Rollup merge of #134140 - compiler-errors:unsafe-binders-ast, r=oli-obk

Add AST support for unsafe binders

I'm splitting up #130514 into pieces. It's impossible for me to keep up with a huge PR like that. I'll land type system support for this next, probably w/o MIR lowering, which will come later.

r? `@oli-obk`
cc `@BoxyUwU` and `@lcnr` who also may want to look at this, though this PR doesn't do too much yet

Author: matthiaskrgr

src/expr.rs

@@ -413,7 +413,8 @@ pub(crate) fn format_expr(
         ast::ExprKind::FormatArgs(..)
         | ast::ExprKind::Type(..)
         | ast::ExprKind::IncludedBytes(..)
-        | ast::ExprKind::OffsetOf(..) => {
+        | ast::ExprKind::OffsetOf(..)
+        | ast::ExprKind::UnsafeBinderCast(..) => {
             // These don't normally occur in the AST because macros aren't expanded. However,
             // rustfmt tries to parse macro arguments when formatting macros, so it's not totally
             // impossible for rustfmt to come across one of these nodes when formatting a file.

src/types.rs

@@ -1016,6 +1016,31 @@ impl Rewrite for ast::Ty {
                 let pat = pat.rewrite_result(context, shape)?;
                 Ok(format!("{ty} is {pat}"))
             }
+            ast::TyKind::UnsafeBinder(ref binder) => {
+                let mut result = String::new();
+                if let Some(ref lifetime_str) =
+                    rewrite_bound_params(context, shape, &binder.generic_params)
+                {
+                    result.push_str("unsafe<");
+                    result.push_str(lifetime_str);
+                    result.push_str("> ");
+                }
+
+                let inner_ty_shape = if context.use_block_indent() {
+                    shape
+                        .offset_left(result.len())
+                        .max_width_error(shape.width, self.span())?
+                } else {
+                    shape
+                        .visual_indent(result.len())
+                        .sub_width(result.len())
+                        .max_width_error(shape.width, self.span())?
+                };
+
+                let rewrite = binder.inner_ty.rewrite_result(context, inner_ty_shape)?;
+                result.push_str(&rewrite);
+                Ok(result)
+            }
         }
     }
 }

src/utils.rs

@@ -504,6 +504,7 @@ pub(crate) fn is_block_expr(context: &RewriteContext<'_>, expr: &ast::Expr, repr
         | ast::ExprKind::IncludedBytes(..)
         | ast::ExprKind::InlineAsm(..)
         | ast::ExprKind::OffsetOf(..)
+        | ast::ExprKind::UnsafeBinderCast(..)
         | ast::ExprKind::Let(..)
         | ast::ExprKind::Path(..)
         | ast::ExprKind::Range(..)

tests/source/unsafe-binders.rs

@@ -0,0 +1,11 @@
+fn foo() -> unsafe<'a>
+&'a () {}
+
+struct Foo {
+    x: unsafe<'a>
+&'a (),
+}
+
+struct Bar(unsafe<'a> &'a ());
+
+impl Trait for unsafe<'a> &'a () {}

tests/target/unsafe-binders.rs

@@ -0,0 +1,9 @@
+fn foo() -> unsafe<'a> &'a () {}
+
+struct Foo {
+    x: unsafe<'a> &'a (),
+}
+
+struct Bar(unsafe<'a> &'a ());
+
+impl Trait for unsafe<'a> &'a () {}