New fmt::Arguments implementation.

Author: m-ou-se

compiler/rustc_ast_lowering/messages.ftl

@@ -169,6 +169,9 @@ ast_lowering_template_modifier = template modifier
 
 ast_lowering_this_not_async = this is not `async`
 
+ast_lowering_too_many_format_arguments =
+    too many arguments used in format string
+
 ast_lowering_underscore_expr_lhs_assign =
     in expressions, `_` can only be used on the left-hand side of an assignment
     .label = `_` not allowed here

compiler/rustc_ast_lowering/src/errors.rs

@@ -475,3 +475,10 @@ pub(crate) struct UnionWithDefault {
     #[primary_span]
     pub span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(ast_lowering_too_many_format_arguments)]
+pub(crate) struct TooManyFormatArguments {
+    #[primary_span]
+    pub span: Span,
+}

compiler/rustc_ast_lowering/src/expr.rs

@@ -2105,18 +2105,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         self.expr(sp, hir::ExprKind::Lit(lit))
     }
 
-    pub(super) fn expr_usize(&mut self, sp: Span, value: usize) -> hir::Expr<'hir> {
+    pub(super) fn expr_usize(&mut self, sp: Span, value: u64) -> hir::Expr<'hir> {
         self.expr_uint(sp, ast::UintTy::Usize, value as u128)
     }
 
-    pub(super) fn expr_u32(&mut self, sp: Span, value: u32) -> hir::Expr<'hir> {
-        self.expr_uint(sp, ast::UintTy::U32, value as u128)
-    }
-
-    pub(super) fn expr_u16(&mut self, sp: Span, value: u16) -> hir::Expr<'hir> {
-        self.expr_uint(sp, ast::UintTy::U16, value as u128)
-    }
-
     pub(super) fn expr_str(&mut self, sp: Span, value: Symbol) -> hir::Expr<'hir> {
         let lit = hir::Lit {
             span: self.lower_span(sp),