Remove #[main] attribute.

compiler/rustc_feature/src/active.rs

@@ -134,9 +134,6 @@ declare_features! (
     /// Allows using the `box $expr` syntax.
     (active, box_syntax, "1.0.0", Some(49733), None),
 
-    /// Allows using `#[main]` to replace the entrypoint `#[lang = "start"]` calls.
-    (active, main, "1.0.0", Some(29634), None),
-
     /// Allows using `#[start]` on a function indicating that it is the program entrypoint.
     (active, start, "1.0.0", Some(29633), None),
 

compiler/rustc_feature/src/builtin_attrs.rs

@@ -536,6 +536,10 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         rustc_specialization_trait, Normal, template!(Word),
         "the `#[rustc_specialization_trait]` attribute is used to check specializations"
     ),
+    rustc_attr!(
+        rustc_main, Normal, template!(Word),
+        "the `#[rustc_main]` attribute is used internally to specify test entry point function",
+    ),
 
     // ==========================================================================
     // Internal attributes, Testing:

compiler/rustc_feature/src/removed.rs

@@ -132,6 +132,8 @@ declare_features! (
     (removed, link_args, "1.53.0", Some(29596), None,
      Some("removed in favor of using `-C link-arg=ARG` on command line, \
            which is available from cargo build scripts with `cargo:rustc-link-arg` now")),
+    /// Allows using `#[main]` to replace the entrypoint `#[lang = "start"]` calls.
+    (removed, main, "1.53.0", Some(29634), None, None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: removed features