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Make const_eval_select a real intrinsic

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This commit is contained in:
Deadbeef 2022-08-23 00:07:26 +00:00
parent 8521a8c92d
commit 075084f772
27 changed files with 432 additions and 287 deletions
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33
compiler/rustc_typeck/src/check/fn_ctxt/checks.rs
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@ -31,7 +31,7 @@ use rustc_middle::ty::visit::TypeVisitable;
use rustc_middle::ty::{self, DefIdTree, IsSuggestable, Ty, TypeSuperVisitable, TypeVisitor};
use rustc_session::Session;
use rustc_span::symbol::Ident;
use rustc_span::{self, Span};
use rustc_span::{self, sym, Span};
use rustc_trait_selection::traits::{self, ObligationCauseCode, SelectionContext};
use std::iter;
@ -224,6 +224,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let minimum_input_count = expected_input_tys.len();
let provided_arg_count = provided_args.len();
let is_const_eval_select = matches!(fn_def_id, Some(def_id) if
self.tcx.def_kind(def_id) == hir::def::DefKind::Fn
&& self.tcx.is_intrinsic(def_id)
&& self.tcx.item_name(def_id) == sym::const_eval_select);
// We introduce a helper function to demand that a given argument satisfy a given input
// This is more complicated than just checking type equality, as arguments could be coerced
// This version writes those types back so further type checking uses the narrowed types
@ -259,6 +264,32 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
return Compatibility::Incompatible(coerce_error);
}
// Check that second and third argument of `const_eval_select` must be `FnDef`, and additionally that
// the second argument must be `const fn`. The first argument must be a tuple, but this is already expressed
// in the function signature (`F: FnOnce<ARG>`), so I did not bother to add another check here.
//
// This check is here because there is currently no way to express a trait bound for `FnDef` types only.
if is_const_eval_select && (1..=2).contains(&idx) {
if let ty::FnDef(def_id, _) = checked_ty.kind() {
if idx == 1 && !self.tcx.is_const_fn_raw(*def_id) {
self.tcx
.sess
.struct_span_err(provided_arg.span, "this argument must be a `const fn`")
.help("consult the documentation on `const_eval_select` for more information")
.emit();
}
} else {
self.tcx
.sess
.struct_span_err(provided_arg.span, "this argument must be a function item")
.note(format!("expected a function item, found {checked_ty}"))
.help(
"consult the documentation on `const_eval_select` for more information",
)
.emit();
}
}
// 3. Check if the formal type is a supertype of the checked one
// and register any such obligations for future type checks
let supertype_error = self