Auto merge of #90050 - michaelwoerister:fix-vtable-debug-name-crash-90019, r=wesleywiser

Erase late-bound regions before computing vtable debuginfo name.

Fixes #90019.

The `msvc_enum_fallback()` for computing enum type names needs to access the memory layout of niche enums in order to determine the type name. `compute_debuginfo_vtable_name()` did not properly erase regions before computing type names which made memory layout computation ICE when encountering un-erased regions.

r? `@wesleywiser`

1 files changed, 10 insertions, 0 deletions

diff --git a/src/test/codegen/debug-vtable.rs b/src/test/codegen/debug-vtable.rs
index 851d68da5ee..1c8cc61f204 100644
--- a/src/test/codegen/debug-vtable.rs
+++ b/src/test/codegen/debug-vtable.rs
@@ -18,6 +18,9 @@
 // MSVC-LABEL: !DIGlobalVariable(name: "impl$<debug_vtable::Foo, _>::vtable$"
 // CHECK: !DISubrange(count: 3
 
+// NONMSVC-LABEL: !DIGlobalVariable(name: "<debug_vtable::bar::{closure#0} as core::ops::function::FnOnce<(core::option::Option<&dyn core::ops::function::Fn<(), Output=()>>)>>::{vtable}"
+// MSVC-LABEL: !DIGlobalVariable(name: "impl$<debug_vtable::bar::closure$0, core::ops::function::FnOnce<tuple$<enum$<core::option::Option<ref$<dyn$<core::ops::function::Fn<tuple$<>,assoc$<Output,tuple$<> > > > > >, {{.*}}, {{.*}}, Some> > > >::vtable$"
+
 #![crate_type = "lib"]
 
 pub struct Foo;
@@ -45,3 +48,10 @@ pub fn foo(x: &Foo) -> (u32, (u64, i8), &dyn Send) {
     let z: &dyn SomeTraitWithGenerics<u64, i8> = x;
     (y.method1(), z.method1(), x as &dyn Send)
 }
+
+// Constructing the debuginfo name for the FnOnce vtable below initially caused an ICE on MSVC
+// because the trait type contains a late bound region that needed to be erased before the type
+// layout for the niche enum `Option<&dyn Fn()>` could be computed.
+pub fn bar() -> Box<dyn FnOnce(Option<&dyn Fn()>)> {
+    Box::new(|_x: Option<&dyn Fn()>| {})
+}