Skip to content

Clarify why InhabitedPredicate::instantiate_opt exists #137820

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Mar 7, 2025
Merged

Clarify why InhabitedPredicate::instantiate_opt exists #137820

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
da3e736
Clarify why InhabitedPredicate::instantiate_opt exists
meithecatte Feb 28, 2025
a3d63fb
InhabitedPredicate: avoid using a wildcard branch
meithecatte Mar 3, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 9 additions & 1 deletion compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -236,6 +236,11 @@ impl<'tcx> InhabitedPredicate<'tcx> {
self.instantiate_opt(tcx, args).unwrap_or(self)
}

/// Same as [`Self::instantiate`], but if there is no generics to
/// instantiate, returns `None`. This is useful because it lets us avoid
/// allocating a recursive copy of everything when the result is unchanged.
///
/// Only used to implement `instantiate` itself.
fn instantiate_opt(self, tcx: TyCtxt<'tcx>, args: ty::GenericArgsRef<'tcx>) -> Option<Self> {
match self {
Self::ConstIsZero(c) => {
Expand All @@ -260,7 +265,10 @@ impl<'tcx> InhabitedPredicate<'tcx> {
Some(InhabitedPredicate::True) => Some(InhabitedPredicate::True),
Some(a) => Some(a.or(tcx, b.instantiate_opt(tcx, args).unwrap_or(b))),
},
_ => None,
Self::True | Self::False | Self::NotInModule(_) => None,
Self::OpaqueType(_) => {
bug!("unexpected OpaqueType in InhabitedPredicate");
}
}
}
}
Expand Down
Loading