Use simplified formatting flags in fmt::Arguments.

Author: m-ou-se

Diff for: compiler/rustc_ast_lowering/src/expr.rs

@@ -2162,11 +2162,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
         self.expr(sp, hir::ExprKind::Lit(lit))
     }
 
-    pub(super) fn expr_char(&mut self, sp: Span, value: char) -> hir::Expr<'hir> {
-        let lit = self.arena.alloc(hir::Lit { span: sp, node: ast::LitKind::Char(value) });
-        self.expr(sp, hir::ExprKind::Lit(lit))
-    }
-
     pub(super) fn expr_str(&mut self, sp: Span, value: Symbol) -> hir::Expr<'hir> {
         let lit = self
             .arena

Diff for: compiler/rustc_ast_lowering/src/format.rs

@@ -361,24 +361,25 @@ fn make_format_spec<'hir>(
         zero_pad,
         debug_hex,
     } = &placeholder.format_options;
-    let fill = ctx.expr_char(sp, fill.unwrap_or(' '));
-    let align = ctx.expr_lang_item_type_relative(
-        sp,
-        hir::LangItem::FormatAlignment,
-        match alignment {
-            Some(FormatAlignment::Left) => sym::Left,
-            Some(FormatAlignment::Right) => sym::Right,
-            Some(FormatAlignment::Center) => sym::Center,
-            None => sym::Unknown,
-        },
-    );
-    // This needs to match `Flag` in library/core/src/fmt/rt.rs.
+    let fill = fill.unwrap_or(' ');
+    // These need to match the constants in library/core/src/fmt/rt.rs.
+    let align = match alignment {
+        Some(FormatAlignment::Left) => 0,
+        Some(FormatAlignment::Right) => 1,
+        Some(FormatAlignment::Center) => 2,
+        None => 3,
+    };
+    // This needs to match the constants in library/core/src/fmt/rt.rs.
     let flags: u32 = ((sign == Some(FormatSign::Plus)) as u32)
         | ((sign == Some(FormatSign::Minus)) as u32) << 1
         | (alternate as u32) << 2
         | (zero_pad as u32) << 3
         | ((debug_hex == Some(FormatDebugHex::Lower)) as u32) << 4
-        | ((debug_hex == Some(FormatDebugHex::Upper)) as u32) << 5;
+        | ((debug_hex == Some(FormatDebugHex::Upper)) as u32) << 5
+        | align << 6
+        | (width.is_some() as u32) << 8
+        | (precision.is_some() as u32) << 9
+        | (fill as u32) << 11;
     let flags = ctx.expr_u32(sp, flags);
     let precision = make_count(ctx, sp, precision, argmap);
     let width = make_count(ctx, sp, width, argmap);
@@ -387,7 +388,7 @@ fn make_format_spec<'hir>(
         hir::LangItem::FormatPlaceholder,
         sym::new,
     ));
-    let args = ctx.arena.alloc_from_iter([position, fill, align, flags, precision, width]);
+    let args = ctx.arena.alloc_from_iter([position, flags, precision, width]);
     ctx.expr_call_mut(sp, format_placeholder_new, args)
 }
 

Diff for: compiler/rustc_hir/src/lang_items.rs

@@ -321,7 +321,6 @@ language_item_table! {
     BeginPanic,              sym::begin_panic,         begin_panic_fn,             Target::Fn,             GenericRequirement::None;
 
     // Lang items needed for `format_args!()`.
-    FormatAlignment,         sym::format_alignment,    format_alignment,           Target::Enum,           GenericRequirement::None;
     FormatArgument,          sym::format_argument,     format_argument,            Target::Struct,         GenericRequirement::None;
     FormatArguments,         sym::format_arguments,    format_arguments,           Target::Struct,         GenericRequirement::None;
     FormatCount,             sym::format_count,        format_count,               Target::Enum,           GenericRequirement::None;

Diff for: compiler/rustc_span/src/symbol.rs

@@ -975,7 +975,6 @@ symbols! {
         forbid,
         forget,
         format,
-        format_alignment,
         format_args,
         format_args_capture,
         format_args_macro,