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Consolidate type system const evaluation under traits::evaluate_const

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mew
This commit is contained in:
Boxy 2024-11-12 02:54:03 +00:00
parent 81eef2d362
commit bea0148ac6
31 changed files with 434 additions and 569 deletions
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136
compiler/rustc_infer/src/infer/mod.rs
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@ -25,10 +25,10 @@ use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_macros::extension;
pub use rustc_macros::{TypeFoldable, TypeVisitable};
use rustc_middle::bug;
use rustc_middle::infer::canonical::{CanonicalQueryInput, CanonicalVarValues};
use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableValue, ConstVidKey};
use rustc_middle::mir::ConstraintCategory;
use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult};
use rustc_middle::traits::select;
pub use rustc_middle::ty::IntVarValue;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
@ -40,7 +40,6 @@ use rustc_middle::ty::{
self, ConstVid, FloatVid, GenericArg, GenericArgKind, GenericArgs, GenericArgsRef,
GenericParamDefKind, InferConst, IntVid, Ty, TyCtxt, TyVid, TypingMode,
};
use rustc_middle::{bug, span_bug};
use rustc_span::Span;
use rustc_span::symbol::Symbol;
use rustc_type_ir::solve::Reveal;
@ -1279,84 +1278,6 @@ impl<'tcx> InferCtxt<'tcx> {
u
}
pub fn try_const_eval_resolve(
&self,
param_env: ty::ParamEnv<'tcx>,
unevaluated: ty::UnevaluatedConst<'tcx>,
span: Span,
) -> Result<ty::Const<'tcx>, ErrorHandled> {
match self.const_eval_resolve(param_env, unevaluated, span) {
Ok(Ok(val)) => Ok(ty::Const::new_value(
self.tcx,
val,
self.tcx.type_of(unevaluated.def).instantiate(self.tcx, unevaluated.args),
)),
Ok(Err(bad_ty)) => {
let tcx = self.tcx;
let def_id = unevaluated.def;
span_bug!(
tcx.def_span(def_id),
"unable to construct a valtree for the unevaluated constant {:?}: type {bad_ty} is not valtree-compatible",
unevaluated
);
}
Err(err) => Err(err),
}
}
/// Resolves and evaluates a constant.
///
/// The constant can be located on a trait like `<A as B>::C`, in which case the given
/// generic parameters and environment are used to resolve the constant. Alternatively if the
/// constant has generic parameters in scope the instantiations are used to evaluate the value
/// of the constant. For example in `fn foo<T>() { let _ = [0; bar::<T>()]; }` the repeat count
/// constant `bar::<T>()` requires a instantiation for `T`, if the instantiation for `T` is
/// still too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is
/// returned.
///
/// This handles inferences variables within both `param_env` and `args` by
/// performing the operation on their respective canonical forms.
#[instrument(skip(self), level = "debug")]
pub fn const_eval_resolve(
&self,
mut param_env: ty::ParamEnv<'tcx>,
unevaluated: ty::UnevaluatedConst<'tcx>,
span: Span,
) -> EvalToValTreeResult<'tcx> {
let mut args = self.resolve_vars_if_possible(unevaluated.args);
debug!(?args);
// Postpone the evaluation of constants whose args depend on inference
// variables
let tcx = self.tcx;
if args.has_non_region_infer() {
if let Some(ct) = tcx.thir_abstract_const(unevaluated.def)? {
let ct = tcx.expand_abstract_consts(ct.instantiate(tcx, args));
if let Err(e) = ct.error_reported() {
return Err(ErrorHandled::Reported(e.into(), span));
} else if ct.has_non_region_infer() || ct.has_non_region_param() {
return Err(ErrorHandled::TooGeneric(span));
} else {
args = replace_param_and_infer_args_with_placeholder(tcx, args);
}
} else {
args = GenericArgs::identity_for_item(tcx, unevaluated.def);
param_env = tcx.param_env(unevaluated.def);
}
}
let param_env_erased = tcx.erase_regions(param_env);
let args_erased = tcx.erase_regions(args);
debug!(?param_env_erased);
debug!(?args_erased);
let unevaluated = ty::UnevaluatedConst { def: unevaluated.def, args: args_erased };
// The return value is the evaluated value which doesn't contain any reference to inference
// variables, thus we don't need to instantiate back the original values.
tcx.const_eval_resolve_for_typeck(param_env_erased, unevaluated, span)
}
/// The returned function is used in a fast path. If it returns `true` the variable is
/// unchanged, `false` indicates that the status is unknown.
#[inline]
@ -1622,61 +1543,6 @@ impl RegionVariableOrigin {
}
}
/// Replaces args that reference param or infer variables with suitable
/// placeholders. This function is meant to remove these param and infer
/// args when they're not actually needed to evaluate a constant.
fn replace_param_and_infer_args_with_placeholder<'tcx>(
tcx: TyCtxt<'tcx>,
args: GenericArgsRef<'tcx>,
) -> GenericArgsRef<'tcx> {
struct ReplaceParamAndInferWithPlaceholder<'tcx> {
tcx: TyCtxt<'tcx>,
idx: u32,
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReplaceParamAndInferWithPlaceholder<'tcx> {
fn cx(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
if let ty::Infer(_) = t.kind() {
let idx = {
let idx = self.idx;
self.idx += 1;
idx
};
Ty::new_placeholder(self.tcx, ty::PlaceholderType {
universe: ty::UniverseIndex::ROOT,
bound: ty::BoundTy {
var: ty::BoundVar::from_u32(idx),
kind: ty::BoundTyKind::Anon,
},
})
} else {
t.super_fold_with(self)
}
}
fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> {
if let ty::ConstKind::Infer(_) = c.kind() {
ty::Const::new_placeholder(self.tcx, ty::PlaceholderConst {
universe: ty::UniverseIndex::ROOT,
bound: ty::BoundVar::from_u32({
let idx = self.idx;
self.idx += 1;
idx
}),
})
} else {
c.super_fold_with(self)
}
}
}
args.fold_with(&mut ReplaceParamAndInferWithPlaceholder { tcx, idx: 0 })
}
impl<'tcx> InferCtxt<'tcx> {
/// Given a [`hir::Block`], get the span of its last expression or
/// statement, peeling off any inner blocks.