Revert "Stabilize C string literals"

This reverts commit 0f41bc2.

Author: wesleywiser

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -515,6 +515,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
             }
         };
     }
+    gate_all!(c_str_literals, "`c\"..\"` literals are experimental");
     gate_all!(
         if_let_guard,
         "`if let` guards are experimental",

compiler/rustc_builtin_macros/src/concat_bytes.rs

@@ -19,8 +19,8 @@ fn invalid_type_err(
     let snippet = cx.sess.source_map().span_to_snippet(span).ok();
     match ast::LitKind::from_token_lit(token_lit) {
         Ok(ast::LitKind::CStr(_, _)) => {
-            // Avoid ambiguity in handling of terminal `NUL` by refusing to
-            // concatenate C string literals as bytes.
+            // FIXME(c_str_literals): should concatenation of C string literals
+            // include the null bytes in the end?
             cx.emit_err(errors::ConcatCStrLit { span: span });
         }
         Ok(ast::LitKind::Char(_)) => {

compiler/rustc_feature/src/accepted.rs

@@ -76,8 +76,6 @@ declare_features! (
     (accepted, bindings_after_at, "1.56.0", Some(65490)),
     /// Allows empty structs and enum variants with braces.
     (accepted, braced_empty_structs, "1.8.0", Some(29720)),
-    /// Allows `c"foo"` literals.
-    (accepted, c_str_literals, "1.76.0", Some(105723)),
     /// Allows `#[cfg_attr(predicate, multiple, attributes, here)]`.
     (accepted, cfg_attr_multi, "1.33.0", Some(54881)),
     /// Allows the use of `#[cfg(doctest)]`, set when rustdoc is collecting doctests.

compiler/rustc_feature/src/unstable.rs

@@ -359,6 +359,8 @@ declare_features! (
     (unstable, async_fn_track_caller, "1.73.0", Some(110011)),
     /// Allows builtin # foo() syntax
     (unstable, builtin_syntax, "1.71.0", Some(110680)),
+    /// Allows `c"foo"` literals.
+    (unstable, c_str_literals, "1.71.0", Some(105723)),
     /// Treat `extern "C"` function as nounwind.
     (unstable, c_unwind, "1.52.0", Some(74990)),
     /// Allows using C-variadics.

compiler/rustc_parse/src/lexer/mod.rs

@@ -223,6 +223,9 @@ impl<'a> StringReader<'a> {
                 rustc_lexer::TokenKind::Literal { kind, suffix_start } => {
                     let suffix_start = start + BytePos(suffix_start);
                     let (kind, symbol) = self.cook_lexer_literal(start, suffix_start, kind);
+                    if let token::LitKind::CStr | token::LitKind::CStrRaw(_) = kind {
+                        self.sess.gated_spans.gate(sym::c_str_literals, self.mk_sp(start, self.pos));
+                    }
                     let suffix = if suffix_start < self.pos {
                         let string = self.str_from(suffix_start);
                         if string == "_" {

src/tools/clippy/tests/ui/needless_raw_string.fixed

@@ -1,5 +1,6 @@
 #![allow(clippy::needless_raw_string_hashes, clippy::no_effect, unused)]
 #![warn(clippy::needless_raw_strings)]
+#![feature(c_str_literals)]
 
 fn main() {
     "aaa";

src/tools/clippy/tests/ui/needless_raw_string.rs

@@ -1,5 +1,6 @@
 #![allow(clippy::needless_raw_string_hashes, clippy::no_effect, unused)]
 #![warn(clippy::needless_raw_strings)]
+#![feature(c_str_literals)]
 
 fn main() {
     r#"aaa"#;

src/tools/clippy/tests/ui/needless_raw_string.stderr

@@ -1,5 +1,5 @@
 error: unnecessary raw string literal
-  --> $DIR/needless_raw_string.rs:5:5
+  --> $DIR/needless_raw_string.rs:6:5
    |
 LL |     r#"aaa"#;
    |     ^^^^^^^^
@@ -13,7 +13,7 @@ LL +     "aaa";
    |
 
 error: unnecessary raw string literal
-  --> $DIR/needless_raw_string.rs:8:5
+  --> $DIR/needless_raw_string.rs:9:5
    |
 LL |     br#"aaa"#;
    |     ^^^^^^^^^
@@ -25,7 +25,7 @@ LL +     b"aaa";
    |
 
 error: unnecessary raw string literal
-  --> $DIR/needless_raw_string.rs:11:5
+  --> $DIR/needless_raw_string.rs:12:5
    |
 LL |     cr#"aaa"#;
    |     ^^^^^^^^^
@@ -37,7 +37,7 @@ LL +     c"aaa";
    |
 
 error: unnecessary raw string literal
-  --> $DIR/needless_raw_string.rs:15:5
+  --> $DIR/needless_raw_string.rs:16:5
    |
 LL | /     r#"
 LL | |         a
@@ -56,7 +56,7 @@ LL ~     ";
    |
 
 error: unnecessary raw string literal
-  --> $DIR/needless_raw_string.rs:21:5
+  --> $DIR/needless_raw_string.rs:22:5
    |
 LL |     r"no hashes";
    |     ^^^^^^^^^^^^
@@ -68,7 +68,7 @@ LL +     "no hashes";
    |
 
 error: unnecessary raw string literal
-  --> $DIR/needless_raw_string.rs:22:5
+  --> $DIR/needless_raw_string.rs:23:5
    |
 LL |     br"no hashes";
    |     ^^^^^^^^^^^^^
@@ -80,7 +80,7 @@ LL +     b"no hashes";
    |
 
 error: unnecessary raw string literal
-  --> $DIR/needless_raw_string.rs:23:5
+  --> $DIR/needless_raw_string.rs:24:5
    |
 LL |     cr"no hashes";
    |     ^^^^^^^^^^^^^

src/tools/clippy/tests/ui/needless_raw_string_hashes.fixed

@@ -1,5 +1,6 @@
 #![allow(clippy::no_effect, unused)]
 #![warn(clippy::needless_raw_string_hashes)]
+#![feature(c_str_literals)]
 
 fn main() {
     r"\aaa";

src/tools/clippy/tests/ui/needless_raw_string_hashes.rs

@@ -1,5 +1,6 @@
 #![allow(clippy::no_effect, unused)]
 #![warn(clippy::needless_raw_string_hashes)]
+#![feature(c_str_literals)]
 
 fn main() {
     r#"\aaa"#;