From b17bcc02b69f92a57ed7a0f94eb2cab2647fa47b Mon Sep 17 00:00:00 2001
From: Slanterns <slanterns.w@gmail.com>
Date: Sun, 16 Jun 2024 06:33:35 +0800
Subject: [PATCH] add codegen test for `Error::provide`

---
 tests/codegen/error-provide.rs | 46 ++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 tests/codegen/error-provide.rs

diff --git a/tests/codegen/error-provide.rs b/tests/codegen/error-provide.rs
new file mode 100644
index 0000000000000..63548b566cf83
--- /dev/null
+++ b/tests/codegen/error-provide.rs
@@ -0,0 +1,46 @@
+//@ compile-flags: -O
+#![crate_type = "lib"]
+#![feature(error_generic_member_access)]
+use std::error::Request;
+use std::fmt;
+
+#[derive(Debug)]
+struct MyBacktrace1 {}
+
+#[derive(Debug)]
+struct MyBacktrace2 {}
+
+#[derive(Debug)]
+struct MyBacktrace3 {}
+
+#[derive(Debug)]
+struct MyError {
+    backtrace1: MyBacktrace1,
+    backtrace2: MyBacktrace2,
+    backtrace3: MyBacktrace3,
+    other: MyBacktrace3,
+}
+
+impl fmt::Display for MyError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Example Error")
+    }
+}
+
+impl std::error::Error for MyError {
+    // CHECK-LABEL: @provide
+    #[no_mangle]
+    fn provide<'a>(&'a self, request: &mut Request<'a>) {
+        // LLVM should be able to optimize multiple .provide_* calls into a switch table and eliminate redundant ones,
+        // rather than compare one-by-one.
+
+        // CHECK: switch {{i32|i64}} %{{.*}}, label %{{.*}} [
+        // CHECK-COUNT-3: {{i32|i64}} {{.*}}, label %{{.*}}
+        // CHECK-NEXT: ]
+        request
+            .provide_ref::<MyBacktrace1>(&self.backtrace1)
+            .provide_ref::<MyBacktrace3>(&self.other)
+            .provide_ref::<MyBacktrace2>(&self.backtrace2)
+            .provide_ref::<MyBacktrace3>(&self.backtrace3);
+    }
+}