Merge pull request #20056 from ShoyuVanilla/fmt-args-new

Minic rustc's new `format_args!` expansion

8 files changed, 412 insertions, 46 deletions

diff --git a/src/tools/rust-analyzer/crates/hir-def/src/expr_store/lower.rs b/src/tools/rust-analyzer/crates/hir-def/src/expr_store/lower.rs
index 4ba31c1e20b..efa1374a446 100644
--- a/src/tools/rust-analyzer/crates/hir-def/src/expr_store/lower.rs
+++ b/src/tools/rust-analyzer/crates/hir-def/src/expr_store/lower.rs
@@ -2815,6 +2815,51 @@ impl ExprCollector<'_> {
                 mutability: Mutability::Shared,
             })
         };
+
+        // Assume that rustc version >= 1.89.0 iff lang item `format_arguments` exists
+        // but `format_unsafe_arg` does not
+        let fmt_args =
+            || crate::lang_item::lang_item(self.db, self.module.krate(), LangItem::FormatArguments);
+        let fmt_unsafe_arg =
+            || crate::lang_item::lang_item(self.db, self.module.krate(), LangItem::FormatUnsafeArg);
+        let use_format_args_since_1_89_0 = fmt_args().is_some() && fmt_unsafe_arg().is_none();
+
+        let idx = if use_format_args_since_1_89_0 {
+            self.collect_format_args_impl(
+                syntax_ptr,
+                fmt,
+                hygiene,
+                argmap,
+                lit_pieces,
+                format_options,
+            )
+        } else {
+            self.collect_format_args_before_1_89_0_impl(
+                syntax_ptr,
+                fmt,
+                argmap,
+                lit_pieces,
+                format_options,
+            )
+        };
+
+        self.source_map
+            .template_map
+            .get_or_insert_with(Default::default)
+            .format_args_to_captures
+            .insert(idx, (hygiene, mappings));
+        idx
+    }
+
+    /// `format_args!` expansion implementation for rustc versions < `1.89.0`
+    fn collect_format_args_before_1_89_0_impl(
+        &mut self,
+        syntax_ptr: AstPtr<ast::Expr>,
+        fmt: FormatArgs,
+        argmap: FxIndexSet<(usize, ArgumentType)>,
+        lit_pieces: ExprId,
+        format_options: ExprId,
+    ) -> ExprId {
         let arguments = &*fmt.arguments.arguments;
 
         let args = if arguments.is_empty() {
@@ -2902,19 +2947,181 @@ impl ExprCollector<'_> {
             });
         }
 
-        let idx = self.alloc_expr(
+        self.alloc_expr(
             Expr::Call {
                 callee: new_v1_formatted,
                 args: Box::new([lit_pieces, args, format_options, unsafe_arg_new]),
             },
             syntax_ptr,
-        );
-        self.source_map
-            .template_map
-            .get_or_insert_with(Default::default)
-            .format_args_to_captures
-            .insert(idx, (hygiene, mappings));
-        idx
+        )
+    }
+
+    /// `format_args!` expansion implementation for rustc versions >= `1.89.0`,
+    /// especially since [this PR](https://github.com/rust-lang/rust/pull/140748)
+    fn collect_format_args_impl(
+        &mut self,
+        syntax_ptr: AstPtr<ast::Expr>,
+        fmt: FormatArgs,
+        hygiene: HygieneId,
+        argmap: FxIndexSet<(usize, ArgumentType)>,
+        lit_pieces: ExprId,
+        format_options: ExprId,
+    ) -> ExprId {
+        let arguments = &*fmt.arguments.arguments;
+
+        let (let_stmts, args) = if arguments.is_empty() {
+            (
+                // Generate:
+                //     []
+                vec![],
+                self.alloc_expr_desugared(Expr::Array(Array::ElementList {
+                    elements: Box::default(),
+                })),
+            )
+        } else if argmap.len() == 1 && arguments.len() == 1 {
+            // Only one argument, so we don't need to make the `args` tuple.
+            //
+            // Generate:
+            //     super let args = [<core::fmt::Arguments>::new_display(&arg)];
+            let args = argmap
+                .iter()
+                .map(|&(arg_index, ty)| {
+                    let ref_arg = self.alloc_expr_desugared(Expr::Ref {
+                        expr: arguments[arg_index].expr,
+                        rawness: Rawness::Ref,
+                        mutability: Mutability::Shared,
+                    });
+                    self.make_argument(ref_arg, ty)
+                })
+                .collect();
+            let args =
+                self.alloc_expr_desugared(Expr::Array(Array::ElementList { elements: args }));
+            let args_name = Name::new_symbol_root(sym::args);
+            let args_binding =
+                self.alloc_binding(args_name.clone(), BindingAnnotation::Unannotated, hygiene);
+            let args_pat = self.alloc_pat_desugared(Pat::Bind { id: args_binding, subpat: None });
+            self.add_definition_to_binding(args_binding, args_pat);
+            // TODO: We don't have `super let` yet.
+            let let_stmt = Statement::Let {
+                pat: args_pat,
+                type_ref: None,
+                initializer: Some(args),
+                else_branch: None,
+            };
+            (vec![let_stmt], self.alloc_expr_desugared(Expr::Path(Path::from(args_name))))
+        } else {
+            // Generate:
+            //     super let args = (&arg0, &arg1, &...);
+            let args_name = Name::new_symbol_root(sym::args);
+            let args_binding =
+                self.alloc_binding(args_name.clone(), BindingAnnotation::Unannotated, hygiene);
+            let args_pat = self.alloc_pat_desugared(Pat::Bind { id: args_binding, subpat: None });
+            self.add_definition_to_binding(args_binding, args_pat);
+            let elements = arguments
+                .iter()
+                .map(|arg| {
+                    self.alloc_expr_desugared(Expr::Ref {
+                        expr: arg.expr,
+                        rawness: Rawness::Ref,
+                        mutability: Mutability::Shared,
+                    })
+                })
+                .collect();
+            let args_tuple = self.alloc_expr_desugared(Expr::Tuple { exprs: elements });
+            // TODO: We don't have `super let` yet
+            let let_stmt1 = Statement::Let {
+                pat: args_pat,
+                type_ref: None,
+                initializer: Some(args_tuple),
+                else_branch: None,
+            };
+
+            // Generate:
+            //     super let args = [
+            //         <core::fmt::Argument>::new_display(args.0),
+            //         <core::fmt::Argument>::new_lower_hex(args.1),
+            //         <core::fmt::Argument>::new_debug(args.0),
+            //         …
+            //     ];
+            let args = argmap
+                .iter()
+                .map(|&(arg_index, ty)| {
+                    let args_ident_expr =
+                        self.alloc_expr_desugared(Expr::Path(args_name.clone().into()));
+                    let arg = self.alloc_expr_desugared(Expr::Field {
+                        expr: args_ident_expr,
+                        name: Name::new_tuple_field(arg_index),
+                    });
+                    self.make_argument(arg, ty)
+                })
+                .collect();
+            let array =
+                self.alloc_expr_desugared(Expr::Array(Array::ElementList { elements: args }));
+            let args_binding =
+                self.alloc_binding(args_name.clone(), BindingAnnotation::Unannotated, hygiene);
+            let args_pat = self.alloc_pat_desugared(Pat::Bind { id: args_binding, subpat: None });
+            self.add_definition_to_binding(args_binding, args_pat);
+            let let_stmt2 = Statement::Let {
+                pat: args_pat,
+                type_ref: None,
+                initializer: Some(array),
+                else_branch: None,
+            };
+            (vec![let_stmt1, let_stmt2], self.alloc_expr_desugared(Expr::Path(args_name.into())))
+        };
+
+        // Generate:
+        //     &args
+        let args = self.alloc_expr_desugared(Expr::Ref {
+            expr: args,
+            rawness: Rawness::Ref,
+            mutability: Mutability::Shared,
+        });
+
+        let call_block = {
+            // Generate:
+            //     unsafe {
+            //         <core::fmt::Arguments>::new_v1_formatted(
+            //             lit_pieces,
+            //             args,
+            //             format_options,
+            //         )
+            //     }
+
+            let new_v1_formatted = LangItem::FormatArguments.ty_rel_path(
+                self.db,
+                self.module.krate(),
+                Name::new_symbol_root(sym::new_v1_formatted),
+            );
+            let new_v1_formatted =
+                self.alloc_expr_desugared(new_v1_formatted.map_or(Expr::Missing, Expr::Path));
+            let args = [lit_pieces, args, format_options];
+            let call = self
+                .alloc_expr_desugared(Expr::Call { callee: new_v1_formatted, args: args.into() });
+
+            Expr::Unsafe { id: None, statements: Box::default(), tail: Some(call) }
+        };
+
+        if !let_stmts.is_empty() {
+            // Generate:
+            //     {
+            //         super let …
+            //         super let …
+            //         <core::fmt::Arguments>::new_…(…)
+            //     }
+            let call = self.alloc_expr_desugared(call_block);
+            self.alloc_expr(
+                Expr::Block {
+                    id: None,
+                    statements: let_stmts.into(),
+                    tail: Some(call),
+                    label: None,
+                },
+                syntax_ptr,
+            )
+        } else {
+            self.alloc_expr(call_block, syntax_ptr)
+        }
     }
 
     /// Generate a hir expression for a format_args placeholder specification.
diff --git a/src/tools/rust-analyzer/crates/hir-def/src/expr_store/tests/body.rs b/src/tools/rust-analyzer/crates/hir-def/src/expr_store/tests/body.rs
index 29e249b07a7..927e280d739 100644
--- a/src/tools/rust-analyzer/crates/hir-def/src/expr_store/tests/body.rs
+++ b/src/tools/rust-analyzer/crates/hir-def/src/expr_store/tests/body.rs
@@ -178,14 +178,14 @@ fn main() {
 }
 
 #[test]
-fn desugar_builtin_format_args() {
+fn desugar_builtin_format_args_before_1_89_0() {
     let (db, body, def) = lower(
         r#"
-//- minicore: fmt
+//- minicore: fmt_before_1_89_0
 fn main() {
     let are = "are";
     let count = 10;
-    builtin#format_args("\u{1b}hello {count:02} {} friends, we {are:?} {0}{last}", "fancy", last = "!");
+    builtin#format_args("\u{1b}hello {count:02} {} friends, we {are:?} {0}{last}", "fancy", orphan = (), last = "!");
 }
 "#,
     );
@@ -249,8 +249,11 @@ fn main() {
                         builtin#lang(Count::Implied),
                     ),
                 ],
-                unsafe {
-                    builtin#lang(UnsafeArg::new)()
+                {
+                    ();
+                    unsafe {
+                        builtin#lang(UnsafeArg::new)()
+                    }
                 },
             );
         }"#]]
@@ -258,6 +261,89 @@ fn main() {
 }
 
 #[test]
+fn desugar_builtin_format_args() {
+    let (db, body, def) = lower(
+        r#"
+//- minicore: fmt
+fn main() {
+    let are = "are";
+    let count = 10;
+    builtin#format_args("\u{1b}hello {count:02} {} friends, we {are:?} {0}{last}", "fancy", orphan = (), last = "!");
+}
+"#,
+    );
+
+    expect![[r#"
+        fn main() {
+            let are = "are";
+            let count = 10;
+            {
+                let args = (&"fancy", &(), &"!", &count, &are, );
+                let args = [
+                    builtin#lang(Argument::new_display)(
+                        args.3,
+                    ), builtin#lang(Argument::new_display)(
+                        args.0,
+                    ), builtin#lang(Argument::new_debug)(
+                        args.4,
+                    ), builtin#lang(Argument::new_display)(
+                        args.2,
+                    ),
+                ];
+                unsafe {
+                    builtin#lang(Arguments::new_v1_formatted)(
+                        &[
+                            "\u{1b}hello ", " ", " friends, we ", " ", "",
+                        ],
+                        &args,
+                        &[
+                            builtin#lang(Placeholder::new)(
+                                0usize,
+                                ' ',
+                                builtin#lang(Alignment::Unknown),
+                                8u32,
+                                builtin#lang(Count::Implied),
+                                builtin#lang(Count::Is)(
+                                    2,
+                                ),
+                            ), builtin#lang(Placeholder::new)(
+                                1usize,
+                                ' ',
+                                builtin#lang(Alignment::Unknown),
+                                0u32,
+                                builtin#lang(Count::Implied),
+                                builtin#lang(Count::Implied),
+                            ), builtin#lang(Placeholder::new)(
+                                2usize,
+                                ' ',
+                                builtin#lang(Alignment::Unknown),
+                                0u32,
+                                builtin#lang(Count::Implied),
+                                builtin#lang(Count::Implied),
+                            ), builtin#lang(Placeholder::new)(
+                                1usize,
+                                ' ',
+                                builtin#lang(Alignment::Unknown),
+                                0u32,
+                                builtin#lang(Count::Implied),
+                                builtin#lang(Count::Implied),
+                            ), builtin#lang(Placeholder::new)(
+                                3usize,
+                                ' ',
+                                builtin#lang(Alignment::Unknown),
+                                0u32,
+                                builtin#lang(Count::Implied),
+                                builtin#lang(Count::Implied),
+                            ),
+                        ],
+                    )
+                }
+            };
+        }"#]]
+    .assert_eq(&body.pretty_print(&db, def, Edition::CURRENT))
+}
+
+#[test]
 fn test_macro_hygiene() {
     let (db, body, def) = lower(
         r##"
@@ -295,29 +381,31 @@ impl SsrError {
     expect![[r#"
         fn main() {
             _ = ra_test_fixture::error::SsrError::new(
-                builtin#lang(Arguments::new_v1_formatted)(
-                    &[
-                        "Failed to resolve path `", "`",
-                    ],
-                    &[
+                {
+                    let args = [
                         builtin#lang(Argument::new_display)(
                             &node.text(),
                         ),
-                    ],
-                    &[
-                        builtin#lang(Placeholder::new)(
-                            0usize,
-                            ' ',
-                            builtin#lang(Alignment::Unknown),
-                            0u32,
-                            builtin#lang(Count::Implied),
-                            builtin#lang(Count::Implied),
-                        ),
-                    ],
+                    ];
                     unsafe {
-                        builtin#lang(UnsafeArg::new)()
-                    },
-                ),
+                        builtin#lang(Arguments::new_v1_formatted)(
+                            &[
+                                "Failed to resolve path `", "`",
+                            ],
+                            &args,
+                            &[
+                                builtin#lang(Placeholder::new)(
+                                    0usize,
+                                    ' ',
+                                    builtin#lang(Alignment::Unknown),
+                                    0u32,
+                                    builtin#lang(Count::Implied),
+                                    builtin#lang(Count::Implied),
+                                ),
+                            ],
+                        )
+                    }
+                },
             );
         }"#]]
     .assert_eq(&body.pretty_print(&db, def, Edition::CURRENT))
@@ -327,7 +415,7 @@ impl SsrError {
 fn regression_10300() {
     let (db, body, def) = lower(
         r#"
-//- minicore: concat, panic
+//- minicore: concat, panic, fmt_before_1_89_0
 mod private {
     pub use core::concat;
 }
diff --git a/src/tools/rust-analyzer/crates/ide-assists/src/handlers/term_search.rs b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/term_search.rs
index f01b7c0bc24..019ddaf1441 100644
--- a/src/tools/rust-analyzer/crates/ide-assists/src/handlers/term_search.rs
+++ b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/term_search.rs
@@ -100,7 +100,9 @@ fn f() { let a: u128 = 1; let b: u128 = todo$0!() }"#,
     fn test_complete_todo_with_msg() {
         check_assist(
             term_search,
-            r#"//- minicore: todo, unimplemented
+            // FIXME: Since we are lacking of `super let`, term search fails due to borrowck failure.
+            // Should implement super let and remove `fmt_before_1_89_0`
+            r#"//- minicore: todo, unimplemented, fmt_before_1_89_0
 fn f() { let a: u128 = 1; let b: u128 = todo$0!("asd") }"#,
             r#"fn f() { let a: u128 = 1; let b: u128 = a }"#,
         )
@@ -110,7 +112,9 @@ fn f() { let a: u128 = 1; let b: u128 = todo$0!("asd") }"#,
     fn test_complete_unimplemented_with_msg() {
         check_assist(
             term_search,
-            r#"//- minicore: todo, unimplemented
+            // FIXME: Since we are lacking of `super let`, term search fails due to borrowck failure.
+            // Should implement super let and remove `fmt_before_1_89_0`
+            r#"//- minicore: todo, unimplemented, fmt_before_1_89_0
 fn f() { let a: u128 = 1; let b: u128 = todo$0!("asd") }"#,
             r#"fn f() { let a: u128 = 1; let b: u128 = a }"#,
         )
@@ -120,7 +124,9 @@ fn f() { let a: u128 = 1; let b: u128 = todo$0!("asd") }"#,
     fn test_complete_unimplemented() {
         check_assist(
             term_search,
-            r#"//- minicore: todo, unimplemented
+            // FIXME: Since we are lacking of `super let`, term search fails due to borrowck failure.
+            // Should implement super let and remove `fmt_before_1_89_0`
+            r#"//- minicore: todo, unimplemented, fmt_before_1_89_0
 fn f() { let a: u128 = 1; let b: u128 = todo$0!("asd") }"#,
             r#"fn f() { let a: u128 = 1; let b: u128 = a }"#,
         )
diff --git a/src/tools/rust-analyzer/crates/ide-completion/src/tests/expression.rs b/src/tools/rust-analyzer/crates/ide-completion/src/tests/expression.rs
index b46e4c32061..b2d18b796f1 100644
--- a/src/tools/rust-analyzer/crates/ide-completion/src/tests/expression.rs
+++ b/src/tools/rust-analyzer/crates/ide-completion/src/tests/expression.rs
@@ -1474,20 +1474,18 @@ fn main() {
 }
 "#,
         expect![[r#"
+            me foo()     fn(&self)
             sn box  Box::new(expr)
             sn call function(expr)
             sn const      const {}
             sn dbg      dbg!(expr)
             sn dbgr    dbg!(&expr)
             sn deref         *expr
-            sn if       if expr {}
             sn match match expr {}
-            sn not           !expr
             sn ref           &expr
             sn refm      &mut expr
             sn return  return expr
             sn unsafe    unsafe {}
-            sn while while expr {}
         "#]],
     );
 }
diff --git a/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/missing_unsafe.rs b/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/missing_unsafe.rs
index 6bd5417b25d..d8f6e813d80 100644
--- a/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/missing_unsafe.rs
+++ b/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/missing_unsafe.rs
@@ -630,6 +630,17 @@ fn main() {
         // Checks that we don't place orphan arguments for formatting under an unsafe block.
         check_diagnostics(
             r#"
+//- minicore: fmt_before_1_89_0
+fn foo() {
+    let p = 0xDEADBEEF as *const i32;
+    format_args!("", *p);
+                  // ^^ error: dereference of raw pointer is unsafe and requires an unsafe function or block
+}
+        "#,
+        );
+
+        check_diagnostics(
+            r#"
 //- minicore: fmt
 fn foo() {
     let p = 0xDEADBEEF as *const i32;
@@ -958,4 +969,18 @@ impl FooTrait for S2 {
         "#,
         );
     }
+
+    #[test]
+    fn no_false_positive_on_format_args_since_1_89_0() {
+        check_diagnostics(
+            r#"
+//- minicore: fmt
+fn test() {
+    let foo = 10;
+    let bar = true;
+    let _x = format_args!("{} {0} {} {last}", foo, bar, last = "!");
+}
+            "#,
+        );
+    }
 }
diff --git a/src/tools/rust-analyzer/crates/intern/src/symbol/symbols.rs b/src/tools/rust-analyzer/crates/intern/src/symbol/symbols.rs
index d5cbb7328c1..adc581309d1 100644
--- a/src/tools/rust-analyzer/crates/intern/src/symbol/symbols.rs
+++ b/src/tools/rust-analyzer/crates/intern/src/symbol/symbols.rs
@@ -496,6 +496,7 @@ define_symbols! {
     vectorcall,
     wasm,
     win64,
+    args,
     array,
     boxed_slice,
     completions,
diff --git a/src/tools/rust-analyzer/crates/test-utils/src/fixture.rs b/src/tools/rust-analyzer/crates/test-utils/src/fixture.rs
index 7240069753e..1d821e96e55 100644
--- a/src/tools/rust-analyzer/crates/test-utils/src/fixture.rs
+++ b/src/tools/rust-analyzer/crates/test-utils/src/fixture.rs
@@ -412,22 +412,36 @@ impl MiniCore {
         }
 
         let mut active_regions = Vec::new();
+        let mut inactive_regions = Vec::new();
         let mut seen_regions = Vec::new();
         for line in lines {
             let trimmed = line.trim();
             if let Some(region) = trimmed.strip_prefix("// region:") {
-                active_regions.push(region);
-                continue;
+                if let Some(region) = region.strip_prefix('!') {
+                    inactive_regions.push(region);
+                    continue;
+                } else {
+                    active_regions.push(region);
+                    continue;
+                }
             }
             if let Some(region) = trimmed.strip_prefix("// endregion:") {
-                let prev = active_regions.pop().unwrap();
+                let (prev, region) = if let Some(region) = region.strip_prefix('!') {
+                    (inactive_regions.pop().unwrap(), region)
+                } else {
+                    (active_regions.pop().unwrap(), region)
+                };
                 assert_eq!(prev, region, "unbalanced region pairs");
                 continue;
             }
 
-            let mut line_region = false;
-            if let Some(idx) = trimmed.find("// :") {
-                line_region = true;
+            let mut active_line_region = false;
+            let mut inactive_line_region = false;
+            if let Some(idx) = trimmed.find("// :!") {
+                inactive_line_region = true;
+                inactive_regions.push(&trimmed[idx + "// :!".len()..]);
+            } else if let Some(idx) = trimmed.find("// :") {
+                active_line_region = true;
                 active_regions.push(&trimmed[idx + "// :".len()..]);
             }
 
@@ -438,18 +452,30 @@ impl MiniCore {
                 seen_regions.push(region);
                 keep &= self.has_flag(region);
             }
+            for &region in &inactive_regions {
+                assert!(!region.starts_with(' '), "region marker starts with a space: {region:?}");
+                self.assert_valid_flag(region);
+                seen_regions.push(region);
+                keep &= !self.has_flag(region);
+            }
 
             if keep {
                 buf.push_str(line);
             }
-            if line_region {
+            if active_line_region {
                 active_regions.pop().unwrap();
             }
+            if inactive_line_region {
+                inactive_regions.pop().unwrap();
+            }
         }
 
         if !active_regions.is_empty() {
             panic!("unclosed regions: {active_regions:?} Add an `endregion` comment");
         }
+        if !inactive_regions.is_empty() {
+            panic!("unclosed regions: {inactive_regions:?} Add an `endregion` comment");
+        }
 
         for flag in &self.valid_flags {
             if !seen_regions.iter().any(|it| it == flag) {
diff --git a/src/tools/rust-analyzer/crates/test-utils/src/minicore.rs b/src/tools/rust-analyzer/crates/test-utils/src/minicore.rs
index 4bdd791eb16..d13a81d287f 100644
--- a/src/tools/rust-analyzer/crates/test-utils/src/minicore.rs
+++ b/src/tools/rust-analyzer/crates/test-utils/src/minicore.rs
@@ -31,6 +31,7 @@
 //!     eq: sized
 //!     error: fmt
 //!     fmt: option, result, transmute, coerce_unsized, copy, clone, derive
+//!     fmt_before_1_89_0: fmt
 //!     fn: tuple
 //!     from: sized, result
 //!     future: pin
@@ -1175,6 +1176,7 @@ pub mod fmt {
             }
         }
 
+        // region:fmt_before_1_89_0
         #[lang = "format_unsafe_arg"]
         pub struct UnsafeArg {
             _private: (),
@@ -1185,6 +1187,7 @@ pub mod fmt {
                 UnsafeArg { _private: () }
             }
         }
+        // endregion:fmt_before_1_89_0
     }
 
     #[derive(Copy, Clone)]
@@ -1204,6 +1207,7 @@ pub mod fmt {
             Arguments { pieces, fmt: None, args: &[] }
         }
 
+        // region:fmt_before_1_89_0
         pub fn new_v1_formatted(
             pieces: &'a [&'static str],
             args: &'a [rt::Argument<'a>],
@@ -1212,6 +1216,17 @@ pub mod fmt {
         ) -> Arguments<'a> {
             Arguments { pieces, fmt: Some(fmt), args }
         }
+        // endregion:fmt_before_1_89_0
+
+        // region:!fmt_before_1_89_0
+        pub unsafe fn new_v1_formatted(
+            pieces: &'a [&'static str],
+            args: &'a [rt::Argument<'a>],
+            fmt: &'a [rt::Placeholder],
+        ) -> Arguments<'a> {
+            Arguments { pieces, fmt: Some(fmt), args }
+        }
+        // endregion:!fmt_before_1_89_0
 
         pub const fn as_str(&self) -> Option<&'static str> {
             match (self.pieces, self.args) {