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Mark Printer methods as unreachable where appropriate.

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This helps me understand the structure of the code a lot.

If any of these are actually reachable, we can put the old code back,
add a new test case, and we will have improved our test coverage.
This commit is contained in:
Nicholas Nethercote 2025-08-01 08:10:16 +10:00
parent da19b9d24c
commit df524163be
4 changed files with 17 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

2
compiler/rustc_const_eval/src/util/type_name.rs
View file

@ -18,7 +18,7 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
}
fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
Ok(())
unreachable!(); // because `<Self As PrettyPrinter>::should_print_region` returns false
}
fn print_type(&mut self, ty: Ty<'tcx>) -> Result<(), PrintError> {

16
compiler/rustc_lint/src/context.rs
View file

@ -756,22 +756,22 @@ impl<'tcx> LateContext<'tcx> {
}
fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
Ok(())
unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
}
fn print_type(&mut self, _ty: Ty<'tcx>) -> Result<(), PrintError> {
Ok(())
unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
}
fn print_dyn_existential(
&mut self,
_predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
) -> Result<(), PrintError> {
Ok(())
unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
}
fn print_const(&mut self, _ct: ty::Const<'tcx>) -> Result<(), PrintError> {
Ok(())
unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
}
fn path_crate(&mut self, cnum: CrateNum) -> Result<(), PrintError> {
@ -784,10 +784,10 @@ impl<'tcx> LateContext<'tcx> {
self_ty: Ty<'tcx>,
trait_ref: Option<ty::TraitRef<'tcx>>,
) -> Result<(), PrintError> {
if trait_ref.is_none() {
if let ty::Adt(def, args) = self_ty.kind() {
return self.print_def_path(def.did(), args);
}
if trait_ref.is_none()
&& let ty::Adt(def, args) = self_ty.kind()
{
return self.print_def_path(def.did(), args);
}
// This shouldn't ever be needed, but just in case:

2
compiler/rustc_symbol_mangling/src/legacy.rs
View file

@ -236,7 +236,7 @@ impl<'tcx> Printer<'tcx> for SymbolPrinter<'tcx> {
}
fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
Ok(())
unreachable!(); // because `<Self As PrettyPrinter>::should_print_region` returns false
}
fn print_type(&mut self, ty: Ty<'tcx>) -> Result<(), PrintError> {

11
compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
View file

@ -235,28 +235,29 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
}
fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
Err(fmt::Error)
unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
}
fn print_type(&mut self, _ty: Ty<'tcx>) -> Result<(), PrintError> {
Err(fmt::Error)
unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
}
fn print_dyn_existential(
&mut self,
_predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
) -> Result<(), PrintError> {
Err(fmt::Error)
unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
}
fn print_const(&mut self, _ct: ty::Const<'tcx>) -> Result<(), PrintError> {
Err(fmt::Error)
unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
}
fn path_crate(&mut self, cnum: CrateNum) -> Result<(), PrintError> {
self.segments = vec![self.tcx.crate_name(cnum)];
Ok(())
}
fn path_qualified(
&mut self,
_self_ty: Ty<'tcx>,
@ -274,6 +275,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
) -> Result<(), PrintError> {
Err(fmt::Error)
}
fn path_append(
&mut self,
print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
@ -283,6 +285,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
self.segments.push(disambiguated_data.as_sym(true));
Ok(())
}
fn path_generic_args(
&mut self,
print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,