From f7156cb0aeaba8fe32c381a2d676b35d2c86f46f Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Mon, 15 Mar 2021 15:38:50 +0300
Subject: Simplify source maps for fields

---
 crates/hir_def/src/body.rs       | 19 ++++++++++++++++---
 crates/hir_def/src/body/lower.rs | 24 +++++++++---------------
 2 files changed, 25 insertions(+), 18 deletions(-)

(limited to 'crates/hir_def/src')

diff --git a/crates/hir_def/src/body.rs b/crates/hir_def/src/body.rs
index 19c4eb521..8bcc350ce 100644
--- a/crates/hir_def/src/body.rs
+++ b/crates/hir_def/src/body.rs
@@ -253,11 +253,18 @@ pub type LabelSource = InFile<LabelPtr>;
 pub struct BodySourceMap {
     expr_map: FxHashMap<ExprSource, ExprId>,
     expr_map_back: ArenaMap<ExprId, Result<ExprSource, SyntheticSyntax>>,
+
     pat_map: FxHashMap<PatSource, PatId>,
     pat_map_back: ArenaMap<PatId, Result<PatSource, SyntheticSyntax>>,
+
     label_map: FxHashMap<LabelSource, LabelId>,
     label_map_back: ArenaMap<LabelId, LabelSource>,
-    field_map: FxHashMap<(ExprId, usize), InFile<AstPtr<ast::RecordExprField>>>,
+
+    /// We don't create explicit nodes for record fields (`S { record_field: 92 }`).
+    /// Instead, we use id of expression (`92`) to identify the field.
+    field_map: FxHashMap<InFile<AstPtr<ast::RecordExprField>>, ExprId>,
+    field_map_back: FxHashMap<ExprId, InFile<AstPtr<ast::RecordExprField>>>,
+
     expansions: FxHashMap<InFile<AstPtr<ast::MacroCall>>, HirFileId>,
 
     /// Diagnostics accumulated during body lowering. These contain `AstPtr`s and so are stored in
@@ -337,6 +344,8 @@ impl Index<LabelId> for Body {
     }
 }
 
+// FIXME: Change `node_` prefix to something more reasonable.
+// Perhaps `expr_syntax` and `expr_id`?
 impl BodySourceMap {
     pub fn expr_syntax(&self, expr: ExprId) -> Result<ExprSource, SyntheticSyntax> {
         self.expr_map_back[expr].clone()
@@ -375,8 +384,12 @@ impl BodySourceMap {
         self.label_map.get(&src).cloned()
     }
 
-    pub fn field_syntax(&self, expr: ExprId, field: usize) -> InFile<AstPtr<ast::RecordExprField>> {
-        self.field_map[&(expr, field)].clone()
+    pub fn field_syntax(&self, expr: ExprId) -> InFile<AstPtr<ast::RecordExprField>> {
+        self.field_map_back[&expr].clone()
+    }
+    pub fn node_field(&self, node: InFile<&ast::RecordExprField>) -> Option<ExprId> {
+        let src = node.map(|it| AstPtr::new(it));
+        self.field_map.get(&src).cloned()
     }
 
     pub(crate) fn add_diagnostics(&self, _db: &dyn DefDatabase, sink: &mut DiagnosticSink<'_>) {
diff --git a/crates/hir_def/src/body/lower.rs b/crates/hir_def/src/body/lower.rs
index 8c8eb8007..8934ae6c9 100644
--- a/crates/hir_def/src/body/lower.rs
+++ b/crates/hir_def/src/body/lower.rs
@@ -379,23 +379,22 @@ impl ExprCollector<'_> {
             }
             ast::Expr::RecordExpr(e) => {
                 let path = e.path().and_then(|path| self.expander.parse_path(path));
-                let mut field_ptrs = Vec::new();
                 let record_lit = if let Some(nfl) = e.record_expr_field_list() {
                     let fields = nfl
                         .fields()
-                        .inspect(|field| field_ptrs.push(AstPtr::new(field)))
                         .filter_map(|field| {
                             self.check_cfg(&field)?;
 
                             let name = field.field_name()?.as_name();
 
-                            Some(RecordLitField {
-                                name,
-                                expr: match field.expr() {
-                                    Some(e) => self.collect_expr(e),
-                                    None => self.missing_expr(),
-                                },
-                            })
+                            let expr = match field.expr() {
+                                Some(e) => self.collect_expr(e),
+                                None => self.missing_expr(),
+                            };
+                            let src = self.expander.to_source(AstPtr::new(&field));
+                            self.source_map.field_map.insert(src.clone(), expr);
+                            self.source_map.field_map_back.insert(expr, src);
+                            Some(RecordLitField { name, expr })
                         })
                         .collect();
                     let spread = nfl.spread().map(|s| self.collect_expr(s));
@@ -404,12 +403,7 @@ impl ExprCollector<'_> {
                     Expr::RecordLit { path, fields: Vec::new(), spread: None }
                 };
 
-                let res = self.alloc_expr(record_lit, syntax_ptr);
-                for (i, ptr) in field_ptrs.into_iter().enumerate() {
-                    let src = self.expander.to_source(ptr);
-                    self.source_map.field_map.insert((res, i), src);
-                }
-                res
+                self.alloc_expr(record_lit, syntax_ptr)
             }
             ast::Expr::FieldExpr(e) => {
                 let expr = self.collect_expr_opt(e.expr());
-- 
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