[gcc/devel/rust/master] ast: Keep ConstGenericArg as default value for ConstGenericParam

[gcc/devel/rust/master] ast: Keep ConstGenericArg as default value for ConstGenericParam

[Thomas Schwinge]

https://gcc.gnu.org/g:49276efb07ef18098c0f72970acf523a1fc31eb8

commit 49276efb07ef18098c0f72970acf523a1fc31eb8
Author: Arthur Cohen <arthur.cohen@embecosm.com>
Date:   Fri Jun 24 11:54:08 2022 +0200

    ast: Keep ConstGenericArg as default value for ConstGenericParam

Diff:
---
 gcc/rust/ast/rust-ast-full-test.cc |  4 +-
 gcc/rust/ast/rust-ast.h            | 69 ----------------------------------
 gcc/rust/ast/rust-path.h           | 77 +++++++++++++++++++++++++++++++++++++-
 gcc/rust/hir/rust-ast-lower-type.h | 12 ++++--
 gcc/rust/parse/rust-parse-impl.h   |  2 +-
 5 files changed, 87 insertions(+), 77 deletions(-)

diff --git a/gcc/rust/ast/rust-ast-full-test.cc b/gcc/rust/ast/rust-ast-full-test.cc
index 81791135bc4..d98a7cfeedb 100644
--- a/gcc/rust/ast/rust-ast-full-test.cc
+++ b/gcc/rust/ast/rust-ast-full-test.cc
@@ -2365,8 +2365,8 @@ ConstGenericParam::as_string () const
   std::string str ("ConstGenericParam: ");
   str += "const " + name + ": " + type->as_string ();
 
-  if (default_value)
-    str += " = " + default_value->as_string ();
+  if (has_default_value ())
+    str += " = " + get_default_value ().as_string ();
 
   return str;
 }
diff --git a/gcc/rust/ast/rust-ast.h b/gcc/rust/ast/rust-ast.h
index 51fe3c49c59..461a2460f8f 100644
--- a/gcc/rust/ast/rust-ast.h
+++ b/gcc/rust/ast/rust-ast.h
@@ -1344,75 +1344,6 @@ protected:
   }
 };
 
-/**
- * Representation of const generic parameters
- */
-class ConstGenericParam : public GenericParam
-{
-  /* Name of the parameter */
-  Identifier name;
-
-  /* Mandatory type of the const parameter - a null pointer is an error */
-  std::unique_ptr<AST::Type> type;
-
-  /**
-   * Default value for the const generic parameter - nullptr indicates a lack
-   * of default value, not an error, as these errors are reported during
-   * parsing.
-   */
-  std::unique_ptr<AST::Expr> default_value;
-
-  Attribute outer_attr;
-  Location locus;
-
-public:
-  ConstGenericParam (Identifier name, std::unique_ptr<AST::Type> type,
-		     std::unique_ptr<AST::Expr> default_value,
-		     Attribute outer_attr, Location locus)
-    : name (name), type (std::move (type)),
-      default_value (std::move (default_value)), outer_attr (outer_attr),
-      locus (locus)
-  {}
-
-  ConstGenericParam (const ConstGenericParam &other)
-    : GenericParam (), name (other.name), type (other.type->clone_type ()),
-      outer_attr (other.outer_attr), locus (other.locus)
-  {
-    if (other.default_value)
-      default_value = other.default_value->clone_expr ();
-  }
-
-  bool has_type () { return type != nullptr; }
-  bool has_default_value () { return default_value != nullptr; }
-
-  const Identifier &get_name () const { return name; }
-
-  std::unique_ptr<AST::Type> &get_type ()
-  {
-    rust_assert (has_type ());
-
-    return type;
-  }
-
-  std::unique_ptr<AST::Expr> &get_default_value () { return default_value; }
-
-  std::string as_string () const override;
-
-  void accept_vis (ASTVisitor &vis) override;
-
-  Location get_locus () const override final { return locus; }
-
-  Kind get_kind () const override final { return Kind::Const; }
-
-protected:
-  /* Use covariance to implement clone function as returning this object rather
-   * than base */
-  ConstGenericParam *clone_generic_param_impl () const override
-  {
-    return new ConstGenericParam (*this);
-  }
-};
-
 // A macro item AST node - abstract base class
 class MacroItem : public Item
 {
diff --git a/gcc/rust/ast/rust-path.h b/gcc/rust/ast/rust-path.h
index d2d925a01ce..36f1c0478cb 100644
--- a/gcc/rust/ast/rust-path.h
+++ b/gcc/rust/ast/rust-path.h
@@ -191,7 +191,12 @@ public:
 
   Kind get_kind () const { return kind; }
 
-  std::unique_ptr<AST::Expr> &get_expression () { return expression; }
+  const std::unique_ptr<AST::Expr> &get_expression () const
+  {
+    rust_assert (kind == Kind::Clear);
+
+    return expression;
+  }
 
   std::string as_string () const
   {
@@ -241,6 +246,76 @@ private:
   Location locus;
 };
 
+/**
+ * Representation of const generic parameters
+ */
+class ConstGenericParam : public GenericParam
+{
+  /* Name of the parameter */
+  Identifier name;
+
+  /* Mandatory type of the const parameter - a null pointer is an error */
+  std::unique_ptr<AST::Type> type;
+
+  /**
+   * Default value for the const generic parameter
+   */
+  ConstGenericArg default_value;
+
+  Attribute outer_attr;
+  Location locus;
+
+public:
+  ConstGenericParam (Identifier name, std::unique_ptr<AST::Type> type,
+		     ConstGenericArg default_value, Attribute outer_attr,
+		     Location locus)
+    : name (name), type (std::move (type)),
+      default_value (std::move (default_value)), outer_attr (outer_attr),
+      locus (locus)
+  {}
+
+  ConstGenericParam (const ConstGenericParam &other)
+    : GenericParam (), name (other.name), type (other.type->clone_type ()),
+      default_value (other.default_value), outer_attr (other.outer_attr),
+      locus (other.locus)
+  {}
+
+  bool has_type () const { return type != nullptr; }
+  bool has_default_value () const { return !default_value.is_error (); }
+
+  const Identifier &get_name () const { return name; }
+
+  std::unique_ptr<AST::Type> &get_type ()
+  {
+    rust_assert (has_type ());
+
+    return type;
+  }
+
+  const ConstGenericArg &get_default_value () const
+  {
+    rust_assert (has_default_value ());
+
+    return default_value;
+  }
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  Location get_locus () const override final { return locus; }
+
+  Kind get_kind () const override final { return Kind::Const; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ConstGenericParam *clone_generic_param_impl () const override
+  {
+    return new ConstGenericParam (*this);
+  }
+};
+
 // Generic arguments allowed in each path expression segment - inline?
 struct GenericArgs
 {
diff --git a/gcc/rust/hir/rust-ast-lower-type.h b/gcc/rust/hir/rust-ast-lower-type.h
index dc20be7cd11..2bcf0ee23c4 100644
--- a/gcc/rust/hir/rust-ast-lower-type.h
+++ b/gcc/rust/hir/rust-ast-lower-type.h
@@ -376,10 +376,14 @@ public:
 				   mappings->get_next_localdef_id (crate_num));
 
     auto type = ASTLoweringType::translate (param.get_type ().get ());
-    auto default_expr
-      = param.has_default_value ()
-	  ? ASTLoweringExpr::translate (param.get_default_value ().get ())
-	  : nullptr;
+    // FIXME: Arthur: Remove the second guard once we disambiguate in the
+    // resolveer
+    HIR::Expr *default_expr = nullptr;
+    if (param.has_default_value ()
+	&& param.get_default_value ().get_kind ()
+	     == AST::ConstGenericArg::Kind::Clear)
+      default_expr = ASTLoweringExpr::translate (
+	param.get_default_value ().get_expression ().get ());
 
     translated
       = new HIR::ConstGenericParam (param.get_name (),
diff --git a/gcc/rust/parse/rust-parse-impl.h b/gcc/rust/parse/rust-parse-impl.h
index a36107b2319..6a1a3a58693 100644
--- a/gcc/rust/parse/rust-parse-impl.h
+++ b/gcc/rust/parse/rust-parse-impl.h
@@ -2901,7 +2901,7 @@ Parser<ManagedTokenSource>::parse_generic_param (EndTokenPred is_end_token)
 
 	param = std::unique_ptr<AST::ConstGenericParam> (
 	  new AST::ConstGenericParam (name_token->get_str (), std::move (type),
-				      nullptr, std::move (outer_attrs),
+				      default_expr, std::move (outer_attrs),
 				      token->get_locus ()));
 
 	break;