From fd52d721e1ed9794048d63e546f43805d24d7ab8 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Sun, 17 Nov 2019 20:15:55 +0300
Subject: More correct expansion mapping

We can't really map arbitrary ranges, we only can map tokens
---
 crates/ra_hir_expand/src/lib.rs | 44 ++++++++++++++++++++++++++++-------------
 1 file changed, 30 insertions(+), 14 deletions(-)

(limited to 'crates/ra_hir_expand')

diff --git a/crates/ra_hir_expand/src/lib.rs b/crates/ra_hir_expand/src/lib.rs
index 5927a03ba..57e2e6cb1 100644
--- a/crates/ra_hir_expand/src/lib.rs
+++ b/crates/ra_hir_expand/src/lib.rs
@@ -18,8 +18,9 @@ use std::sync::Arc;
 
 use ra_db::{salsa, CrateId, FileId};
 use ra_syntax::{
+    algo,
     ast::{self, AstNode},
-    SyntaxNode, TextRange, TextUnit,
+    SyntaxNode, SyntaxToken, TextRange, TextUnit,
 };
 
 use crate::ast_id_map::FileAstId;
@@ -83,13 +84,21 @@ impl HirFileId {
                     loc.def.ast_id.to_node(db).token_tree()?.syntax().text_range().start();
 
                 let macro_def = db.macro_def(loc.def)?;
-                let exp_map = db.parse_macro(macro_file)?.1;
+                let (parse, exp_map) = db.parse_macro(macro_file)?;
+                let expanded = Source::new(self, parse.syntax_node());
                 let macro_arg = db.macro_arg(macro_file.macro_call_id)?;
 
                 let arg_start = (loc.ast_id.file_id, arg_start);
                 let def_start = (loc.def.ast_id.file_id, def_start);
 
-                Some(ExpansionInfo { arg_start, def_start, macro_arg, macro_def, exp_map })
+                Some(ExpansionInfo {
+                    expanded,
+                    arg_start,
+                    def_start,
+                    macro_arg,
+                    macro_def,
+                    exp_map,
+                })
             }
         }
     }
@@ -146,27 +155,34 @@ impl MacroCallId {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
 /// ExpansionInfo mainly describes how to map text range between src and expanded macro
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ExpansionInfo {
-    pub(crate) arg_start: (HirFileId, TextUnit),
-    pub(crate) def_start: (HirFileId, TextUnit),
+    expanded: Source<SyntaxNode>,
+    arg_start: (HirFileId, TextUnit),
+    def_start: (HirFileId, TextUnit),
 
-    pub(crate) macro_def: Arc<(db::TokenExpander, mbe::TokenMap)>,
-    pub(crate) macro_arg: Arc<(tt::Subtree, mbe::TokenMap)>,
-    pub(crate) exp_map: Arc<mbe::RevTokenMap>,
+    macro_def: Arc<(db::TokenExpander, mbe::TokenMap)>,
+    macro_arg: Arc<(tt::Subtree, mbe::TokenMap)>,
+    exp_map: Arc<mbe::RevTokenMap>,
 }
 
 impl ExpansionInfo {
-    pub fn translate_offset(&self, offset: TextUnit) -> Option<TextUnit> {
-        let offset = offset.checked_sub(self.arg_start.1)?;
-        let token_id = self.macro_arg.1.token_by_offset(offset)?;
+    pub fn map_token_down(&self, token: Source<&SyntaxToken>) -> Option<Source<SyntaxToken>> {
+        assert_eq!(token.file_id, self.arg_start.0);
+        let range = token.ast.text_range().checked_sub(self.arg_start.1)?;
+        let token_id = self.macro_arg.1.token_by_range(range)?;
         let token_id = self.macro_def.0.map_id_down(token_id);
 
-        let (r, _) = self.exp_map.ranges.iter().find(|(_, tid)| *tid == token_id)?;
-        Some(r.start())
+        let range = self.exp_map.range_by_token(token_id)?;
+
+        let token = algo::find_covering_element(&self.expanded.ast, range).into_token()?;
+
+        Some(self.expanded.with_ast(token))
     }
 
+    // FIXME: a more correct signature would be
+    // `pub fn map_token_up(&self, token: Source<&SyntaxToken>) -> Option<Source<SyntaxToken>>`
     pub fn find_range(&self, from: TextRange) -> Option<(HirFileId, TextRange)> {
         let token_id = look_in_rev_map(&self.exp_map, from)?;
 
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