From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- .../method-mut-self-modifies-mut-slice-lvalue.rs | 44 ++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 src/test/ui/methods/method-mut-self-modifies-mut-slice-lvalue.rs (limited to 'src/test/ui/methods/method-mut-self-modifies-mut-slice-lvalue.rs') diff --git a/src/test/ui/methods/method-mut-self-modifies-mut-slice-lvalue.rs b/src/test/ui/methods/method-mut-self-modifies-mut-slice-lvalue.rs new file mode 100644 index 000000000..daff037b2 --- /dev/null +++ b/src/test/ui/methods/method-mut-self-modifies-mut-slice-lvalue.rs @@ -0,0 +1,44 @@ +// run-pass +// Test that an `&mut self` method, when invoked on a place whose +// type is `&mut [u8]`, passes in a pointer to the place and not a +// temporary. Issue #19147. + +use std::slice; +use std::cmp; + +trait MyWriter { + fn my_write(&mut self, buf: &[u8]) -> Result<(), ()>; +} + +impl<'a> MyWriter for &'a mut [u8] { + fn my_write(&mut self, buf: &[u8]) -> Result<(), ()> { + let amt = cmp::min(self.len(), buf.len()); + self[..amt].clone_from_slice(&buf[..amt]); + + let write_len = buf.len(); + unsafe { + *self = slice::from_raw_parts_mut( + self.as_mut_ptr().add(write_len), + self.len() - write_len + ); + } + + Ok(()) + } +} + +fn main() { + let mut buf = [0; 6]; + + { + let mut writer: &mut [_] = &mut buf; + writer.my_write(&[0, 1, 2]).unwrap(); + writer.my_write(&[3, 4, 5]).unwrap(); + } + + // If `my_write` is not modifying `buf` in place, then we will + // wind up with `[3, 4, 5, 0, 0, 0]` because the first call to + // `my_write()` doesn't update the starting point for the write. + + assert_eq!(buf, [0, 1, 2, 3, 4, 5]); +} -- cgit v1.2.3