Blacklist fn item types from being used with variadic functions.

src/librustc_typeck/check/mod.rs

@@ -2578,24 +2578,33 @@ fn check_argument_types<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
                 ty::TyFloat(ast::FloatTy::F32) => {
                     fcx.type_error_message(arg.span,
                                            |t| {
-                        format!("can't pass an {} to variadic \
-                                 function, cast to c_double", t)
+                        format!("can't pass an `{}` to variadic \
+                                 function, cast to `c_double`", t)
                     }, arg_ty, None);
                 }
                 ty::TyInt(ast::IntTy::I8) | ty::TyInt(ast::IntTy::I16) | ty::TyBool => {
                     fcx.type_error_message(arg.span, |t| {
-                        format!("can't pass {} to variadic \
-                                 function, cast to c_int",
+                        format!("can't pass `{}` to variadic \
+                                 function, cast to `c_int`",
                                        t)
                     }, arg_ty, None);
                 }
                 ty::TyUint(ast::UintTy::U8) | ty::TyUint(ast::UintTy::U16) => {
                     fcx.type_error_message(arg.span, |t| {
-                        format!("can't pass {} to variadic \
-                                 function, cast to c_uint",
+                        format!("can't pass `{}` to variadic \
+                                 function, cast to `c_uint`",
                                        t)
                     }, arg_ty, None);
                 }
+                ty::TyFnDef(_, _, f) => {
+                    let ptr_ty = fcx.tcx().mk_ty(ty::TyFnPtr(f));
+                    let ptr_ty = fcx.infcx().resolve_type_vars_if_possible(&ptr_ty);
+                    fcx.type_error_message(arg.span,
+                                           |t| {
+                        format!("can't pass `{}` to variadic \
+                                 function, cast to `{}`", t, ptr_ty)
+                    }, arg_ty, None);
+                }
                 _ => {}
             }
         }

src/test/compile-fail/issue-32201.rs

@@ -0,0 +1,22 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+extern {
+    fn foo(a: i32, ...);
+}
+
+fn bar(_: *const u8) {}
+
+fn main() {
+    unsafe {
+        foo(0, bar);
+        //~^ ERROR can't pass `fn(*const u8) {bar}` to variadic function, cast to `fn(*const u8)`
+    }
+}

src/test/compile-fail/variadic-ffi-3.rs

@@ -33,11 +33,11 @@ fn main() {
         //~| expected variadic fn
         //~| found non-variadic function
 
-        foo(1, 2, 3f32); //~ ERROR: can't pass an f32 to variadic function, cast to c_double
-        foo(1, 2, true); //~ ERROR: can't pass bool to variadic function, cast to c_int
-        foo(1, 2, 1i8); //~ ERROR: can't pass i8 to variadic function, cast to c_int
-        foo(1, 2, 1u8); //~ ERROR: can't pass u8 to variadic function, cast to c_uint
-        foo(1, 2, 1i16); //~ ERROR: can't pass i16 to variadic function, cast to c_int
-        foo(1, 2, 1u16); //~ ERROR: can't pass u16 to variadic function, cast to c_uint
+        foo(1, 2, 3f32); //~ ERROR: can't pass an `f32` to variadic function, cast to `c_double`
+        foo(1, 2, true); //~ ERROR: can't pass `bool` to variadic function, cast to `c_int`
+        foo(1, 2, 1i8); //~ ERROR: can't pass `i8` to variadic function, cast to `c_int`
+        foo(1, 2, 1u8); //~ ERROR: can't pass `u8` to variadic function, cast to `c_uint`
+        foo(1, 2, 1i16); //~ ERROR: can't pass `i16` to variadic function, cast to `c_int`
+        foo(1, 2, 1u16); //~ ERROR: can't pass `u16` to variadic function, cast to `c_uint`
     }
 }