Auto merge of #73996 - da-x:short-unique-paths, r=petrochenkov

diagnostics: shorten paths of unique symbols

This is a step towards implementing a fix for #50310, and continuation of the discussion in [Pre-RFC: Nicer Types In Diagnostics - compiler - Rust Internals](https://internals.rust-lang.org/t/pre-rfc-nicer-types-in-diagnostics/11139). Impressed upon me from previous discussion in #21934 that an RFC for this is not needed, and I should just come up with code.

The recent improvements to `use` suggestions that I've contributed have given rise to this implementation. Contrary to previous suggestions, it's rather simple logic, and I believe it only reduces the amount of cognitive load that a developer would need when reading type errors.

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If a symbol name can only be imported from one place, and as long as it was not glob-imported anywhere in the current crate, we can trim its printed path to the last component.

This has wide implications on error messages with types, for example, shortening `std::vec::Vec` to just `Vec`, as long as there is no other `Vec` importable from anywhere.

1 files changed, 1 insertions, 0 deletions

diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index ada8dc90494..dc4fa807f78 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -518,6 +518,7 @@ fn test_debugging_options_tracking_hash() {
     untracked!(time_llvm_passes, true);
     untracked!(time_passes, true);
     untracked!(trace_macros, true);
+    untracked!(trim_diagnostic_paths, false);
     untracked!(ui_testing, true);
     untracked!(unpretty, Some("expanded".to_string()));
     untracked!(unstable_options, true);