Transition OnEnter to WorkspaceSnippetEdit

This also changes our handiling of snippet edits on the client side.
`editor.insertSnippet` unfortunately forces indentation, which we
really don't want to have to deal with. So, let's just implement our
manual hacky way of dealing with a simple subset of snippets we
actually use in rust-analyzer

crates/rust-analyzer/src/lsp_ext.rs

@@ -102,7 +102,7 @@ pub enum OnEnter {}
 
 impl Request for OnEnter {
     type Params = lsp_types::TextDocumentPositionParams;
-    type Result = Option<SourceChange>;
+    type Result = Option<SnippetWorkspaceEdit>;
     const METHOD: &'static str = "rust-analyzer/onEnter";
 }
 

crates/rust-analyzer/src/main_loop/handlers.rs

@@ -159,12 +159,12 @@ pub fn handle_join_lines(
 pub fn handle_on_enter(
     world: WorldSnapshot,
     params: lsp_types::TextDocumentPositionParams,
-) -> Result<Option<lsp_ext::SourceChange>> {
+) -> Result<Option<lsp_ext::SnippetWorkspaceEdit>> {
     let _p = profile("handle_on_enter");
     let position = from_proto::file_position(&world, params)?;
     match world.analysis().on_enter(position)? {
         None => Ok(None),
-        Some(source_change) => to_proto::source_change(&world, source_change).map(Some),
+        Some(source_change) => to_proto::snippet_workspace_edit(&world, source_change).map(Some),
     }
 }