3 files changed, 43 insertions, 30 deletions
diff --git a/compiler/rustc_parse/src/parser/attr.rs b/compiler/rustc_parse/src/parser/attr.rs
index 02dab95233a..a92609c2c2f 100644
--- a/compiler/rustc_parse/src/parser/attr.rs
+++ b/compiler/rustc_parse/src/parser/attr.rs
@@ -1,4 +1,7 @@
-use crate::errors::{InvalidMetaItem, SuffixedLiteralInAttribute};
+use crate::errors::{
+    InvalidMetaItem, InvalidMetaItemSuggQuoteIdent, InvalidMetaItemUnquotedIdent,
+    SuffixedLiteralInAttribute,
+};
 use crate::fluent_generated as fluent;
 
 use super::{AttrWrapper, Capturing, FnParseMode, ForceCollect, Parser, PathStyle};
@@ -417,9 +420,26 @@ impl<'a> Parser<'a> {
             Err(err) => err.cancel(),
         }
 
-        Err(self
-            .dcx()
-            .create_err(InvalidMetaItem { span: self.token.span, token: self.token.clone() }))
+        let token = self.token.clone();
+
+        // Check for unquoted idents in meta items, e.g.: #[cfg(key = foo)]
+        // `from_expansion()` ensures we don't suggest for cases such as
+        // `#[cfg(feature = $expr)]` in macros
+        if self.prev_token == token::Eq && !self.token.span.from_expansion() {
+            let before = self.token.span.shrink_to_lo();
+            while matches!(self.token.kind, token::Ident(..)) {
+                self.bump();
+            }
+            let after = self.prev_token.span.shrink_to_hi();
+            let sugg = InvalidMetaItemSuggQuoteIdent { before, after };
+            return Err(self.dcx().create_err(InvalidMetaItemUnquotedIdent {
+                span: token.span,
+                token,
+                sugg,
+            }));
+        }
+
+        Err(self.dcx().create_err(InvalidMetaItem { span: token.span, token }))
     }
 }
 
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 8ca02452342..ae3661a530b 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -33,7 +33,6 @@ use rustc_session::errors::{report_lit_error, ExprParenthesesNeeded};
 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
 use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_span::source_map::{self, Spanned};
-use rustc_span::symbol::kw::PathRoot;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, Pos, Span};
 use thin_vec::{thin_vec, ThinVec};
@@ -642,26 +641,13 @@ impl<'a> Parser<'a> {
     }
 
     /// Parse `box expr` - this syntax has been removed, but we still parse this
-    /// for now to provide an automated way to fix usages of it
-    fn parse_expr_box(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
-        let (span, expr) = self.parse_expr_prefix_common(lo)?;
-        let code = self.sess.source_map().span_to_snippet(span.with_lo(lo.hi())).unwrap();
-        self.dcx().emit_err(errors::BoxSyntaxRemoved { span, code: code.trim() });
-        // So typechecking works, parse `box <expr>` as `::std::boxed::Box::new(expr)`
-        let path = Path {
-            span,
-            segments: [
-                PathSegment::from_ident(Ident::with_dummy_span(PathRoot)),
-                PathSegment::from_ident(Ident::with_dummy_span(sym::std)),
-                PathSegment::from_ident(Ident::from_str("boxed")),
-                PathSegment::from_ident(Ident::from_str("Box")),
-                PathSegment::from_ident(Ident::with_dummy_span(sym::new)),
-            ]
-            .into(),
-            tokens: None,
-        };
-        let path = self.mk_expr(span, ExprKind::Path(None, path));
-        Ok((span, self.mk_call(path, ThinVec::from([expr]))))
+    /// for now to provide a more useful error
+    fn parse_expr_box(&mut self, box_kw: Span) -> PResult<'a, (Span, ExprKind)> {
+        let (span, _) = self.parse_expr_prefix_common(box_kw)?;
+        let inner_span = span.with_lo(box_kw.hi());
+        let code = self.sess.source_map().span_to_snippet(inner_span).unwrap();
+        self.dcx().emit_err(errors::BoxSyntaxRemoved { span: span, code: code.trim() });
+        Ok((span, ExprKind::Err))
     }
 
     fn is_mistaken_not_ident_negation(&self) -> bool {
@@ -1844,7 +1830,7 @@ impl<'a> Parser<'a> {
             let lexpr = self.parse_expr_labeled(label, true)?;
             self.dcx().emit_err(errors::LabeledLoopInBreak {
                 span: lexpr.span,
-                sub: errors::WrapExpressionInParentheses {
+                sub: errors::WrapInParentheses::Expression {
                     left: lexpr.span.shrink_to_lo(),
                     right: lexpr.span.shrink_to_hi(),
                 },
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 1a8bbf0a157..1bae5b32240 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -389,7 +389,7 @@ impl<'a> Parser<'a> {
                 self.dcx().emit_err(errors::InvalidExpressionInLetElse {
                     span: init.span,
                     operator: op.node.as_str(),
-                    sugg: errors::WrapExpressionInParentheses {
+                    sugg: errors::WrapInParentheses::Expression {
                         left: init.span.shrink_to_lo(),
                         right: init.span.shrink_to_hi(),
                     },
@@ -400,12 +400,19 @@ impl<'a> Parser<'a> {
 
     fn check_let_else_init_trailing_brace(&self, init: &ast::Expr) {
         if let Some(trailing) = classify::expr_trailing_brace(init) {
-            self.dcx().emit_err(errors::InvalidCurlyInLetElse {
-                span: trailing.span.with_lo(trailing.span.hi() - BytePos(1)),
-                sugg: errors::WrapExpressionInParentheses {
+            let sugg = match &trailing.kind {
+                ExprKind::MacCall(mac) => errors::WrapInParentheses::MacroArgs {
+                    left: mac.args.dspan.open,
+                    right: mac.args.dspan.close,
+                },
+                _ => errors::WrapInParentheses::Expression {
                     left: trailing.span.shrink_to_lo(),
                     right: trailing.span.shrink_to_hi(),
                 },
+            };
+            self.dcx().emit_err(errors::InvalidCurlyInLetElse {
+                span: trailing.span.with_lo(trailing.span.hi() - BytePos(1)),
+                sugg,
             });
         }
     }