Rollup merge of #126101 - lqd:revert-124099, r=wesleywiser

Revert "Disallow ambiguous attributes on expressions" on nightly

As discussed in [today's t-compiler meeting](https://rust-lang.zulipchat.com/#narrow/stream/238009-t-compiler.2Fmeetings/topic/.5Bweekly.5D.202024-06-06/near/443079505), this reverts PR #124099 to fix P-critical beta regressions #125199.

r? ``@wesleywiser``

Opening as draft so that ``@wesleywiser`` and ``@apiraino,`` you can tell me whether you wanted:
1. a `beta-accepted` revert of #124099 on nightly (this PR)? That will need to be backported to beta (even though #126093 may be the last of those)
2. a revert of #124099 on beta?
3. all of the above?

I also opened #126102, another draft PR to revert #124099 on beta, should you choose options 2 or 3.

1 files changed, 13 insertions, 19 deletions

diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 1b99bc015b6..285bac3f4b8 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -328,9 +328,7 @@ impl<'a> Parser<'a> {
                 this.parse_expr_assoc_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
             })?;
 
-            self.error_ambiguous_outer_attrs(&lhs, lhs_span, rhs.span);
-            let span = lhs_span.to(rhs.span);
-
+            let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
             lhs = match op {
                 AssocOp::Add
                 | AssocOp::Subtract
@@ -429,18 +427,6 @@ impl<'a> Parser<'a> {
         });
     }
 
-    fn error_ambiguous_outer_attrs(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) {
-        if let Some(attr) = lhs.attrs.iter().find(|a| a.style == AttrStyle::Outer) {
-            self.dcx().emit_err(errors::AmbiguousOuterAttributes {
-                span: attr.span.to(rhs_span),
-                sugg: errors::WrapInParentheses::Expression {
-                    left: attr.span.shrink_to_lo(),
-                    right: lhs_span.shrink_to_hi(),
-                },
-            });
-        }
-    }
-
     /// Possibly translate the current token to an associative operator.
     /// The method does not advance the current token.
     ///
@@ -520,8 +506,7 @@ impl<'a> Parser<'a> {
             None
         };
         let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
-        self.error_ambiguous_outer_attrs(&lhs, lhs.span, rhs_span);
-        let span = lhs.span.to(rhs_span);
+        let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
         let limits =
             if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
         let range = self.mk_range(Some(lhs), rhs, limits);
@@ -739,8 +724,7 @@ impl<'a> Parser<'a> {
         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.error_ambiguous_outer_attrs(&lhs, lhs_span, rhs.span);
-            this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs))
+            this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, rhs.span), expr_kind(lhs, rhs))
         };
 
         // Save the state of the parser before parsing type normally, in case there is a
@@ -3858,6 +3842,16 @@ impl<'a> Parser<'a> {
         self.mk_expr(span, ExprKind::Err(guar))
     }
 
+    /// 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 {
+        lhs.attrs
+            .iter()
+            .find(|a| a.style == AttrStyle::Outer)
+            .map_or(lhs_span, |a| a.span)
+            .to(rhs_span)
+    }
+
     fn collect_tokens_for_expr(
         &mut self,
         attrs: AttrWrapper,