Rollup merge of #130635 - eholk:pin-reborrow-sugar, r=compiler-errors

Add `&pin (mut|const) T` type position sugar

This adds parser support for `&pin mut T` and `&pin const T` references. These are desugared to `Pin<&mut T>` and `Pin<&T>` in the AST lowering phases.

This PR currently includes #130526 since that one is in the commit queue. Only the most recent commits (bd450027eb4a94b814a7dd9c0fa29102e6361149 and following) are new.

Tracking:

- #130494

r? `@compiler-errors`

Author: matthiaskrgr

src/types.rs

@@ -827,7 +827,8 @@ impl Rewrite for ast::Ty {
 
                 rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
             }
-            ast::TyKind::Ref(ref lifetime, ref mt) => {
+            ast::TyKind::Ref(ref lifetime, ref mt)
+            | ast::TyKind::PinnedRef(ref lifetime, ref mt) => {
                 let mut_str = format_mutability(mt.mutbl);
                 let mut_len = mut_str.len();
                 let mut result = String::with_capacity(128);
@@ -861,6 +862,13 @@ impl Rewrite for ast::Ty {
                     cmnt_lo = lifetime.ident.span.hi();
                 }
 
+                if let ast::TyKind::PinnedRef(..) = self.kind {
+                    result.push_str("pin ");
+                    if ast::Mutability::Not == mt.mutbl {
+                        result.push_str("const ");
+                    }
+                }
+
                 if ast::Mutability::Mut == mt.mutbl {
                     let mut_hi = context.snippet_provider.span_after(self.span(), "mut");
                     let before_mut_span = mk_sp(cmnt_lo, mut_hi - BytePos::from_usize(3));
@@ -1260,9 +1268,9 @@ pub(crate) fn can_be_overflowed_type(
 ) -> bool {
     match ty.kind {
         ast::TyKind::Tup(..) => context.use_block_indent() && len == 1,
-        ast::TyKind::Ref(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
-            can_be_overflowed_type(context, &*mutty.ty, len)
-        }
+        ast::TyKind::Ref(_, ref mutty)
+        | ast::TyKind::PinnedRef(_, ref mutty)
+        | ast::TyKind::Ptr(ref mutty) => can_be_overflowed_type(context, &*mutty.ty, len),
         _ => false,
     }
 }

tests/source/pin_sugar.rs

@@ -0,0 +1,10 @@
+// See #130494
+
+#![feature(pin_ergonomics)]
+#![allow(incomplete_features)]
+
+fn f(x: &pin  const i32) {}
+fn g<'a>(x: &  'a pin const  i32) {}
+fn h<'a>(x: &  'a pin  
+mut i32) {}
+fn i(x: &pin      mut  i32) {}

tests/target/pin_sugar.rs

@@ -0,0 +1,9 @@
+// See #130494
+
+#![feature(pin_ergonomics)]
+#![allow(incomplete_features)]
+
+fn f(x: &pin const i32) {}
+fn g<'a>(x: &'a pin const i32) {}
+fn h<'a>(x: &'a pin mut i32) {}
+fn i(x: &pin mut i32) {}