From 8841204cc66f66e0e090b4a0c876e861e4cc75f7 Mon Sep 17 00:00:00 2001
From: Charles Lew <crlf0710@gmail.com>
Date: Wed, 3 Nov 2021 23:37:50 +0800
Subject: [PATCH] Erase regions within `vtable_trait_first_method_offset`.

---
 .../rustc_trait_selection/src/traits/mod.rs   |  5 ++-
 src/test/ui/hrtb/issue-90177.rs               | 32 +++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/hrtb/issue-90177.rs

diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index 428873b8d3dda..8f247184e8808 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -748,6 +748,9 @@ fn vtable_trait_first_method_offset<'tcx>(
 ) -> usize {
     let (trait_to_be_found, trait_owning_vtable) = key;
 
+    // #90177
+    let trait_to_be_found_erased = tcx.erase_regions(trait_to_be_found);
+
     let vtable_segment_callback = {
         let mut vtable_base = 0;
 
@@ -757,7 +760,7 @@ fn vtable_trait_first_method_offset<'tcx>(
                     vtable_base += COMMON_VTABLE_ENTRIES.len();
                 }
                 VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
-                    if trait_ref == trait_to_be_found {
+                    if tcx.erase_regions(trait_ref) == trait_to_be_found_erased {
                         return ControlFlow::Break(vtable_base);
                     }
                     vtable_base += util::count_own_vtable_entries(tcx, trait_ref);
diff --git a/src/test/ui/hrtb/issue-90177.rs b/src/test/ui/hrtb/issue-90177.rs
new file mode 100644
index 0000000000000..b151a9d3ab659
--- /dev/null
+++ b/src/test/ui/hrtb/issue-90177.rs
@@ -0,0 +1,32 @@
+// check-pass
+
+trait Base<'f> {
+    type Assoc;
+
+    fn do_something(&self);
+}
+
+trait ForAnyLifetime: for<'f> Base<'f> {}
+
+impl<T> ForAnyLifetime for T where T: for<'f> Base<'f> {}
+
+trait CanBeDynamic: ForAnyLifetime + for<'f> Base<'f, Assoc = ()> {}
+
+fn foo(a: &dyn CanBeDynamic) {
+    a.do_something();
+}
+
+struct S;
+
+impl<'a> Base<'a> for S {
+    type Assoc = ();
+
+    fn do_something(&self) {}
+}
+
+impl CanBeDynamic for S {}
+
+fn main() {
+    let s = S;
+    foo(&s);
+}