// Forks the inference context, creating a new inference context with the same inference
+    /// variables in the same state. This can be used to "branch off" many tests from the same
+    /// common state. Used in coherence.
+    pub fn fork(&self) -> Self {
+        Self {
+            tcx: self.tcx,
+            defining_use_anchor: self.defining_use_anchor,
+            considering_regions: self.considering_regions,
+            in_progress_typeck_results: self.in_progress_typeck_results,
+            inner: self.inner.clone(),
+            skip_leak_check: self.skip_leak_check.clone(),
+            lexical_region_resolutions: self.lexical_region_resolutions.clone(),
+            selection_cache: self.selection_cache.clone(),
+            evaluation_cache: self.evaluation_cache.clone(),
+            reported_trait_errors: self.reported_trait_errors.clone(),
+            reported_closure_mismatch: self.reported_closure_mismatch.clone(),
+            tainted_by_errors_flag: self.tainted_by_errors_flag.clone(),
+            err_count_on_creation: self.err_count_on_creation,
+            in_snapshot: self.in_snapshot.clone(),
+            universe: self.universe.clone(),
+        }
+    }
+}
+
+pub trait ToTrace<'tcx>: Relate<'tcx> + Copy {
+    fn to_trace(
+        tcx: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx>;
+}
+
+impl<'a, 'tcx> At<'a, 'tcx> {
+    pub fn define_opaque_types(self, define_opaque_types: bool) -> Self {
+        Self { define_opaque_types, ..self }
+    }
+
+    /// Hacky routine for equating two impl headers in coherence.
+    pub fn eq_impl_headers(
+        self,
+        expected: &ty::ImplHeader<'tcx>,
+        actual: &ty::ImplHeader<'tcx>,
+    ) -> InferResult<'tcx, ()> {
+        debug!("eq_impl_header({:?} = {:?})", expected, actual);
+        match (expected.trait_ref, actual.trait_ref) {
+            (Some(a_ref), Some(b_ref)) => self.eq(a_ref, b_ref),
+            (None, None) => self.eq(expected.self_ty, actual.self_ty),
+            _ => bug!("mk_eq_impl_headers given mismatched impl kinds"),
+        }
+    }
+
+    /// Makes `a <: b`, where `a` may or may not be expected.
+    ///
+    /// See [`At::trace_exp`] and [`Trace::sub`] for a version of
+    /// this method that only requires `T: Relate<'tcx>`
+    pub fn sub_exp<T>(self, a_is_expected: bool, a: T, b: T) -> InferResult<'tcx, ()>
+    where
+        T: ToTrace<'tcx>,
+    {
+        self.trace_exp(a_is_expected, a, b).sub(a, b)
+    }
+
+    /// Makes `actual <: expected`. For example, if type-checking a
+    /// call like `foo(x)`, where `foo: fn(i32)`, you might have
+    /// `sup(i32, x)`, since the "expected" type is the type that
+    /// appears in the signature.
+    ///
+    /// See [`At::trace`] and [`Trace::sub`] for a version of
+    /// this method that only requires `T: Relate<'tcx>`
+    pub fn sup<T>(self, expected: T, actual: T) -> InferResult<'tcx, ()>
+    where
+        T: ToTrace<'tcx>,
+    {
+        self.sub_exp(false, actual, expected)
+    }
+
+    /// Makes `expected <: actual`.
+    ///
+    /// See [`At::trace`] and [`Trace::sub`] for a version of
+    /// this method that only requires `T: Relate<'tcx>`
+    pub fn sub<T>(self, expected: T, actual: T) -> InferResult<'tcx, ()>
+    where
+        T: ToTrace<'tcx>,
+    {
+        self.sub_exp(true, expected, actual)
+    }
+
+    /// Makes `expected <: actual`.
+    ///
+    /// See [`At::trace_exp`] and [`Trace::eq`] for a version of
+    /// this method that only requires `T: Relate<'tcx>`
+    pub fn eq_exp<T>(self, a_is_expected: bool, a: T, b: T) -> InferResult<'tcx, ()>
+    where
+        T: ToTrace<'tcx>,
+    {
+        self.trace_exp(a_is_expected, a, b).eq(a, b)
+    }
+
+    /// Makes `expected <: actual`.
+    ///
+    /// See [`At::trace`] and [`Trace::eq`] for a version of
+    /// this method that only requires `T: Relate<'tcx>`
+    pub fn eq<T>(self, expected: T, actual: T) -> InferResult<'tcx, ()>
+    where
+        T: ToTrace<'tcx>,
+    {
+        self.trace(expected, actual).eq(expected, actual)
+    }
+
+    pub fn relate<T>(self, expected: T, variance: ty::Variance, actual: T) -> InferResult<'tcx, ()>
+    where
+        T: ToTrace<'tcx>,
+    {
+        match variance {
+            ty::Variance::Covariant => self.sub(expected, actual),
+            ty::Variance::Invariant => self.eq(expected, actual),
+            ty::Variance::Contravariant => self.sup(expected, actual),
+
+            // We could make this make sense but it's not readily
+            // exposed and I don't feel like dealing with it. Note
+            // that bivariance in general does a bit more than just
+            // *nothing*, it checks that the types are the same
+            // "modulo variance" basically.
+            ty::Variance::Bivariant => panic!("Bivariant given to `relate()`"),
+        }
+    }
+
+    /// Computes the least-upper-bound, or mutual supertype, of two
+    /// values. The order of the arguments doesn't matter, but since
+    /// this can result in an error (e.g., if asked to compute LUB of
+    /// u32 and i32), it is meaningful to call one of them the
+    /// "expected type".
+    ///
+    /// See [`At::trace`] and [`Trace::lub`] for a version of
+    /// this method that only requires `T: Relate<'tcx>`
+    pub fn lub<T>(self, expected: T, actual: T) -> InferResult<'tcx, T>
+    where
+        T: ToTrace<'tcx>,
+    {
+        self.trace(expected, actual).lub(expected, actual)
+    }
+
+    /// Computes the greatest-lower-bound, or mutual subtype, of two
+    /// values. As with `lub` order doesn't matter, except for error
+    /// cases.
+    ///
+    /// See [`At::trace`] and [`Trace::glb`] for a version of
+    /// this method that only requires `T: Relate<'tcx>`
+    pub fn glb<T>(self, expected: T, actual: T) -> InferResult<'tcx, T>
+    where
+        T: ToTrace<'tcx>,
+    {
+        self.trace(expected, actual).glb(expected, actual)
+    }
+
+    /// Sets the "trace" values that will be used for
+    /// error-reporting, but doesn't actually perform any operation
+    /// yet (this is useful when you want to set the trace using
+    /// distinct values from those you wish to operate upon).
+    pub fn trace<T>(self, expected: T, actual: T) -> Trace<'a, 'tcx>
+    where
+        T: ToTrace<'tcx>,
+    {
+        self.trace_exp(true, expected, actual)
+    }
+
+    /// Like `trace`, but the expected value is determined by the
+    /// boolean argument (if true, then the first argument `a` is the
+    /// "expected" value).
+    pub fn trace_exp<T>(self, a_is_expected: bool, a: T, b: T) -> Trace<'a, 'tcx>
+    where
+        T: ToTrace<'tcx>,
+    {
+        let trace = ToTrace::to_trace(self.infcx.tcx, self.cause, a_is_expected, a, b);
+        Trace { at: self, trace, a_is_expected }
+    }
+}
+
+impl<'a, 'tcx> Trace<'a, 'tcx> {
+    /// Makes `a <: b` where `a` may or may not be expected (if
+    /// `a_is_expected` is true, then `a` is expected).
+    #[instrument(skip(self), level = "debug")]
+    pub fn sub<T>(self, a: T, b: T) -> InferResult<'tcx, ()>
+    where
+        T: Relate<'tcx>,
+    {
+        let Trace { at, trace, a_is_expected } = self;
+        at.infcx.commit_if_ok(|_| {
+            let mut fields = at.infcx.combine_fields(trace, at.param_env, at.define_opaque_types);
+            fields
+                .sub(a_is_expected)
+                .relate(a, b)
+                .map(move |_| InferOk { value: (), obligations: fields.obligations })
+        })
+    }
+
+    /// Makes `a == b`; the expectation is set by the call to
+    /// `trace()`.
+    #[instrument(skip(self), level = "debug")]
+    pub fn eq<T>(self, a: T, b: T) -> InferResult<'tcx, ()>
+    where
+        T: Relate<'tcx>,
+    {
+        let Trace { at, trace, a_is_expected } = self;
+        at.infcx.commit_if_ok(|_| {
+            let mut fields = at.infcx.combine_fields(trace, at.param_env, at.define_opaque_types);
+            fields
+                .equate(a_is_expected)
+                .relate(a, b)
+                .map(move |_| InferOk { value: (), obligations: fields.obligations })
+        })
+    }
+
+    #[instrument(skip(self), level = "debug")]
+    pub fn lub<T>(self, a: T, b: T) -> InferResult<'tcx, T>
+    where
+        T: Relate<'tcx>,
+    {
+        let Trace { at, trace, a_is_expected } = self;
+        at.infcx.commit_if_ok(|_| {
+            let mut fields = at.infcx.combine_fields(trace, at.param_env, at.define_opaque_types);
+            fields
+                .lub(a_is_expected)
+                .relate(a, b)
+                .map(move |t| InferOk { value: t, obligations: fields.obligations })
+        })
+    }
+
+    #[instrument(skip(self), level = "debug")]
+    pub fn glb<T>(self, a: T, b: T) -> InferResult<'tcx, T>
+    where
+        T: Relate<'tcx>,
+    {
+        let Trace { at, trace, a_is_expected } = self;
+        at.infcx.commit_if_ok(|_| {
+            let mut fields = at.infcx.combine_fields(trace, at.param_env, at.define_opaque_types);
+            fields
+                .glb(a_is_expected)
+                .relate(a, b)
+                .map(move |t| InferOk { value: t, obligations: fields.obligations })
+        })
+    }
+}
+
+impl<'tcx> ToTrace<'tcx> for ImplSubject<'tcx> {
+    fn to_trace(
+        tcx: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx> {
+        match (a, b) {
+            (ImplSubject::Trait(trait_ref_a), ImplSubject::Trait(trait_ref_b)) => {
+                ToTrace::to_trace(tcx, cause, a_is_expected, trait_ref_a, trait_ref_b)
+            }
+            (ImplSubject::Inherent(ty_a), ImplSubject::Inherent(ty_b)) => {
+                ToTrace::to_trace(tcx, cause, a_is_expected, ty_a, ty_b)
+            }
+            (ImplSubject::Trait(_), ImplSubject::Inherent(_))
+            | (ImplSubject::Inherent(_), ImplSubject::Trait(_)) => {
+                bug!("can not trace TraitRef and Ty");
+            }
+        }
+    }
+}
+
+impl<'tcx> ToTrace<'tcx> for Ty<'tcx> {
+    fn to_trace(
+        _: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx> {
+        TypeTrace {
+            cause: cause.clone(),
+            values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
+        }
+    }
+}
+
+impl<'tcx> ToTrace<'tcx> for ty::Region<'tcx> {
+    fn to_trace(
+        _: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx> {
+        TypeTrace { cause: cause.clone(), values: Regions(ExpectedFound::new(a_is_expected, a, b)) }
+    }
+}
+
+impl<'tcx> ToTrace<'tcx> for Const<'tcx> {
+    fn to_trace(
+        _: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx> {
+        TypeTrace {
+            cause: cause.clone(),
+            values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
+        }
+    }
+}
+
+impl<'tcx> ToTrace<'tcx> for ty::Term<'tcx> {
+    fn to_trace(
+        _: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx> {
+        TypeTrace { cause: cause.clone(), values: Terms(ExpectedFound::new(a_is_expected, a, b)) }
+    }
+}
+
+impl<'tcx> ToTrace<'tcx> for ty::TraitRef<'tcx> {
+    fn to_trace(
+        _: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx> {
+        TypeTrace {
+            cause: cause.clone(),
+            values: TraitRefs(ExpectedFound::new(a_is_expected, a, b)),
+        }
+    }
+}
+
+impl<'tcx> ToTrace<'tcx> for ty::PolyTraitRef<'tcx> {
+    fn to_trace(
+        _: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx> {
+        TypeTrace {
+            cause: cause.clone(),
+            values: PolyTraitRefs(ExpectedFound::new(a_is_expected, a, b)),
+        }
+    }
+}
+
+impl<'tcx> ToTrace<'tcx> for ty::ProjectionTy<'tcx> {
+    fn to_trace(
+        tcx: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx> {
+        let a_ty = tcx.mk_projection(a.item_def_id, a.substs);
+        let b_ty = tcx.mk_projection(b.item_def_id, b.substs);
+        TypeTrace {
+            cause: cause.clone(),
+            values: Terms(ExpectedFound::new(a_is_expected, a_ty.into(), b_ty.into())),
+        }
+    }
+}