Auto merge of #137294 - m-ou-se:fmt-args-2025, r=<try>

Experiment: New format_args!() representation

// TODO: description

Author: bors

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

@@ -160,6 +160,13 @@ impl FormatArgumentKind {
             &Self::Captured(id) => Some(id),
         }
     }
+
+    pub fn is_captured(&self) -> bool {
+        match self {
+            Self::Captured(_) => true,
+            _ => false,
+        }
+    }
 }
 
 #[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq)]
@@ -266,7 +273,7 @@ pub enum FormatAlignment {
 #[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq)]
 pub enum FormatCount {
     /// `{:5}` or `{:.5}`
-    Literal(usize),
+    Literal(u16),
     /// `{:.*}`, `{:.5$}`, or `{:a$}`, etc.
     Argument(FormatArgPosition),
 }

Diff for: compiler/rustc_ast_lowering/messages.ftl

@@ -175,6 +175,9 @@ 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_array_length_unstable =
     using `_` for array lengths is unstable
 

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

@@ -467,3 +467,10 @@ pub(crate) struct UseConstGenericArg {
     #[suggestion_part(code = "{other_args}")]
     pub call_args: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(ast_lowering_too_many_format_arguments)]
+pub(crate) struct TooManyFormatArguments {
+    #[primary_span]
+    pub span: Span,
+}

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

@@ -2129,12 +2129,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
         self.arena.alloc(self.expr(sp, hir::ExprKind::Tup(&[])))
     }
 
-    pub(super) fn expr_usize(&mut self, sp: Span, value: usize) -> hir::Expr<'hir> {
+    pub(super) fn expr_u64(&mut self, sp: Span, value: u64) -> hir::Expr<'hir> {
         let lit = self.arena.alloc(hir::Lit {
             span: sp,
             node: ast::LitKind::Int(
-                (value as u128).into(),
-                ast::LitIntType::Unsigned(ast::UintTy::Usize),
+                u128::from(value).into(),
+                ast::LitIntType::Unsigned(ast::UintTy::U64),
             ),
         });
         self.expr(sp, hir::ExprKind::Lit(lit))
@@ -2151,8 +2151,14 @@ 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) });
+    pub(super) fn expr_usize(&mut self, sp: Span, value: u16) -> hir::Expr<'hir> {
+        let lit = self.arena.alloc(hir::Lit {
+            span: sp,
+            node: ast::LitKind::Int(
+                u128::from(value).into(),
+                ast::LitIntType::Unsigned(ast::UintTy::Usize),
+            ),
+        });
         self.expr(sp, hir::ExprKind::Lit(lit))
     }
 
@@ -2281,6 +2287,22 @@ impl<'hir> LoweringContext<'_, 'hir> {
         self.expr(b.span, hir::ExprKind::Block(b, None))
     }
 
+    pub(super) fn expr_unsafe_block(
+        &mut self,
+        span: Span,
+        expr: &'hir hir::Expr<'hir>,
+    ) -> hir::Expr<'hir> {
+        let hir_id = self.next_id();
+        self.expr_block(self.arena.alloc(hir::Block {
+            stmts: &[],
+            expr: Some(expr),
+            hir_id,
+            rules: hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::CompilerGenerated),
+            span,
+            targeted_by_break: false,
+        }))
+    }
+
     pub(super) fn expr_array_ref(
         &mut self,
         span: Span,