Add a note to the ArbitraryExpressionInPattern error

2 files changed, 7 insertions, 1 deletions

diff --git a/compiler/rustc_ast_lowering/src/errors.rs b/compiler/rustc_ast_lowering/src/errors.rs
index 6f70e135c72..02744d16b42 100644
--- a/compiler/rustc_ast_lowering/src/errors.rs
+++ b/compiler/rustc_ast_lowering/src/errors.rs
@@ -368,6 +368,8 @@ pub struct NeverPatternWithGuard {
 pub struct ArbitraryExpressionInPattern {
     #[primary_span]
     pub span: Span,
+    #[note(ast_lowering_pattern_from_macro_note)]
+    pub pattern_from_macro_note: bool,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index 118a7322fbd..32de07a0755 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -339,7 +339,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             ExprKind::Path(..) if allow_paths => {}
             ExprKind::Unary(UnOp::Neg, inner) if matches!(inner.kind, ExprKind::Lit(_)) => {}
             _ => {
-                let guar = self.dcx().emit_err(ArbitraryExpressionInPattern { span: expr.span });
+                let pattern_from_macro = expr.is_approximately_pattern();
+                let guar = self.dcx().emit_err(ArbitraryExpressionInPattern {
+                    span: expr.span,
+                    pattern_from_macro_note: pattern_from_macro,
+                });
                 return self.arena.alloc(self.expr_err(expr.span, guar));
             }
         }