Do not consider using a semicolon inside of a different-crate macro

Fixes rust-lang#81943

Author: notriddle

compiler/rustc_typeck/src/check/coercion.rs

@@ -1448,7 +1448,15 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                 expected.is_unit(),
                 pointing_at_return_type,
             ) {
-                if cond_expr.span.desugaring_kind().is_none() {
+                // If the block is from a macro, then do not suggest
+                // adding a semicolon, because there's nowhere to put it.
+                // See issue #81943.
+                let hir = fcx.tcx.hir();
+                let body_owner =
+                    hir.body_owner(hir.body_owned_by(hir.enclosing_body_owner(fcx.body_id)));
+                let from_same_crate = cond_expr.span.ctxt().dollar_crate_name()
+                    == hir.span(body_owner).ctxt().dollar_crate_name();
+                if cond_expr.span.desugaring_kind().is_none() && from_same_crate {
                     err.span_label(cond_expr.span, "expected this to be `()`");
                     fcx.suggest_semicolon_at_end(cond_expr.span, &mut err);
                 }

src/test/ui/typeck/issue-81943.rs

@@ -0,0 +1,5 @@
+fn f<F: Fn(i32)>(f: F) { f(0); }
+fn main() {
+  f(|x| dbg!(x)); //~ERROR
+  f(|x| match x { tmp => { tmp } }); //~ERROR
+}

src/test/ui/typeck/issue-81943.stderr

@@ -0,0 +1,20 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-81943.rs:3:9
+   |
+LL |   f(|x| dbg!(x));
+   |         ^^^^^^^ expected `()`, found `i32`
+   |
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0308]: mismatched types
+  --> $DIR/issue-81943.rs:4:28
+   |
+LL |   f(|x| match x { tmp => { tmp } });
+   |         -------------------^^^----- help: consider using a semicolon here
+   |         |                  |
+   |         |                  expected `()`, found `i32`
+   |         expected this to be `()`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.