Pretty print attributes in print_arg

src/libsyntax/print/pprust.rs

@@ -2639,27 +2639,23 @@ impl<'a> State<'a> {
         self.s.word("<");
 
         self.commasep(Inconsistent, &generic_params, |s, param| {
+            s.print_outer_attributes_inline(&param.attrs);
+
             match param.kind {
                 ast::GenericParamKind::Lifetime => {
-                    s.print_outer_attributes_inline(&param.attrs);
                     let lt = ast::Lifetime { id: param.id, ident: param.ident };
                     s.print_lifetime_bounds(lt, &param.bounds)
                 }
                 ast::GenericParamKind::Type { ref default } => {
-                    s.print_outer_attributes_inline(&param.attrs);
                     s.print_ident(param.ident);
                     s.print_type_bounds(":", &param.bounds);
-                    match default {
-                        Some(ref default) => {
-                            s.s.space();
-                            s.word_space("=");
-                            s.print_type(default)
-                        }
-                        _ => {}
+                    if let Some(ref default) = default {
+                        s.s.space();
+                        s.word_space("=");
+                        s.print_type(default)
                     }
                 }
                 ast::GenericParamKind::Const { ref ty } => {
-                    s.print_outer_attributes_inline(&param.attrs);
                     s.word_space("const");
                     s.print_ident(param.ident);
                     s.s.space();
@@ -2760,6 +2756,9 @@ impl<'a> State<'a> {
 
     crate fn print_arg(&mut self, input: &ast::Arg, is_closure: bool) {
         self.ibox(INDENT_UNIT);
+
+        self.print_outer_attributes_inline(&input.attrs);
+
         match input.ty.node {
             ast::TyKind::Infer if is_closure => self.print_pat(&input.pat),
             _ => {

src/test/ui/rfc-2565-param-attrs/auxiliary/param-attrs.rs

@@ -0,0 +1,34 @@
+// force-host
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+macro_rules! checker {
+    ($attr_name:ident, $expected:literal) => {
+        #[proc_macro_attribute]
+        pub fn $attr_name(attr: TokenStream, input: TokenStream) -> TokenStream {
+            assert!(attr.to_string().is_empty());
+            assert_eq!(input.to_string(), $expected);
+            TokenStream::new()
+        }
+    }
+}
+
+checker!(attr_extern, r#"extern "C" {
+    fn ffi(#[a1] arg1: i32, #[a2] ...);
+}"#);
+checker!(attr_extern_cvar, r#"unsafe extern "C" fn cvar(arg1: i32, #[a1] mut args: ...) { }"#);
+checker!(attr_alias, "type Alias = fn(#[a1] u8, #[a2] ...);");
+checker!(attr_free, "fn free(#[a1] arg1: u8) { let lam = |#[a2] W(x), #[a3] y| (); }");
+checker!(attr_inherent_1, "fn inherent1(#[a1] self, #[a2] arg1: u8) { }");
+checker!(attr_inherent_2, "fn inherent2(#[a1] &self, #[a2] arg1: u8) { }");
+checker!(attr_inherent_3, "fn inherent3<'a>(#[a1] &'a mut self, #[a2] arg1: u8) { }");
+checker!(attr_inherent_4, "fn inherent4<'a>(#[a1] self: Box<Self>, #[a2] arg1: u8) { }");
+checker!(attr_trait_1, "fn trait1(#[a1] self, #[a2] arg1: u8);");
+checker!(attr_trait_2, "fn trait2(#[a1] &self, #[a2] arg1: u8);");
+checker!(attr_trait_3, "fn trait3<'a>(#[a1] &'a mut self, #[a2] arg1: u8);");
+checker!(attr_trait_4, "fn trait4<'a>(#[a1] self: Box<Self>, #[a2] arg1: u8, #[a3] Vec<u8>);");

src/test/ui/rfc-2565-param-attrs/param-attrs-pretty.rs

@@ -0,0 +1,56 @@
+// aux-build:param-attrs.rs
+
+// check-pass
+
+#![feature(param_attrs)]
+#![feature(c_variadic)]
+
+extern crate param_attrs;
+
+use param_attrs::*;
+
+struct W(u8);
+
+#[attr_extern]
+extern "C" { fn ffi(#[a1] arg1: i32, #[a2] ...); }
+
+#[attr_extern_cvar]
+unsafe extern "C" fn cvar(arg1: i32, #[a1] mut args: ...) {}
+
+#[attr_alias]
+type Alias = fn(#[a1] u8, #[a2] ...);
+
+#[attr_free]
+fn free(#[a1] arg1: u8) {
+    let lam = |#[a2] W(x), #[a3] y| ();
+}
+
+impl W {
+    #[attr_inherent_1]
+    fn inherent1(#[a1] self, #[a2] arg1: u8) {}
+
+    #[attr_inherent_2]
+    fn inherent2(#[a1] &self, #[a2] arg1: u8) {}
+
+    #[attr_inherent_3]
+    fn inherent3<'a>(#[a1] &'a mut self, #[a2] arg1: u8) {}
+
+    #[attr_inherent_4]
+    fn inherent4<'a>(#[a1] self: Box<Self>, #[a2] arg1: u8) {}
+}
+
+trait A {
+    #[attr_trait_1]
+    fn trait1(#[a1] self, #[a2] arg1: u8);
+
+    #[attr_trait_2]
+    fn trait2(#[a1] &self, #[a2] arg1: u8);
+
+    #[attr_trait_3]
+    fn trait3<'a>(#[a1] &'a mut self, #[a2] arg1: u8);
+
+    #[attr_trait_4]
+    fn trait4<'a>(#[a1] self: Box<Self>, #[a2] arg1: u8, #[a3] Vec<u8>);
+}
+
+fn main() {}