From 2c23c7f0cd7a665bbd7b173ebfc26cae223304e3 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Tue, 31 Jan 2023 20:43:18 +0000
Subject: [PATCH] Erase regions before uninhabited check

---
 compiler/rustc_borrowck/src/type_check/mod.rs |  5 ++++-
 tests/ui/uninhabited/issue-107505.rs          | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/uninhabited/issue-107505.rs

diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 06087b0c579d8..0a78bc0030be4 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -1484,7 +1484,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
             }
             None => {
-                if !sig.output().is_privately_uninhabited(self.tcx(), self.param_env) {
+                // The signature in this call can reference region variables,
+                // so erase them before calling a query.
+                let output_ty = self.tcx().erase_regions(sig.output());
+                if !output_ty.is_privately_uninhabited(self.tcx(), self.param_env) {
                     span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
                 }
             }
diff --git a/tests/ui/uninhabited/issue-107505.rs b/tests/ui/uninhabited/issue-107505.rs
new file mode 100644
index 0000000000000..61598541ddf0d
--- /dev/null
+++ b/tests/ui/uninhabited/issue-107505.rs
@@ -0,0 +1,18 @@
+// compile-flags: --crate-type=lib
+// check-pass
+
+// Make sure we don't pass inference variables to uninhabitedness checks in borrowck
+
+struct Command<'s> {
+    session: &'s (),
+    imp: std::convert::Infallible,
+}
+
+fn command(_: &()) -> Command<'_> {
+    unreachable!()
+}
+
+fn with_session<'s>(a: &std::process::Command, b: &'s ()) -> Command<'s> {
+    a.get_program();
+    command(b)
+}