Merge #5858

5858: Draft: Show reason for failed rename refactoring r=rherrmann a=rherrmann

Return an error with a meaningful message for requests to
`textDocument/rename` if the operation cannot be performed.
Pass errors, raised by rename handling code to the LSP runtime.

As a consequence, the VS Code client shows and logs the request
as if a server-side programming error occured.
Screenshot of a rename error showing in VS Code
![invalid-rename-ui](https://user-images.githubusercontent.com/607182/91059560-2c08a380-e62a-11ea-9297-f092db935a3b.png)

I would kindly ask to get feedback from the maintainers if they can spare the time:
* Is the general direction of the proposed changes acceptable?
* I'm new to Rust. The code feels clumsy and redundant, please suggest improvements
if you find the time for. E.g. is there a simple replacement for `RenameError`?
* Should presenting the error with proper severity (i.e. not as a programming error) be part of this change or in a followup change?

See https://github.com/rust-analyzer/rust-analyzer/issues/3981

Co-authored-by: Rüdiger Herrmann <[email protected]>

1 files changed, 4 insertions, 2 deletions

diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index 57f3581b6..d54c06b14 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -77,7 +77,9 @@ pub use crate::{
     hover::{HoverAction, HoverConfig, HoverGotoTypeData, HoverResult},
     inlay_hints::{InlayHint, InlayHintsConfig, InlayKind},
     markup::Markup,
-    references::{Declaration, Reference, ReferenceAccess, ReferenceKind, ReferenceSearchResult},
+    references::{
+        Declaration, Reference, ReferenceAccess, ReferenceKind, ReferenceSearchResult, RenameError,
+    },
     runnables::{Runnable, RunnableKind, TestId},
     syntax_highlighting::{
         Highlight, HighlightModifier, HighlightModifiers, HighlightTag, HighlightedRange,
@@ -490,7 +492,7 @@ impl Analysis {
         &self,
         position: FilePosition,
         new_name: &str,
-    ) -> Cancelable<Option<RangeInfo<SourceChange>>> {
+    ) -> Cancelable<Result<RangeInfo<SourceChange>, RenameError>> {
         self.with_db(|db| references::rename(db, position, new_name))
     }