rustc_infer/infer/canonical/
instantiate.rs

1//! This module contains code to instantiate new values into a
2//! `Canonical<'tcx, T>`.
3//!
4//! For an overview of what canonicalization is and how it fits into
5//! rustc, check out the [chapter in the rustc dev guide][c].
6//!
7//! [c]: https://rust-lang.github.io/chalk/book/canonical_queries/canonicalization.html
8
9use rustc_macros::extension;
10use rustc_middle::bug;
11use rustc_middle::ty::{self, FnMutDelegate, GenericArgKind, TyCtxt, TypeFoldable};
12
13use crate::infer::canonical::{Canonical, CanonicalVarValues};
14
15/// FIXME(-Znext-solver): This or public because it is shared with the
16/// new trait solver implementation. We should deduplicate canonicalization.
17#[extension(pub trait CanonicalExt<'tcx, V>)]
18impl<'tcx, V> Canonical<'tcx, V> {
19    /// Instantiate the wrapped value, replacing each canonical value
20    /// with the value given in `var_values`.
21    fn instantiate(&self, tcx: TyCtxt<'tcx>, var_values: &CanonicalVarValues<'tcx>) -> V
22    where
23        V: TypeFoldable<TyCtxt<'tcx>>,
24    {
25        self.instantiate_projected(tcx, var_values, |value| value.clone())
26    }
27
28    /// Allows one to apply a instantiation to some subset of
29    /// `self.value`. Invoke `projection_fn` with `self.value` to get
30    /// a value V that is expressed in terms of the same canonical
31    /// variables bound in `self` (usually this extracts from subset
32    /// of `self`). Apply the instantiation `var_values` to this value
33    /// V, replacing each of the canonical variables.
34    fn instantiate_projected<T>(
35        &self,
36        tcx: TyCtxt<'tcx>,
37        var_values: &CanonicalVarValues<'tcx>,
38        projection_fn: impl FnOnce(&V) -> T,
39    ) -> T
40    where
41        T: TypeFoldable<TyCtxt<'tcx>>,
42    {
43        assert_eq!(self.variables.len(), var_values.len());
44        let value = projection_fn(&self.value);
45        instantiate_value(tcx, var_values, value)
46    }
47}
48
49/// Instantiate the values from `var_values` into `value`. `var_values`
50/// must be values for the set of canonical variables that appear in
51/// `value`.
52pub(super) fn instantiate_value<'tcx, T>(
53    tcx: TyCtxt<'tcx>,
54    var_values: &CanonicalVarValues<'tcx>,
55    value: T,
56) -> T
57where
58    T: TypeFoldable<TyCtxt<'tcx>>,
59{
60    if var_values.var_values.is_empty() {
61        value
62    } else {
63        let delegate = FnMutDelegate {
64            regions: &mut |br: ty::BoundRegion| match var_values[br.var].unpack() {
65                GenericArgKind::Lifetime(l) => l,
66                r => bug!("{:?} is a region but value is {:?}", br, r),
67            },
68            types: &mut |bound_ty: ty::BoundTy| match var_values[bound_ty.var].unpack() {
69                GenericArgKind::Type(ty) => ty,
70                r => bug!("{:?} is a type but value is {:?}", bound_ty, r),
71            },
72            consts: &mut |bound_ct: ty::BoundVar| match var_values[bound_ct].unpack() {
73                GenericArgKind::Const(ct) => ct,
74                c => bug!("{:?} is a const but value is {:?}", bound_ct, c),
75            },
76        };
77
78        tcx.replace_escaping_bound_vars_uncached(value, delegate)
79    }
80}
rustc_infer/infer/canonical/instantiate.rs

rustc_infer/infer/canonical/
instantiate.rs
