Auto merge of #66671 - matthewjasper:ast-address-of, r=Centril

Ast address-of

This is the parts of #64588 that don't affect MIR. If an address-of expression makes it to MIR lowering we error and lower to the best currently expressible approximation to limit further errors.

r? @Centril

6 files changed, 45 insertions, 23 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 14243076941..dc26929100a 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -754,6 +754,21 @@ impl Mutability {
     }
 }
 
+/// The kind of borrow in an `AddrOf` expression,
+/// e.g., `&place` or `&raw const place`.
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(RustcEncodable, RustcDecodable, HashStable_Generic)]
+pub enum BorrowKind {
+    /// A raw borrow, `&raw const $expr` or `&raw mut $expr`.
+    /// The resulting type is either `*const T` or `*mut T`
+    /// where `T = typeof($expr)`.
+    Ref,
+    /// A normal borrow, `&$expr` or `&mut $expr`.
+    /// The resulting type is either `&'a T` or `&'a mut T`
+    /// where `T = typeof($expr)` and `'a` is some lifetime.
+    Raw,
+}
+
 #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug, Copy)]
 pub enum BinOpKind {
     /// The `+` operator (addition)
@@ -1071,7 +1086,7 @@ impl Expr {
 
             ExprKind::Paren(expr) => expr.to_ty().map(TyKind::Paren)?,
 
-            ExprKind::AddrOf(mutbl, expr) => expr
+            ExprKind::AddrOf(BorrowKind::Ref, mutbl, expr) => expr
                 .to_ty()
                 .map(|ty| TyKind::Rptr(None, MutTy { ty, mutbl: *mutbl }))?,
 
@@ -1262,8 +1277,8 @@ pub enum ExprKind {
     /// Optionally "qualified" (e.g., `<Vec<T> as SomeTrait>::SomeType`).
     Path(Option<QSelf>, Path),
 
-    /// A referencing operation (`&a` or `&mut a`).
-    AddrOf(Mutability, P<Expr>),
+    /// A referencing operation (`&a`, `&mut a`, `&raw const a` or `&raw mut a`).
+    AddrOf(BorrowKind, Mutability, P<Expr>),
     /// A `break`, with an optional label to break, and an optional expression.
     Break(Option<Label>, Option<P<Expr>>),
     /// A `continue`, with an optional label.
diff --git a/src/libsyntax/feature_gate/active.rs b/src/libsyntax/feature_gate/active.rs
index fa0ab90c702..b04b30aa6bc 100644
--- a/src/libsyntax/feature_gate/active.rs
+++ b/src/libsyntax/feature_gate/active.rs
@@ -520,13 +520,16 @@ declare_features! (
     /// Allows using the `efiapi` ABI.
     (active, abi_efiapi, "1.40.0", Some(65815), None),
 
+    /// Allows `&raw const $place_expr` and `&raw mut $place_expr` expressions.
+    (active, raw_ref_op, "1.41.0", Some(64490), None),
+
     /// Allows diverging expressions to fall back to `!` rather than `()`.
     (active, never_type_fallback, "1.41.0", Some(65992), None),
 
     /// Allows using the `#[register_attr]` attribute.
     (active, register_attr, "1.41.0", Some(66080), None),
 
-    /// Allows using the `#[register_attr]` attribute.
+    /// Allows using the `#[register_tool]` attribute.
     (active, register_tool, "1.41.0", Some(66079), None),
 
     /// Allows the use of `if` and `match` in constants.
diff --git a/src/libsyntax/feature_gate/check.rs b/src/libsyntax/feature_gate/check.rs
index f966850254f..846508bd0cd 100644
--- a/src/libsyntax/feature_gate/check.rs
+++ b/src/libsyntax/feature_gate/check.rs
@@ -866,6 +866,7 @@ pub fn check_crate(krate: &ast::Crate,
     gate_all!(generators, "yield syntax is experimental");
     gate_all!(or_patterns, "or-patterns syntax is experimental");
     gate_all!(const_extern_fn, "`const extern fn` definitions are unstable");
+    gate_all!(raw_ref_op, "raw address of syntax is experimental");
 
     // All uses of `gate_all!` below this point were added in #65742,
     // and subsequently disabled (with the non-early gating readded).
diff --git a/src/libsyntax/mut_visit.rs b/src/libsyntax/mut_visit.rs
index a7bd587ac9b..fbe28215a56 100644
--- a/src/libsyntax/mut_visit.rs
+++ b/src/libsyntax/mut_visit.rs
@@ -1128,7 +1128,7 @@ pub fn noop_visit_expr<T: MutVisitor>(Expr { kind, id, span, attrs }: &mut Expr,
             vis.visit_expr(expr);
             vis.visit_ty(ty);
         }
-        ExprKind::AddrOf(_m, ohs) => vis.visit_expr(ohs),
+        ExprKind::AddrOf(_, _, ohs) => vis.visit_expr(ohs),
         ExprKind::Let(pat, scrutinee) => {
             vis.visit_pat(pat);
             vis.visit_expr(scrutinee);
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 17a7cbddff9..0d2e8dddce6 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -984,16 +984,12 @@ impl<'a> State<'a> {
             }
             ast::TyKind::Ptr(ref mt) => {
                 self.s.word("*");
-                match mt.mutbl {
-                    ast::Mutability::Mutable => self.word_nbsp("mut"),
-                    ast::Mutability::Immutable => self.word_nbsp("const"),
-                }
-                self.print_type(&mt.ty);
+                self.print_mt(mt, true);
             }
             ast::TyKind::Rptr(ref lifetime, ref mt) => {
                 self.s.word("&");
                 self.print_opt_lifetime(lifetime);
-                self.print_mt(mt);
+                self.print_mt(mt, false);
             }
             ast::TyKind::Never => {
                 self.s.word("!");
@@ -1974,10 +1970,17 @@ impl<'a> State<'a> {
     }
 
     fn print_expr_addr_of(&mut self,
+                          kind: ast::BorrowKind,
                           mutability: ast::Mutability,
                           expr: &ast::Expr) {
         self.s.word("&");
-        self.print_mutability(mutability);
+        match kind {
+            ast::BorrowKind::Ref => self.print_mutability(mutability, false),
+            ast::BorrowKind::Raw => {
+                self.word_nbsp("raw");
+                self.print_mutability(mutability, true);
+            }
+        }
         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
     }
 
@@ -2028,8 +2031,8 @@ impl<'a> State<'a> {
             ast::ExprKind::Unary(op, ref expr) => {
                 self.print_expr_unary(op, expr);
             }
-            ast::ExprKind::AddrOf(m, ref expr) => {
-                self.print_expr_addr_of(m, expr);
+            ast::ExprKind::AddrOf(k, m, ref expr) => {
+                self.print_expr_addr_of(k, m, expr);
             }
             ast::ExprKind::Lit(ref lit) => {
                 self.print_literal(lit);
@@ -2361,7 +2364,7 @@ impl<'a> State<'a> {
                 match binding_mode {
                     ast::BindingMode::ByRef(mutbl) => {
                         self.word_nbsp("ref");
-                        self.print_mutability(mutbl);
+                        self.print_mutability(mutbl, false);
                     }
                     ast::BindingMode::ByValue(ast::Mutability::Immutable) => {}
                     ast::BindingMode::ByValue(ast::Mutability::Mutable) => {
@@ -2504,17 +2507,17 @@ impl<'a> State<'a> {
     fn print_explicit_self(&mut self, explicit_self: &ast::ExplicitSelf) {
         match explicit_self.node {
             SelfKind::Value(m) => {
-                self.print_mutability(m);
+                self.print_mutability(m, false);
                 self.s.word("self")
             }
             SelfKind::Region(ref lt, m) => {
                 self.s.word("&");
                 self.print_opt_lifetime(lt);
-                self.print_mutability(m);
+                self.print_mutability(m, false);
                 self.s.word("self")
             }
             SelfKind::Explicit(ref typ, m) => {
-                self.print_mutability(m);
+                self.print_mutability(m, false);
                 self.s.word("self");
                 self.word_space(":");
                 self.print_type(typ)
@@ -2746,15 +2749,15 @@ impl<'a> State<'a> {
         }
     }
 
-    pub fn print_mutability(&mut self, mutbl: ast::Mutability) {
+    pub fn print_mutability(&mut self, mutbl: ast::Mutability, print_const: bool) {
         match mutbl {
             ast::Mutability::Mutable => self.word_nbsp("mut"),
-            ast::Mutability::Immutable => {},
+            ast::Mutability::Immutable => if print_const { self.word_nbsp("const"); },
         }
     }
 
-    crate fn print_mt(&mut self, mt: &ast::MutTy) {
-        self.print_mutability(mt.mutbl);
+    crate fn print_mt(&mut self, mt: &ast::MutTy, print_const: bool) {
+        self.print_mutability(mt.mutbl, print_const);
         self.print_type(&mt.ty)
     }
 
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index f7b06c55a3a..5ff337fb60e 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -708,7 +708,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
             visitor.visit_expr(left_expression);
             visitor.visit_expr(right_expression)
         }
-        ExprKind::AddrOf(_, ref subexpression) | ExprKind::Unary(_, ref subexpression) => {
+        ExprKind::AddrOf(_, _, ref subexpression) | ExprKind::Unary(_, ref subexpression) => {
             visitor.visit_expr(subexpression)
         }
         ExprKind::Cast(ref subexpression, ref typ) | ExprKind::Type(ref subexpression, ref typ) => {