gccrs: Desugar double borrows into two HIR:BorrowExpr's

We simply hit a gcc_unreachable() on double borrows but it seems reasonable
to just desugar the AST into a borrow of a borrow to foo. Instead of a
borrow expression with a flag to be respected.

Fixes #1506

gcc/rust/ChangeLog:

	* hir/rust-ast-lower-expr.h: Lower double borrow expressions to two
	`HIR::BorrowExpr`s.
	* hir/tree/rust-hir-expr.h: Remove `is_double_borrow` field from
	`HIR::BorrowExpr`.
	* typecheck/rust-hir-type-check-expr.cc (TypeCheckExpr::visit): Remove
	call to `gcc_unreachable` on double borrow expressions.

gcc/testsuite/ChangeLog:

	* rust/compile/torture/issue-1506.rs: New test.

diff --git a/gcc/rust/hir/rust-ast-lower-expr.h b/gcc/rust/hir/rust-ast-lower-expr.h
index 92773b6..b0ab409 100644 (file)
--- a/gcc/rust/hir/rust-ast-lower-expr.h
+++ b/gcc/rust/hir/rust-ast-lower-expr.h
@@ -643,10 +643,29 @@ public:
                                   mappings->get_next_hir_id (crate_num),
                                   UNKNOWN_LOCAL_DEFID);
 
-    translated = new HIR::BorrowExpr (
-      mapping, std::unique_ptr<HIR::Expr> (borrow_lvalue),
-      expr.get_is_mut () ? Mutability::Mut : Mutability::Imm,
-      expr.get_is_double_borrow (), expr.get_outer_attrs (), expr.get_locus ());
+    HIR::BorrowExpr *borrow_expr
+      = new HIR::BorrowExpr (mapping,
+                            std::unique_ptr<HIR::Expr> (borrow_lvalue),
+                            expr.get_is_mut () ? Mutability::Mut
+                                               : Mutability::Imm,
+                            expr.get_outer_attrs (), expr.get_locus ());
+
+    if (expr.get_is_double_borrow ())
+      {
+       NodeId artifical_bouble_borrow_id = mappings->get_next_node_id ();
+       Analysis::NodeMapping mapping (crate_num, artifical_bouble_borrow_id,
+                                      mappings->get_next_hir_id (crate_num),
+                                      UNKNOWN_LOCAL_DEFID);
+
+       borrow_expr
+         = new HIR::BorrowExpr (mapping,
+                                std::unique_ptr<HIR::Expr> (borrow_expr),
+                                expr.get_is_mut () ? Mutability::Mut
+                                                   : Mutability::Imm,
+                                expr.get_outer_attrs (), expr.get_locus ());
+      }
+
+    translated = borrow_expr;
   }
 
   void visit (AST::DereferenceExpr &expr) override

diff --git a/gcc/rust/hir/tree/rust-hir-expr.h b/gcc/rust/hir/tree/rust-hir-expr.h
index 5a1e976..564d521 100644 (file)
--- a/gcc/rust/hir/tree/rust-hir-expr.h
+++ b/gcc/rust/hir/tree/rust-hir-expr.h
@@ -192,10 +192,10 @@ public:
 
   BorrowExpr (Analysis::NodeMapping mappings,
              std::unique_ptr<Expr> borrow_lvalue, Mutability mut,
-             bool is_double_borrow, AST::AttrVec outer_attribs, Location locus)
+             AST::AttrVec outer_attribs, Location locus)
     : OperatorExpr (std::move (mappings), std::move (borrow_lvalue),
                    std::move (outer_attribs), locus),
-      mut (mut), double_borrow (is_double_borrow)
+      mut (mut)
   {}
 
   void accept_vis (HIRFullVisitor &vis) override;
@@ -203,7 +203,6 @@ public:
 
   Mutability get_mut () const { return mut; }
   bool is_mut () const { return mut == Mutability::Mut; }
-  bool get_is_double_borrow () const { return double_borrow; }
 
 protected:
   /* Use covariance to implement clone function as returning this object rather

diff --git a/gcc/rust/typecheck/rust-hir-type-check-expr.cc b/gcc/rust/typecheck/rust-hir-type-check-expr.cc
index 41c8cd1..c415ae9 100644 (file)
--- a/gcc/rust/typecheck/rust-hir-type-check-expr.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-expr.cc
@@ -1209,12 +1209,6 @@ TypeCheckExpr::visit (HIR::BorrowExpr &expr)
        }
     }
 
-  if (expr.get_is_double_borrow ())
-    {
-      // FIXME double_reference
-      gcc_unreachable ();
-    }
-
   infered = new TyTy::ReferenceType (expr.get_mappings ().get_hirid (),
                                     TyTy::TyVar (resolved_base->get_ref ()),
                                     expr.get_mut ());

diff --git a/gcc/testsuite/rust/compile/torture/issue-1506.rs b/gcc/testsuite/rust/compile/torture/issue-1506.rs
new file mode 100644 (file)
index 0000000..a38f231
--- /dev/null
+++ b/gcc/testsuite/rust/compile/torture/issue-1506.rs
@@ -0,0 +1,3 @@
+pub fn main() {
+    let _: &i32 = &&&&1;
+}