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Auto merge of #125507 - compiler-errors:type-length-limit, r=lcnr

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Re-implement a type-size based limit

r? lcnr

This PR reintroduces the type length limit added in #37789, which was accidentally made practically useless by the caching changes to `Ty::walk` in #72412, which caused the `walk` function to no longer walk over identical elements.

Hitting this length limit is not fatal unless we are in codegen -- so it shouldn't affect passes like the mir inliner which creates potentially very large types (which we observed, for example, when the new trait solver compiles `itertools` in `--release` mode).

This also increases the type length limit from `1048576 == 2 ** 20` to `2 ** 24`, which covers all of the code that can be reached with craterbot-check. Individual crates can increase the length limit further if desired.

Perf regression is mild and I think we should accept it -- reinstating this limit is important for the new trait solver and to make sure we don't accidentally hit more type-size related regressions in the future.

Fixes #125460
This commit is contained in:
bors 2024-07-03 11:56:36 +00:00
commit c872a1418a
54 changed files with 360 additions and 268 deletions
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9
compiler/rustc_trait_selection/src/traits/vtable.rs
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@ -6,7 +6,7 @@ use rustc_middle::bug;
use rustc_middle::query::Providers;
use rustc_middle::ty::{self, GenericParamDefKind, Ty, TyCtxt, Upcast, VtblEntry};
use rustc_middle::ty::{GenericArgs, TypeVisitableExt};
use rustc_span::{sym, Span};
use rustc_span::{sym, Span, DUMMY_SP};
use smallvec::{smallvec, SmallVec};
use std::fmt::Debug;
@ -285,13 +285,14 @@ fn vtable_entries<'tcx>(
return VtblEntry::Vacant;
}
let instance = ty::Instance::resolve_for_vtable(
let instance = ty::Instance::expect_resolve_for_vtable(
tcx,
ty::ParamEnv::reveal_all(),
def_id,
args,
)
.expect("resolution failed during building vtable representation");
DUMMY_SP,
);
VtblEntry::Method(instance)
});