From aba56ddd05d821b6f0a3e5fc05bc47311e09051c Mon Sep 17 00:00:00 2001 From: "Zack M. Davis" Date: Sun, 19 Nov 2017 11:25:35 -0800 Subject: type error method suggestions use whitelisted identity-like conversions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Previously, on a type mismatch (and if this wasn't preëmpted by a higher-priority suggestion), we would look for argumentless methods returning the expected type, and list them in a `help` note. This had two major shortcomings. Firstly, a lot of the suggestions didn't really make sense (if you used a &str where a String was expected, `.to_ascii_uppercase()` is probably not the solution you were hoping for). Secondly, we weren't generating suggestions from the most useful traits! We address the first problem with an internal `#[rustc_conversion_suggestion]` attribute meant to mark methods that keep the "same value" in the relevant sense, just converting the type. We address the second problem by making `FnCtxt.probe_for_return_type` pass the `ProbeScope::AllTraits` to `probe_op`: this would seem to be safe because grep reveals no other callers of `probe_for_return_type`. Also, structured suggestions are preferred (because they're pretty, but also for RLS and friends). Also also, we make the E0055 autoderef recursion limit error use the one-time-diagnostics set, because we can potentially hit the limit a lot during probing. (Without this, test/ui/did_you_mean/recursion_limit_deref.rs would report "aborting due to 51 errors"). Unfortunately, the trait probing is still not all one would hope for: at a minimum, we don't know how to rule out `into()` in cases where it wouldn't actually work, and we don't know how to rule in `.to_owned()` where it would. Issues #46459 and #46460 have been filed and are ref'd in a FIXME. This is hoped to resolve #42929, #44672, and #45777. --- src/libstd/lib.rs | 2 +- src/libstd/path.rs | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) (limited to 'src/libstd') diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs index 29ea87aaf78..0d4e310480d 100644 --- a/src/libstd/lib.rs +++ b/src/libstd/lib.rs @@ -229,7 +229,7 @@ // Turn warnings into errors, but only after stage0, where it can be useful for // code to emit warnings during language transitions -#![deny(warnings)] +#![cfg_attr(not(stage0), deny(warnings))] // std may use features in a platform-specific way #![allow(unused_features)] diff --git a/src/libstd/path.rs b/src/libstd/path.rs index bed9efcb846..6328e4a8447 100644 --- a/src/libstd/path.rs +++ b/src/libstd/path.rs @@ -1702,6 +1702,7 @@ impl Path { /// let path_buf = Path::new("foo.txt").to_path_buf(); /// assert_eq!(path_buf, std::path::PathBuf::from("foo.txt")); /// ``` + #[rustc_conversion_suggestion] #[stable(feature = "rust1", since = "1.0.0")] pub fn to_path_buf(&self) -> PathBuf { PathBuf::from(self.inner.to_os_string()) -- cgit 1.4.1-3-g733a5