Auto merge of #61995 - eddyb:hir-sep-ptr, r=petrochenkov

rustc: use a separate copy of P for HIR than for AST.

Note: this currently includes/is based on top of #61987.

Like #61968, but goes one step further and uses a separate `P<...>` for the HIR, with no `Clone`, or the ability to mutate after allocation.
There is still `into_inner`/`into_iter`, but they're only exposed for `hir::lowering`, and they would take more work to untangle.

r? @petrochenkov cc @rust-lang/compiler

2 files changed, 3 insertions, 2 deletions

diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 337b8424736..1fe3dfa40ee 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -12,6 +12,7 @@
 #![deny(unused_lifetimes)]
 
 #![feature(bind_by_move_pattern_guards)]
+#![feature(box_syntax)]
 #![feature(const_fn)]
 #![feature(const_transmute)]
 #![feature(crate_visibility_modifier)]
diff --git a/src/libsyntax/ptr.rs b/src/libsyntax/ptr.rs
index f0cfa5a84a8..be580dc2e6a 100644
--- a/src/libsyntax/ptr.rs
+++ b/src/libsyntax/ptr.rs
@@ -41,11 +41,11 @@ pub struct P<T: ?Sized> {
     ptr: Box<T>
 }
 
-#[allow(non_snake_case)]
 /// Construct a `P<T>` from a `T` value.
+#[allow(non_snake_case)]
 pub fn P<T: 'static>(value: T) -> P<T> {
     P {
-        ptr: Box::new(value)
+        ptr: box value
     }
 }