Stabilize Frontmatter

Author: epage

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -543,7 +543,6 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     gate_all!(contracts_internals, "contract internal machinery is for internal use only");
     gate_all!(where_clause_attrs, "attributes in `where` clause are unstable");
     gate_all!(super_let, "`super let` is experimental");
-    gate_all!(frontmatter, "frontmatters are experimental");
     gate_all!(coroutines, "coroutine syntax is experimental");
 
     if !visitor.features.never_patterns() {

compiler/rustc_feature/src/accepted.rs

@@ -227,6 +227,8 @@ declare_features! (
     (accepted, fn_must_use, "1.27.0", Some(43302)),
     /// Allows capturing variables in scope using format_args!
     (accepted, format_args_capture, "1.58.0", Some(67984)),
+    /// Frontmatter `---` blocks for use by external tools.
+    (accepted, frontmatter, "CURRENT_RUSTC_VERSION", Some(136889)),
     /// Infer generic args for both consts and types.
     (accepted, generic_arg_infer, "1.89.0", Some(85077)),
     /// Allows associated types to be generic, e.g., `type Foo<T>;` (RFC 1598).

compiler/rustc_feature/src/unstable.rs

@@ -498,8 +498,6 @@ declare_features! (
     (incomplete, fn_delegation, "1.76.0", Some(118212)),
     /// Allows impls for the Freeze trait.
     (internal, freeze_impls, "1.78.0", Some(121675)),
-    /// Frontmatter `---` blocks for use by external tools.
-    (unstable, frontmatter, "1.88.0", Some(136889)),
     /// Allows defining gen blocks and `gen fn`.
     (unstable, gen_blocks, "1.75.0", Some(117078)),
     /// Allows non-trivial generic constants which have to have wfness manually propagated to callers

compiler/rustc_parse/src/lexer/mod.rs

@@ -15,7 +15,7 @@ use rustc_session::lint::builtin::{
     TEXT_DIRECTION_CODEPOINT_IN_COMMENT, TEXT_DIRECTION_CODEPOINT_IN_LITERAL,
 };
 use rustc_session::parse::ParseSess;
-use rustc_span::{BytePos, Pos, Span, Symbol, sym};
+use rustc_span::{BytePos, Pos, Span, Symbol};
 use tracing::debug;
 
 use crate::errors;
@@ -624,7 +624,6 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
         let last_line_start_pos = frontmatter_opening_end_pos + BytePos(last_line_start as u32);
 
         let frontmatter_span = self.mk_sp(frontmatter_opening_pos, self.pos);
-        self.psess.gated_spans.gate(sym::frontmatter, frontmatter_span);
 
         if !last_line_trimmed.starts_with("---") {
             let label_span = self.mk_sp(frontmatter_opening_pos, frontmatter_opening_end_pos);

src/doc/style-guide/src/README.md

@@ -218,6 +218,38 @@ given:
 
 ### [Types](types.md)
 
+### Frontmatter
+
+There should be no blank lines between the frontmatter and either the start of the file or a shebang.
+There can be zero or one line between the frontmatter and any following content.
+
+The frontmatter fences should use the minimum number of dashes necessary for the contained content (one more than the longest series of initial dashes in the
+content, with a minimum of 3 to be recognized as frontmatter delimiters).
+If an infostring is present after the opening fence, there should be one space separating them.
+The frontmatter fence lines should not have trailing whitespace.
+
+Examples:
+
+```rust
+#!/usr/bin/env cargo
+---
+[dependencies]
+regex = "1"
+---
+
+fn main() {}
+```
+
+```rust
+#!/usr/bin/env cargo
+--- cargo
+[dependencies]
+regex = "1"
+---
+
+fn main() {}
+```
+
 ### Comments
 
 The following guidelines for comments are recommendations only, a mechanical

src/doc/style-guide/src/nightly.md

@@ -5,29 +5,3 @@ This chapter documents style and formatting for nightly-only syntax. The rest of
 Style and formatting for nightly-only syntax should be removed from this chapter and integrated into the appropriate sections of the style guide at the time of stabilization.
 
 There is no guarantee of the stability of this chapter in contrast to the rest of the style guide. Refer to the style team policy for nightly formatting procedure regarding breaking changes to this chapter.
-
-### Frontmatter
-
-*Location: Placed before comments and attributes in the [root](index.html).*
-
-*Tracking issue: [#136889](https://github.com/rust-lang/rust/issues/136889)*
-
-*Feature gate: `frontmatter`*
-
-There should be no blank lines between the frontmatter and either the start of the file or a shebang.
-There can be zero or one line between the frontmatter and any following content.
-
-The frontmatter fences should use the minimum number of dashes necessary for the contained content (one more than the longest series of initial dashes in the
-content, with a minimum of 3 to be recognized as frontmatter delimiters).
-If an infostring is present after the opening fence, there should be one space separating them.
-The frontmatter fence lines should not have trailing whitespace.
-
-```rust
-#!/usr/bin/env cargo
---- cargo
-[dependencies]
-regex = "1"
----
-
-fn main() {}
-```

src/doc/unstable-book/src/language-features/frontmatter.md

@@ -597,7 +597,7 @@ Anything to do with loops and `for`, `loop` and `while` keywords to express them
 
 ## `tests/ui/frontmatter/`
 
-Tests for `#![feature(frontmatter)]`. See [Tracking Issue for `frontmatter` #136889](https://github.com/rust-lang/rust/issues/136889).
+Tests for Cargo Script's frontmatter.
 
 ## `tests/ui/fully-qualified-type/`