Create core::fmt::ArgumentV1 with generics instead of fn pointer

Author: nbdd0121

compiler/rustc_builtin_macros/src/format.rs

@@ -889,11 +889,21 @@ impl<'a, 'b> Context<'a, 'b> {
                 return ecx.expr_call_global(macsp, path, vec![arg]);
             }
         };
+        let new_fn_name = match trait_ {
+            "Display" => "new_display",
+            "Debug" => "new_debug",
+            "LowerExp" => "new_lower_exp",
+            "UpperExp" => "new_upper_exp",
+            "Octal" => "new_octal",
+            "Pointer" => "new_pointer",
+            "Binary" => "new_binary",
+            "LowerHex" => "new_lower_hex",
+            "UpperHex" => "new_upper_hex",
+            _ => unreachable!(),
+        };
 
-        let path = ecx.std_path(&[sym::fmt, Symbol::intern(trait_), sym::fmt]);
-        let format_fn = ecx.path_global(sp, path);
-        let path = ecx.std_path(&[sym::fmt, sym::ArgumentV1, sym::new]);
-        ecx.expr_call_global(macsp, path, vec![arg, ecx.expr_path(format_fn)])
+        let path = ecx.std_path(&[sym::fmt, sym::ArgumentV1, Symbol::intern(new_fn_name)]);
+        ecx.expr_call_global(macsp, path, vec![arg])
     }
 }
 

library/core/src/fmt/mod.rs

@@ -308,6 +308,16 @@ static USIZE_MARKER: fn(&usize, &mut Formatter<'_>) -> Result = |ptr, _| {
     loop {}
 };
 
+macro_rules! arg_new {
+    ($f: ident, $t: ident) => {
+        #[doc(hidden)]
+        #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+        pub fn $f<'b, T: $t>(x: &'b T) -> ArgumentV1<'_> {
+            Self::new(x, $t::fmt)
+        }
+    };
+}
+
 impl<'a> ArgumentV1<'a> {
     #[doc(hidden)]
     #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
@@ -323,6 +333,16 @@ impl<'a> ArgumentV1<'a> {
         unsafe { ArgumentV1 { formatter: mem::transmute(f), value: mem::transmute(x) } }
     }
 
+    arg_new!(new_display, Display);
+    arg_new!(new_debug, Debug);
+    arg_new!(new_octal, Octal);
+    arg_new!(new_lower_hex, LowerHex);
+    arg_new!(new_upper_hex, UpperHex);
+    arg_new!(new_pointer, Pointer);
+    arg_new!(new_binary, Binary);
+    arg_new!(new_lower_exp, LowerExp);
+    arg_new!(new_upper_exp, UpperExp);
+
     #[doc(hidden)]
     #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
     pub fn from_usize(x: &usize) -> ArgumentV1<'_> {