Merge #3656

3656: Simplify arenas r=matklad a=matklad

At the moment, Arena is paranetrized by two types: index and data. The original motivation was to allow index to be defined in the downstream crate, so that you can add inherent impls to the index. 

However, it seems like we've never actually used that capability, so perhaps we should switch to a generic Index impl? This PR tries this out, switching only `raw.rs` and parts of `hir_def`. 

wdyt?

Co-authored-by: Aleksey Kladov <[email protected]>

1 files changed, 3 insertions, 5 deletions

diff --git a/crates/ra_hir_expand/src/ast_id_map.rs b/crates/ra_hir_expand/src/ast_id_map.rs
index a764bdf24..a6644d55f 100644
--- a/crates/ra_hir_expand/src/ast_id_map.rs
+++ b/crates/ra_hir_expand/src/ast_id_map.rs
@@ -10,7 +10,7 @@ use std::{
     marker::PhantomData,
 };
 
-use ra_arena::{impl_arena_id, Arena, RawId};
+use ra_arena::{Arena, Idx};
 use ra_syntax::{ast, AstNode, AstPtr, SyntaxNode, SyntaxNodePtr};
 
 /// `AstId` points to an AST node in a specific file.
@@ -49,14 +49,12 @@ impl<N: AstNode> FileAstId<N> {
     }
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-struct ErasedFileAstId(RawId);
-impl_arena_id!(ErasedFileAstId);
+type ErasedFileAstId = Idx<SyntaxNodePtr>;
 
 /// Maps items' `SyntaxNode`s to `ErasedFileAstId`s and back.
 #[derive(Debug, PartialEq, Eq, Default)]
 pub struct AstIdMap {
-    arena: Arena<ErasedFileAstId, SyntaxNodePtr>,
+    arena: Arena<SyntaxNodePtr>,
 }
 
 impl AstIdMap {