From 2c1dbed4aa049d5bb5b7d83d3c856519ee27a1dc Mon Sep 17 00:00:00 2001
From: DaniPopes <57450786+DaniPopes@users.noreply.github.com>
Date: Wed, 25 Oct 2023 01:05:26 +0200
Subject: [PATCH 1/2] Print variadic argument pattern in HIR pretty printer

---
 compiler/rustc_hir_pretty/src/lib.rs | 19 ++++++++++++-------
 tests/pretty/hir-fn-variadic.pp      | 15 +++++++++++++++
 tests/pretty/hir-fn-variadic.rs      | 13 +++++++++++++
 3 files changed, 40 insertions(+), 7 deletions(-)
 create mode 100644 tests/pretty/hir-fn-variadic.pp
 create mode 100644 tests/pretty/hir-fn-variadic.rs

diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index ab6ab391484..1ce6bb6ca15 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -502,13 +502,13 @@ fn print_item(&mut self, item: &hir::Item<'_>) {
                 self.word(";");
                 self.end(); // end the outer cbox
             }
-            hir::ItemKind::Fn(ref sig, param_names, body) => {
+            hir::ItemKind::Fn(ref sig, generics, body) => {
                 self.head("");
                 self.print_fn(
                     sig.decl,
                     sig.header,
                     Some(item.ident.name),
-                    param_names,
+                    generics,
                     &[],
                     Some(body),
                 );
@@ -1948,11 +1948,10 @@ fn print_fn(
         self.print_generic_params(generics.params);
 
         self.popen();
-        let mut i = 0;
         // Make sure we aren't supplied *both* `arg_names` and `body_id`.
         assert!(arg_names.is_empty() || body_id.is_none());
-        self.commasep(Inconsistent, decl.inputs, |s, ty| {
-            s.ibox(INDENT_UNIT);
+        let mut i = 0;
+        let mut print_arg = |s: &mut Self| {
             if let Some(arg_name) = arg_names.get(i) {
                 s.word(arg_name.to_string());
                 s.word(":");
@@ -1963,11 +1962,17 @@ fn print_fn(
                 s.space();
             }
             i += 1;
+        };
+        self.commasep(Inconsistent, decl.inputs, |s, ty| {
+            s.ibox(INDENT_UNIT);
+            print_arg(s);
             s.print_type(ty);
-            s.end()
+            s.end();
         });
         if decl.c_variadic {
-            self.word(", ...");
+            self.word(", ");
+            print_arg(self);
+            self.word("...");
         }
         self.pclose();
 
diff --git a/tests/pretty/hir-fn-variadic.pp b/tests/pretty/hir-fn-variadic.pp
new file mode 100644
index 00000000000..d4fadb254a6
--- /dev/null
+++ b/tests/pretty/hir-fn-variadic.pp
@@ -0,0 +1,15 @@
+// pretty-compare-only
+// pretty-mode:hir
+// pp-exact:hir-fn-variadic.pp
+
+#![feature(c_variadic)]
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+
+extern "C" {
+    fn foo(x: i32, ...);
+}
+
+unsafe extern "C" fn bar(_: i32, mut va2: ...) -> usize { va2.arg::<usize>() }
diff --git a/tests/pretty/hir-fn-variadic.rs b/tests/pretty/hir-fn-variadic.rs
new file mode 100644
index 00000000000..efb2754df62
--- /dev/null
+++ b/tests/pretty/hir-fn-variadic.rs
@@ -0,0 +1,13 @@
+// pretty-compare-only
+// pretty-mode:hir
+// pp-exact:hir-fn-variadic.pp
+
+#![feature(c_variadic)]
+
+extern "C" {
+    pub fn foo(x: i32, va1: ...);
+}
+
+pub unsafe extern "C" fn bar(_: i32, mut va2: ...) -> usize {
+    va2.arg::<usize>()
+}

From 6aead74ff276d249c2461962ebc3bad3ad93c955 Mon Sep 17 00:00:00 2001
From: DaniPopes <57450786+DaniPopes@users.noreply.github.com>
Date: Wed, 25 Oct 2023 17:44:17 +0200
Subject: [PATCH 2/2] Remove unnecessary CVarArgs name skipping logic

---
 compiler/rustc_ast_lowering/src/lib.rs | 9 +--------
 tests/pretty/hir-fn-variadic.pp        | 2 +-
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 1e51449e70c..f48c5fc1af5 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1737,14 +1737,7 @@ fn lower_opaque_inner(
     }
 
     fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> &'hir [Ident] {
-        // Skip the `...` (`CVarArgs`) trailing arguments from the AST,
-        // as they are not explicit in HIR/Ty function signatures.
-        // (instead, the `c_variadic` flag is set to `true`)
-        let mut inputs = &decl.inputs[..];
-        if decl.c_variadic() {
-            inputs = &inputs[..inputs.len() - 1];
-        }
-        self.arena.alloc_from_iter(inputs.iter().map(|param| match param.pat.kind {
+        self.arena.alloc_from_iter(decl.inputs.iter().map(|param| match param.pat.kind {
             PatKind::Ident(_, ident, _) => self.lower_ident(ident),
             _ => Ident::new(kw::Empty, self.lower_span(param.pat.span)),
         }))
diff --git a/tests/pretty/hir-fn-variadic.pp b/tests/pretty/hir-fn-variadic.pp
index d4fadb254a6..577d9400ad4 100644
--- a/tests/pretty/hir-fn-variadic.pp
+++ b/tests/pretty/hir-fn-variadic.pp
@@ -9,7 +9,7 @@ use ::std::prelude::rust_2015::*;
 extern crate std;
 
 extern "C" {
-    fn foo(x: i32, ...);
+    fn foo(x: i32, va1: ...);
 }
 
 unsafe extern "C" fn bar(_: i32, mut va2: ...) -> usize { va2.arg::<usize>() }