add check if macro from expansion

Author: Kivooeo

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -942,6 +942,11 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
  err.span_label(block.span, "this empty block is missing a tail expression");
  return;
  };
+ // FIXME expr and stmt have the same span if expr comes from expansion
+ // cc: https://github.com/rust-lang/rust/pull/147416#discussion_r2499407523
+ if stmt.span.from_expansion() {
+ return;
+ }
  let hir::StmtKind::Semi(tail_expr) = stmt.kind else {
  return;
  };

tests/ui/macros/macro-expansion-empty-span-147255.rs

@@ -0,0 +1,10 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/147255>
+
+fn main() {
+ let mut x = 4;
+ let x_str = {
+ format!("{}", x);
+ //()
+ };
+ println!("{}", x_str); //~ ERROR `()` doesn't implement `std::fmt::Display`
+}

tests/ui/macros/macro-expansion-empty-span-147255.stderr

@@ -0,0 +1,15 @@
+error[E0277]: `()` doesn't implement `std::fmt::Display`
+ --> $DIR/macro-expansion-empty-span-147255.rs:9:20
+ |
+LL | println!("{}", x_str);
+ | -- ^^^^^ `()` cannot be formatted with the default formatter
+ | |
+ | required by this formatting parameter
+ |
+ = help: the trait `std::fmt::Display` is not implemented for `()`
+ = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
+ = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.