try adding a test that LowerHex and friends don't panic, but it doesn't work

1 files changed, 24 insertions, 0 deletions

diff --git a/tests/codegen/fmt_int_no_panic.rs b/tests/codegen/fmt_int_no_panic.rs
new file mode 100644
index 00000000000..efd0530bc88
--- /dev/null
+++ b/tests/codegen/fmt_int_no_panic.rs
@@ -0,0 +1,24 @@
+// Trying to check that formatting u8/u32/u64/etc do not panic.
+//
+// This test does not correctly do so yet.
+
+//@ compile-flags: -O
+
+#![crate_type = "lib"]
+
+// expected to need to write some kind of `impl core::fmt::Write` on a struct like this to avoid
+// unrelated panics if `String::write_str` can't make space..
+// struct CanAlwaysBeWrittenTo;
+
+use std::fmt::Write;
+
+// CHECK-LABEL: @format_int_doesnt_panic
+#[no_mangle]
+pub fn format_int_doesnt_panic(s: &mut String) -> std::fmt::Result {
+    // CHECK-NOT: panic
+    // ... but wait! this will definitely panic if `s.vec.reserve_for_push()` cannot alloc! this
+    // shouldn't pass!
+    write!(s, "{:x}", 0u8)?;
+    write!(s, "{:x}", u8::MAX)?;
+    Ok(())
+}