Stabilize Frontmatter

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -524,7 +524,6 @@ 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

@@ -223,6 +223,8 @@ 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

@@ -518,8 +518,6 @@ 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;
@@ -626,7 +626,6 @@ 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() {}
-```

tests/ui/README.md

@@ -613,7 +613,7 @@ 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/`
 

tests/ui/frontmatter/content-contains-whitespace.rs

@@ -17,6 +17,4 @@ package.description = """
 
 // Ensure the frontmatter can contain any whitespace
 
-#![feature(frontmatter)]
-
 fn main() {}

tests/ui/frontmatter/content-non-lexible-tokens.rs

@@ -4,8 +4,6 @@
 
 //@ check-pass
 
-#![feature(frontmatter)]
-
 // check that frontmatter blocks can have tokens that are otherwise not accepted by
 // the lexer as Rust code.
 

tests/ui/frontmatter/escape-hyphens-leading.rs

@@ -9,6 +9,4 @@
 // This test checks that longer dashes for opening and closing can be used to
 // escape sequences such as three dashes inside the frontmatter block.
 
-#![feature(frontmatter)]
-
 fn main() {}

tests/ui/frontmatter/escape-hyphens-nonleading-1.rs

@@ -7,6 +7,4 @@
 // hyphens only need to be escaped when at the start of a line
 //@ check-pass
 
-#![feature(frontmatter)]
-
 fn main() {}

tests/ui/frontmatter/escape-hyphens-nonleading-2.rs

@@ -5,6 +5,4 @@ x ---🚧️
 // Regression test for #141483
 //@check-pass
 
-#![feature(frontmatter)]
-
 fn main() {}

tests/ui/frontmatter/escape-hyphens-nonleading-3.rs

@@ -6,6 +6,4 @@ x ---y
 // non-whitespace character preceding them.
 //@check-pass
 
-#![feature(frontmatter)]
-
 fn main() {}

tests/ui/frontmatter/fence-close-extra-after.rs

@@ -2,6 +2,4 @@
 ---cargo
 //~^ ERROR: extra characters after frontmatter close are not allowed
 
-#![feature(frontmatter)]
-
 fn main() {}

tests/ui/frontmatter/fence-indented-mismatch.rs

@@ -1,14 +1,13 @@
 ---cargo
-//~^ ERROR: unclosed frontmatter
 
 //@ compile-flags: --crate-type lib
 
-#![feature(frontmatter)]
-
 fn foo(x: i32) -> i32 {
     ---x
-     //~^ WARNING: use of a double negation [double_negations]
+     //~^ ERROR invalid preceding whitespace for frontmatter close
+     //~^^ ERROR extra characters after frontmatter close are not allowed
 }
+//~^ ERROR unexpected closing delimiter: `}`
 
 // this test is for the weird case that valid Rust code can have three dashes
 // within them and get treated as a frontmatter close.

tests/ui/frontmatter/fence-indented-mismatch.stderr

@@ -1,30 +1,26 @@
-error: unclosed frontmatter
-  --> $DIR/fence-indented-mismatch.rs:1:1
+error: invalid preceding whitespace for frontmatter close
+  --> $DIR/fence-indented-mismatch.rs:6:1
    |
-LL | / ---cargo
-...  |
-LL | |
-   | |_^
+LL |     ---x
+   | ^^^^^^^^
    |
-note: frontmatter opening here was not closed
-  --> $DIR/fence-indented-mismatch.rs:1:1
+note: frontmatter close should not be preceded by whitespace
+  --> $DIR/fence-indented-mismatch.rs:6:1
    |
-LL | ---cargo
-   | ^^^
+LL |     ---x
+   | ^^^^
 
-warning: use of a double negation
-  --> $DIR/fence-indented-mismatch.rs:9:6
+error: extra characters after frontmatter close are not allowed
+  --> $DIR/fence-indented-mismatch.rs:6:1
    |
 LL |     ---x
-   |      ^^^
-   |
-   = note: the prefix `--` could be misinterpreted as a decrement operator which exists in other languages
-   = note: use `-= 1` if you meant to decrement the value
-   = note: `#[warn(double_negations)]` on by default
-help: add parentheses for clarity
+   | ^^^^^^^^
+
+error: unexpected closing delimiter: `}`
+  --> $DIR/fence-indented-mismatch.rs:9:1
    |
-LL |     --(-x)
-   |       +  +
+LL | }
+   | ^ unexpected closing delimiter
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 3 previous errors
 

tests/ui/frontmatter/fence-indented.rs

@@ -1,9 +1,7 @@
   ---
 //~^ ERROR: invalid preceding whitespace for frontmatter opening
-//~^^ ERROR: unclosed frontmatter
   ---
-
-#![feature(frontmatter)]
+//~^ ERROR: invalid preceding whitespace for frontmatter close
 
 // check that whitespaces should not precede the frontmatter opening or close.
 

tests/ui/frontmatter/fence-indented.stderr

@@ -10,21 +10,17 @@ note: frontmatter opening should not be preceded by whitespace
 LL |   ---
    | ^^
 
-error: unclosed frontmatter
-  --> $DIR/fence-indented.rs:1:3
+error: invalid preceding whitespace for frontmatter close
+  --> $DIR/fence-indented.rs:3:1
    |
-LL | /   ---
-LL | |
-LL | |
-LL | |   ---
-LL | |
-   | |_^
+LL |   ---
+   | ^^^^^
    |
-note: frontmatter opening here was not closed
-  --> $DIR/fence-indented.rs:1:3
+note: frontmatter close should not be preceded by whitespace
+  --> $DIR/fence-indented.rs:3:1
    |
 LL |   ---
-   |   ^^^
+   | ^^
 
 error: aborting due to 2 previous errors
 

tests/ui/frontmatter/fence-mismatch-1.rs

@@ -5,6 +5,4 @@
 // there must be the same number of dashes for both the opening and the close
 // of the frontmatter.
 
-#![feature(frontmatter)]
-
 fn main() {}

tests/ui/frontmatter/fence-mismatch-2.rs

@@ -3,6 +3,4 @@
 ---cargo
 //~^ ERROR: extra characters after frontmatter close are not allowed
 
-#![feature(frontmatter)]
-
 fn main() {}

tests/ui/frontmatter/fence-unclosed-1.rs

@@ -5,6 +5,5 @@
 // close. There should not be a "missing `main` function" error as the rest
 // are properly parsed.
 
-#![feature(frontmatter)]
-
+//~v ERROR: `main` function not found in crate `fence_unclosed_1`
 fn main() {}

tests/ui/frontmatter/fence-unclosed-1.stderr

@@ -3,14 +3,21 @@ error: unclosed frontmatter
    |
 LL | / ----cargo
 ...  |
-LL | |
-   | |_^
+LL | | fn main() {}
+   | |_____________^
    |
 note: frontmatter opening here was not closed
   --> $DIR/fence-unclosed-1.rs:1:1
    |
 LL | ----cargo
    | ^^^^
 
-error: aborting due to 1 previous error
+error[E0601]: `main` function not found in crate `fence_unclosed_1`
+  --> $DIR/fence-unclosed-1.rs:9:14
+   |
+LL | fn main() {}
+   |             ^ consider adding a `main` function to `$DIR/fence-unclosed-1.rs`
+
+error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0601`.

tests/ui/frontmatter/fence-unclosed-2.rs

@@ -1,15 +1,12 @@
 ----cargo
 //~^ ERROR: unclosed frontmatter
-//~| ERROR: frontmatters are experimental
 
 //@ compile-flags: --crate-type lib
 
 // Leading whitespace on the feature line prevents recovery. However
 // the dashes quoted will not be used for recovery and the entire file
 // should be treated as within the frontmatter block.
 
- #![feature(frontmatter)]
-
 fn foo() -> &str {
     "----"
 }