From 8170acb197d7658505949cefc12e01dfc4c8feab Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Wed, 19 Jun 2024 16:24:21 +1000
Subject: [PATCH] Refactor `parse_expr_res`.

This removes the final `Option<AttrWrapper>` argument.
---
 .../rustc_parse/src/parser/diagnostics.rs     | 13 ++++++--
 compiler/rustc_parse/src/parser/expr.rs       | 30 ++++++++++++-------
 compiler/rustc_parse/src/parser/mod.rs        | 11 -------
 compiler/rustc_parse/src/parser/path.rs       |  3 +-
 compiler/rustc_parse/src/parser/stmt.rs       |  4 +--
 5 files changed, 33 insertions(+), 28 deletions(-)

diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 2bb6fb53869b..17e62a8e0468 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -2502,7 +2502,8 @@ pub(super) fn handle_ambiguous_unbraced_const_arg(
     /// wrapped in braces.
     pub(super) fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
         let start = self.token.span;
-        let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
+        let attrs = self.parse_outer_attributes()?;
+        let expr = self.parse_expr_res(Restrictions::CONST_EXPR, attrs).map_err(|mut err| {
             err.span_label(
                 start.shrink_to_lo(),
                 "while parsing a const generic argument starting here",
@@ -2624,7 +2625,10 @@ pub(super) fn recover_const_arg(
         if is_op_or_dot {
             self.bump();
         }
-        match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
+        match (|| {
+            let attrs = self.parse_outer_attributes()?;
+            self.parse_expr_res(Restrictions::CONST_EXPR, attrs)
+        })() {
             Ok(expr) => {
                 // Find a mistake like `MyTrait<Assoc == S::Assoc>`.
                 if token::EqEq == snapshot.token.kind {
@@ -2678,7 +2682,10 @@ pub(crate) fn recover_unbraced_const_arg_that_can_begin_ty(
         &mut self,
         mut snapshot: SnapshotParser<'a>,
     ) -> Option<P<ast::Expr>> {
-        match snapshot.parse_expr_res(Restrictions::CONST_EXPR, None) {
+        match (|| {
+            let attrs = self.parse_outer_attributes()?;
+            snapshot.parse_expr_res(Restrictions::CONST_EXPR, attrs)
+        })() {
             // Since we don't know the exact reason why we failed to parse the type or the
             // expression, employ a simple heuristic to weed out some pathological cases.
             Ok(expr) if let token::Comma | token::Gt = snapshot.token.kind => {
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index aea04ceca914..d27c612bbc1e 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -94,7 +94,8 @@ impl<'a> Parser<'a> {
     pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
         self.current_closure.take();
 
-        self.parse_expr_res(Restrictions::empty(), None)
+        let attrs = self.parse_outer_attributes()?;
+        self.parse_expr_res(Restrictions::empty(), attrs)
     }
 
     /// Parses an expression, forcing tokens to be collected
@@ -107,7 +108,8 @@ pub fn parse_expr_anon_const(&mut self) -> PResult<'a, AnonConst> {
     }
 
     fn parse_expr_catch_underscore(&mut self, restrictions: Restrictions) -> PResult<'a, P<Expr>> {
-        match self.parse_expr_res(restrictions, None) {
+        let attrs = self.parse_outer_attributes()?;
+        match self.parse_expr_res(restrictions, attrs) {
             Ok(expr) => Ok(expr),
             Err(err) => match self.token.ident() {
                 Some((Ident { name: kw::Underscore, .. }, IdentIsRaw::No))
@@ -134,9 +136,8 @@ fn parse_expr_paren_seq(&mut self) -> PResult<'a, ThinVec<P<Expr>>> {
     pub(super) fn parse_expr_res(
         &mut self,
         r: Restrictions,
-        attrs: Option<AttrWrapper>,
+        attrs: AttrWrapper,
     ) -> PResult<'a, P<Expr>> {
-        let attrs = self.parse_or_use_outer_attributes(attrs)?;
         self.with_res(r, |this| this.parse_expr_assoc_with(0, LhsExpr::Unparsed { attrs }))
     }
 
@@ -2343,7 +2344,8 @@ fn parse_expr_closure(&mut self) -> PResult<'a, P<Expr>> {
                     self.restrictions - Restrictions::STMT_EXPR - Restrictions::ALLOW_LET;
                 let prev = self.prev_token.clone();
                 let token = self.token.clone();
-                match self.parse_expr_res(restrictions, None) {
+                let attrs = self.parse_outer_attributes()?;
+                match self.parse_expr_res(restrictions, attrs) {
                     Ok(expr) => expr,
                     Err(err) => self.recover_closure_body(err, before, prev, token, lo, decl_hi)?,
                 }
@@ -2591,8 +2593,9 @@ fn parse_if_after_cond(&mut self, lo: Span, mut cond: P<Expr>) -> PResult<'a, P<
 
     /// Parses the condition of a `if` or `while` expression.
     fn parse_expr_cond(&mut self) -> PResult<'a, P<Expr>> {
+        let attrs = self.parse_outer_attributes()?;
         let mut cond =
-            self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, None)?;
+            self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, attrs)?;
 
         CondChecker::new(self).visit_expr(&mut cond);
 
@@ -2776,7 +2779,8 @@ fn parse_for_head(&mut self) -> PResult<'a, (P<Pat>, P<Expr>)> {
             (Err(err), Some((start_span, left))) if self.eat_keyword(kw::In) => {
                 // We know for sure we have seen `for ($SOMETHING in`. In the happy path this would
                 // happen right before the return of this method.
-                let expr = match self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None) {
+                let attrs = self.parse_outer_attributes()?;
+                let expr = match self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, attrs) {
                     Ok(expr) => expr,
                     Err(expr_err) => {
                         // We don't know what followed the `in`, so cancel and bubble up the
@@ -2810,7 +2814,8 @@ fn parse_for_head(&mut self) -> PResult<'a, (P<Pat>, P<Expr>)> {
             self.error_missing_in_for_loop();
         }
         self.check_for_for_in_in_typo(self.prev_token.span);
-        let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+        let attrs = self.parse_outer_attributes()?;
+        let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, attrs)?;
         Ok((pat, expr))
     }
 
@@ -2922,7 +2927,8 @@ pub(crate) fn eat_label(&mut self) -> Option<Label> {
     /// Parses a `match ... { ... }` expression (`match` token already eaten).
     fn parse_expr_match(&mut self) -> PResult<'a, P<Expr>> {
         let match_span = self.prev_token.span;
-        let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+        let attrs = self.parse_outer_attributes()?;
+        let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, attrs)?;
 
         self.parse_match_block(match_span, match_span, scrutinee, MatchKind::Prefix)
     }
@@ -3126,8 +3132,9 @@ pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
                 let arrow_span = this.prev_token.span;
                 let arm_start_span = this.token.span;
 
+                let attrs = this.parse_outer_attributes()?;
                 let expr =
-                    this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
+                    this.parse_expr_res(Restrictions::STMT_EXPR, attrs).map_err(|mut err| {
                         err.span_label(arrow_span, "while parsing the `match` arm starting here");
                         err
                     })?;
@@ -3332,7 +3339,8 @@ fn parse_match_arm_pat_and_guard(&mut self) -> PResult<'a, (P<Pat>, Option<P<Exp
     }
 
     fn parse_match_guard_condition(&mut self) -> PResult<'a, P<Expr>> {
-        self.parse_expr_res(Restrictions::ALLOW_LET | Restrictions::IN_IF_GUARD, None).map_err(
+        let attrs = self.parse_outer_attributes()?;
+        self.parse_expr_res(Restrictions::ALLOW_LET | Restrictions::IN_IF_GUARD, attrs).map_err(
             |mut err| {
                 if self.prev_token == token::OpenDelim(Delimiter::Brace) {
                     let sugg_sp = self.prev_token.span.shrink_to_lo();
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index adf04fcf2241..f4cab480669b 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -1337,17 +1337,6 @@ fn parse_delim_args_inner(&mut self) -> Option<DelimArgs> {
         })
     }
 
-    fn parse_or_use_outer_attributes(
-        &mut self,
-        already_parsed_attrs: Option<AttrWrapper>,
-    ) -> PResult<'a, AttrWrapper> {
-        if let Some(attrs) = already_parsed_attrs {
-            Ok(attrs)
-        } else {
-            self.parse_outer_attributes()
-        }
-    }
-
     /// Parses a single token tree from the input.
     pub fn parse_token_tree(&mut self) -> TokenTree {
         match self.token.kind {
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index 9beecd9849fb..da8d1194325b 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -920,7 +920,8 @@ pub(super) fn parse_generic_arg(
             // Fall back by trying to parse a const-expr expression. If we successfully do so,
             // then we should report an error that it needs to be wrapped in braces.
             let snapshot = self.create_snapshot_for_diagnostic();
-            match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
+            let attrs = self.parse_outer_attributes()?;
+            match self.parse_expr_res(Restrictions::CONST_EXPR, attrs) {
                 Ok(expr) => {
                     return Ok(Some(self.dummy_const_arg_needs_braces(
                         self.dcx().struct_span_err(expr.span, "invalid const generic expression"),
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 8684f2ed829d..d65f6ff68eee 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -126,9 +126,9 @@ pub fn parse_stmt_without_recovery(
             // Remainder are line-expr stmts.
             let e = match force_collect {
                 ForceCollect::Yes => self.collect_tokens_no_attrs(|this| {
-                    this.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
+                    this.parse_expr_res(Restrictions::STMT_EXPR, attrs)
                 })?,
-                ForceCollect::No => self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))?,
+                ForceCollect::No => self.parse_expr_res(Restrictions::STMT_EXPR, attrs)?,
             };
             if matches!(e.kind, ExprKind::Assign(..)) && self.eat_keyword(kw::Else) {
                 let bl = self.parse_block()?;