parse: Tweak the function parameter edition check

src/librustc_parse/parser/item.rs

@@ -1544,9 +1544,7 @@ impl<'a> Parser<'a> {
 
         let is_name_required = match self.token.kind {
             token::DotDotDot => false,
-            // FIXME: Consider using interpolated token for this edition check,
-            // it should match the intent of edition hygiene better.
-            _ => req_name(self.token.uninterpolate().span.edition()),
+            _ => req_name(self.token.span.edition()),
         };
         let (pat, ty) = if is_name_required || self.is_named_param() {
             debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);

src/test/ui/anon-params/anon-params-edition-hygiene.rs

@@ -0,0 +1,10 @@
+// check-pass
+// edition:2018
+// aux-build:anon-params-edition-hygiene.rs
+
+#[macro_use]
+extern crate anon_params_edition_hygiene;
+
+generate_trait_2015!(u8);
+
+fn main() {}

src/test/ui/anon-params/auxiliary/anon-params-edition-hygiene.rs

@@ -0,0 +1,12 @@
+// edition:2015
+
+#[macro_export]
+macro_rules! generate_trait_2015 {
+    ($Type: ident) => {
+        trait Trait {
+            fn method($Type) {}
+        }
+    };
+}
+
+fn main() {}