From e17f91dd8b49a319ec034a6d738e7b396e3ec879 Mon Sep 17 00:00:00 2001
From: Deadbeef <ent3rm4n@gmail.com>
Date: Fri, 26 Jan 2024 23:53:51 +0800
Subject: [PATCH] Classify closure arguments in refutable pattern in argument
 error

---
 .../rustc_mir_build/src/thir/pattern/check_match.rs   | 11 ++++++++++-
 .../pattern/usefulness/refutable-pattern-in-fn-arg.rs |  2 +-
 .../usefulness/refutable-pattern-in-fn-arg.stderr     |  2 +-
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index ce75a2831a51e..435ea3dc3bbc7 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -47,9 +47,18 @@ pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), Err
     };
     visitor.visit_expr(&thir[expr]);
 
+    let origin = match tcx.def_kind(def_id) {
+        DefKind::AssocFn | DefKind::Fn => "function argument",
+        DefKind::Closure => "closure argument",
+        // other types of MIR don't have function parameters, and we don't need to
+        // categorize those for the irrefutable check.
+        _ if thir.params.is_empty() => "",
+        kind => bug!("unexpected function parameters in THIR: {kind:?} {def_id:?}"),
+    };
+
     for param in thir.params.iter() {
         if let Some(box ref pattern) = param.pat {
-            visitor.check_binding_is_irrefutable(pattern, "function argument", None, None);
+            visitor.check_binding_is_irrefutable(pattern, origin, None, None);
         }
     }
     visitor.error
diff --git a/tests/ui/pattern/usefulness/refutable-pattern-in-fn-arg.rs b/tests/ui/pattern/usefulness/refutable-pattern-in-fn-arg.rs
index 4203dd94d43aa..51ff641509df5 100644
--- a/tests/ui/pattern/usefulness/refutable-pattern-in-fn-arg.rs
+++ b/tests/ui/pattern/usefulness/refutable-pattern-in-fn-arg.rs
@@ -1,6 +1,6 @@
 fn main() {
     let f = |3: isize| println!("hello");
-    //~^ ERROR refutable pattern in function argument
+    //~^ ERROR refutable pattern in closure argument
     //~| `..=2_isize` and `4_isize..` not covered
     f(4);
 }
diff --git a/tests/ui/pattern/usefulness/refutable-pattern-in-fn-arg.stderr b/tests/ui/pattern/usefulness/refutable-pattern-in-fn-arg.stderr
index bd6c5002e63e8..be119d27ab254 100644
--- a/tests/ui/pattern/usefulness/refutable-pattern-in-fn-arg.stderr
+++ b/tests/ui/pattern/usefulness/refutable-pattern-in-fn-arg.stderr
@@ -1,4 +1,4 @@
-error[E0005]: refutable pattern in function argument
+error[E0005]: refutable pattern in closure argument
   --> $DIR/refutable-pattern-in-fn-arg.rs:2:14
    |
 LL |     let f = |3: isize| println!("hello");