Auto merge of #56999 - petrochenkov:macrecov2, r=estebank

AST/HIR: Introduce `ExprKind::Err` for better error recovery in the front-end

This way we can avoid aborting compilation if expansion produces errors and generate `ExprKind::Err`s instead.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 931e91e9c79..2ad3d3a6d64 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1093,7 +1093,9 @@ impl<'a> State<'a> {
                 self.s.word("_")?;
             }
             ast::TyKind::Err => {
-                self.s.word("?")?;
+                self.popen()?;
+                self.s.word("/*ERROR*/")?;
+                self.pclose()?;
             }
             ast::TyKind::ImplicitSelf => {
                 self.s.word("Self")?;
@@ -2391,6 +2393,11 @@ impl<'a> State<'a> {
                 self.s.space()?;
                 self.print_block_with_attrs(blk, attrs)?
             }
+            ast::ExprKind::Err => {
+                self.popen()?;
+                self.s.word("/*ERROR*/")?;
+                self.pclose()?
+            }
         }
         self.ann.post(self, AnnNode::Expr(expr))?;
         self.end()