[WIP] Benchmark span combining changes

Author: petrochenkov

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -743,9 +743,11 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, '_, 'tcx> {
         // or
         // `fn foo(&x: &i32)` -> `fn foo(&(mut x): &i32)`
         let def_id = self.body.source.def_id();
-        if let Some(local_def_id) = def_id.as_local()
-            && let Some(body) = self.infcx.tcx.hir().maybe_body_owned_by(local_def_id)
-            && let Some(hir_id) = (BindingFinder { span: pat_span }).visit_body(&body).break_value()
+        let hir_id = def_id
+            .as_local()
+            .and_then(|def_id| self.infcx.tcx.hir().maybe_body_owned_by(def_id))
+            .and_then(|body| (BindingFinder { span: pat_span }).visit_body(&body).break_value());
+        if let Some(hir_id) = hir_id
             && let node = self.infcx.tcx.hir_node(hir_id)
             && let hir::Node::LetStmt(hir::LetStmt {
                 pat: hir::Pat { kind: hir::PatKind::Ref(_, _), .. },
@@ -767,8 +769,11 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, '_, 'tcx> {
             return;
         }
 
+        let span = local_decl.source_info.span;
+        let span =
+            hir_id.map_or(span, |hir_id| span.with_neighbor(self.infcx.tcx.hir().span(hir_id)));
         err.span_suggestion_verbose(
-            local_decl.source_info.span.shrink_to_lo(),
+            span.shrink_to_lo(),
             "consider changing this to be mutable",
             "mut ",
             Applicability::MachineApplicable,

compiler/rustc_expand/src/mbe/transcribe.rs

@@ -395,9 +395,22 @@ fn maybe_use_metavar_location(
         return orig_tt.clone();
     }
 
-    let insert = |mspans: &mut FxHashMap<_, _>, s, ms| match mspans.try_insert(s, ms) {
+    let insert = |mspans: &mut FxHashMap<_, _>, s, ms: Span| match mspans.try_insert(s, ms) {
         Ok(_) => true,
-        Err(err) => *err.entry.get() == ms, // Tried to insert the same span, still success
+        Err(mut err) => {
+            let old_ms = *err.entry.get();
+            if ms == old_ms {
+                // Tried to insert the same span, still success.
+                return true;
+            }
+            if !ms.eq_ctxt(old_ms) && ms.ctxt().outer_expn_data().call_site.eq_ctxt(old_ms) {
+                // This looks like a variable passed to an inner (possibly recursive) macro call.
+                // The innermost metavar span is the most useful, so override.
+                err.entry.insert(ms);
+                return true;
+            }
+            false
+        }
     };
     marker.visit_span(&mut metavar_span);
     let no_collision = match orig_tt {
@@ -411,16 +424,19 @@ fn maybe_use_metavar_location(
         }),
     };
     if no_collision || psess.source_map().is_imported(metavar_span) {
+        if let TokenTree::Token(token, _) = orig_tt {
+            return TokenTree::Token(token.clone(), Spacing::Alone);
+        }
         return orig_tt.clone();
     }
 
     // Setting metavar spans for the heuristic spans gives better opportunities for combining them
     // with neighboring spans even despite their different syntactic contexts.
     match orig_tt {
-        TokenTree::Token(Token { kind, span }, spacing) => {
+        TokenTree::Token(Token { kind, span }, _spacing) => {
             let span = metavar_span.with_ctxt(span.ctxt());
             with_metavar_spans(|mspans| insert(mspans, span, metavar_span));
-            TokenTree::Token(Token { kind: kind.clone(), span }, *spacing)
+            TokenTree::Token(Token { kind: kind.clone(), span }, Spacing::Alone)
         }
         TokenTree::Delimited(dspan, dspacing, delimiter, tts) => {
             let open = metavar_span.with_ctxt(dspan.open.ctxt());

compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs

@@ -56,7 +56,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             ));
         }
 
-        if self_ty.span.edition().at_least_rust_2021() {
+        if tcx.hir().span_in_context(self_ty.hir_id).edition().at_least_rust_2021() {
             let msg = "trait objects must include the `dyn` keyword";
             let label = "add `dyn` keyword before this trait";
             let mut diag =

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -2454,7 +2454,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ExprKind::Path(QPath::Resolved(_, path)) => {
                     // local binding
                     if let hir::def::Res::Local(hir_id) = path.res {
-                        let span = tcx.hir().span(hir_id);
+                        let span = tcx.hir().span_in_context(hir_id);
                         let filename = tcx.sess.source_map().span_to_filename(span);
 
                         let parent_node = self.tcx.parent_hir_node(hir_id);

compiler/rustc_lint/src/types.rs

@@ -718,8 +718,9 @@ fn lint_wide_pointer<'tcx>(
         return;
     };
 
+    let (l_span, r_span) = (l.span.with_neighbor(e.span), r.span.with_neighbor(e.span));
     let (Some(l_span), Some(r_span)) =
-        (l.span.find_ancestor_inside(e.span), r.span.find_ancestor_inside(e.span))
+        (l_span.find_ancestor_inside(e.span), r_span.find_ancestor_inside(e.span))
     else {
         return cx.emit_span_lint(
             AMBIGUOUS_WIDE_POINTER_COMPARISONS,

compiler/rustc_middle/src/hir/map/mod.rs

@@ -935,6 +935,11 @@ impl<'hir> Map<'hir> {
         }
     }
 
+    pub fn span_in_context(self, hir_id: HirId) -> Span {
+        let parent_span = self.span(self.tcx.parent_hir_id(hir_id));
+        self.span(hir_id).with_neighbor(parent_span)
+    }
+
     /// Get a representation of this `id` for debugging purposes.
     /// NOTE: Do NOT use this in diagnostics!
     pub fn node_to_string(self, id: HirId) -> String {

compiler/rustc_parse/src/parser/expr.rs

@@ -249,10 +249,11 @@ impl<'a> Parser<'a> {
                 continue;
             }
 
+            let op_span = op.span;
             let op = op.node;
             // Special cases:
             if op == AssocOp::As {
-                lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
+                lhs = self.parse_assoc_op_cast(lhs, lhs_span, op_span, ExprKind::Cast)?;
                 continue;
             } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
                 // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
@@ -274,7 +275,7 @@ impl<'a> Parser<'a> {
                 this.parse_expr_assoc_with(prec + prec_adjustment, LhsExpr::Unparsed { attrs })
             })?;
 
-            let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
+            let span = self.mk_expr_sp(&lhs, lhs_span, op_span, rhs.span);
             lhs = match op {
                 AssocOp::Add
                 | AssocOp::Subtract
@@ -453,7 +454,7 @@ impl<'a> Parser<'a> {
             None
         };
         let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
-        let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
+        let span = self.mk_expr_sp(&lhs, lhs.span, cur_op_span, rhs_span);
         let limits =
             if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
         let range = self.mk_range(Some(lhs), rhs, limits);
@@ -674,10 +675,11 @@ impl<'a> Parser<'a> {
         &mut self,
         lhs: P<Expr>,
         lhs_span: Span,
+        op_span: Span,
         expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
     ) -> PResult<'a, P<Expr>> {
         let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
-            this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, rhs.span), expr_kind(lhs, rhs))
+            this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, op_span, rhs.span), expr_kind(lhs, rhs))
         };
 
         // Save the state of the parser before parsing type normally, in case there is a
@@ -3852,11 +3854,13 @@ impl<'a> Parser<'a> {
 
     /// Create expression span ensuring the span of the parent node
     /// is larger than the span of lhs and rhs, including the attributes.
-    fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
+    fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, op_span: Span, rhs_span: Span) -> Span {
         lhs.attrs
             .iter()
             .find(|a| a.style == AttrStyle::Outer)
             .map_or(lhs_span, |a| a.span)
+            // An approximation to #126763.
+            .to(op_span)
             .to(rhs_span)
     }
 

compiler/rustc_parse/src/parser/mod.rs

@@ -687,9 +687,9 @@ impl<'a> Parser<'a> {
         self.is_keyword_ahead(0, &[kw::Const])
             && self.look_ahead(1, |t| match &t.kind {
                 // async closures do not work with const closures, so we do not parse that here.
-                token::Ident(kw::Move | kw::Static, _) | token::OrOr | token::BinOp(token::Or) => {
-                    true
-                }
+                token::Ident(kw::Move | kw::Static, IdentIsRaw::No)
+                | token::OrOr
+                | token::BinOp(token::Or) => true,
                 _ => false,
             })
     }

compiler/rustc_parse/src/parser/path.rs

@@ -211,7 +211,8 @@ impl<'a> Parser<'a> {
         if self.eat(&token::PathSep) {
             segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
         }
-        self.parse_path_segments(&mut segments, style, ty_generics)?;
+        let sep_span = self.parse_path_segments(&mut segments, style, ty_generics)?;
+        let lo = sep_span.map_or(lo, |sep_span| lo.with_neighbor(sep_span));
         Ok(Path { segments, span: lo.to(self.prev_token.span), tokens: None })
     }
 
@@ -220,7 +221,9 @@ impl<'a> Parser<'a> {
         segments: &mut ThinVec<PathSegment>,
         style: PathStyle,
         ty_generics: Option<&Generics>,
-    ) -> PResult<'a, ()> {
+    ) -> PResult<'a, Option<Span>> {
+        // An approximation to #126763.
+        let mut sep_span = None;
         loop {
             let segment = self.parse_path_segment(style, ty_generics)?;
             if style.has_generic_ambiguity() {
@@ -268,7 +271,9 @@ impl<'a> Parser<'a> {
                     continue;
                 }
 
-                return Ok(());
+                return Ok(sep_span);
+            } else {
+                sep_span = Some(self.prev_token.span);
             }
         }
     }

compiler/rustc_span/src/lib.rs

@@ -876,6 +876,7 @@ impl Span {
 
     /// Check if you can select metavar spans for the given spans to get matching contexts.
     fn try_metavars(a: SpanData, b: SpanData, a_orig: Span, b_orig: Span) -> (SpanData, SpanData) {
+        let (a_orig, b_orig) = (a_orig.with_parent(None), b_orig.with_parent(None));
         let get = |mspans: &FxHashMap<_, _>, s| mspans.get(&s).copied();
         match with_metavar_spans(|mspans| (get(mspans, a_orig), get(mspans, b_orig))) {
             (None, None) => {}
@@ -938,7 +939,7 @@ impl Span {
     pub fn with_neighbor(self, neighbor: Span) -> Span {
         match Span::prepare_to_combine(self, neighbor) {
             Ok((this, ..)) => this.span(),
-            Err(_) => self,
+            Err(fallback) => self.with_ctxt(fallback.ctxt()),
         }
     }