Merge #1336

1336: Resolve const generic parameters r=CohenArthur a=CohenArthur

Fixes #1319.

This can only resolve the simpler test cases: Anything that is ambiguous is ignored and does not get resolved. This will be fixed very soon :)

Co-authored-by: Arthur Cohen <arthur.cohen@embecosm.com>

10 files changed, 154 insertions, 171 deletions

diff --git a/gcc/rust/ast/rust-ast-full-test.cc b/gcc/rust/ast/rust-ast-full-test.cc
index 8179113..d98a7cf 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 51fe3c4..461a246 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 d2d925a..36f1c04 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 dc20be7..2bcf0ee 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 a36107b..6a1a3a5 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;
diff --git a/gcc/rust/resolve/rust-ast-resolve-item.cc b/gcc/rust/resolve/rust-ast-resolve-item.cc
index 1ad91af..62518b6 100644
--- a/gcc/rust/resolve/rust-ast-resolve-item.cc
+++ b/gcc/rust/resolve/rust-ast-resolve-item.cc
@@ -73,10 +73,8 @@ ResolveTraitItems::visit (AST::TraitItemFunc &func)
 
   AST::TraitFunctionDecl &function = func.get_trait_function_decl ();
   if (function.has_generics ())
-    {
-      for (auto &generic : function.get_generic_params ())
-	ResolveGenericParam::go (generic.get ());
-    }
+    for (auto &generic : function.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   if (function.has_return_type ())
     ResolveType::go (function.get_return_type ().get ());
@@ -122,10 +120,8 @@ ResolveTraitItems::visit (AST::TraitItemMethod &func)
 
   AST::TraitMethodDecl &function = func.get_trait_method_decl ();
   if (function.has_generics ())
-    {
-      for (auto &generic : function.get_generic_params ())
-	ResolveGenericParam::go (generic.get ());
-    }
+    for (auto &generic : function.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   if (function.has_return_type ())
     ResolveType::go (function.get_return_type ().get ());
@@ -210,10 +206,8 @@ ResolveItem::visit (AST::TypeAlias &alias)
   resolver->get_type_scope ().push (scope_node_id);
 
   if (alias.has_generics ())
-    {
-      for (auto &generic : alias.get_generic_params ())
-	ResolveGenericParam::go (generic.get ());
-    }
+    for (auto &generic : alias.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   if (alias.has_where_clause ())
     ResolveWhereClause::Resolve (alias.get_where_clause ());
@@ -274,12 +268,8 @@ ResolveItem::visit (AST::TupleStruct &struct_decl)
   resolver->get_type_scope ().push (scope_node_id);
 
   if (struct_decl.has_generics ())
-    {
-      for (auto &generic : struct_decl.get_generic_params ())
-	{
-	  ResolveGenericParam::go (generic.get ());
-	}
-    }
+    for (auto &generic : struct_decl.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   if (struct_decl.has_where_clause ())
     ResolveWhereClause::Resolve (struct_decl.get_where_clause ());
@@ -313,12 +303,8 @@ ResolveItem::visit (AST::Enum &enum_decl)
   resolver->get_type_scope ().push (scope_node_id);
 
   if (enum_decl.has_generics ())
-    {
-      for (auto &generic : enum_decl.get_generic_params ())
-	{
-	  ResolveGenericParam::go (generic.get ());
-	}
-    }
+    for (auto &generic : enum_decl.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, cpath);
 
   if (enum_decl.has_where_clause ())
     ResolveWhereClause::Resolve (enum_decl.get_where_clause ());
@@ -411,12 +397,8 @@ ResolveItem::visit (AST::StructStruct &struct_decl)
   resolver->get_type_scope ().push (scope_node_id);
 
   if (struct_decl.has_generics ())
-    {
-      for (auto &generic : struct_decl.get_generic_params ())
-	{
-	  ResolveGenericParam::go (generic.get ());
-	}
-    }
+    for (auto &generic : struct_decl.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   if (struct_decl.has_where_clause ())
     ResolveWhereClause::Resolve (struct_decl.get_where_clause ());
@@ -450,12 +432,8 @@ ResolveItem::visit (AST::Union &union_decl)
   resolver->get_type_scope ().push (scope_node_id);
 
   if (union_decl.has_generics ())
-    {
-      for (auto &generic : union_decl.get_generic_params ())
-	{
-	  ResolveGenericParam::go (generic.get ());
-	}
-    }
+    for (auto &generic : union_decl.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   if (union_decl.has_where_clause ())
     ResolveWhereClause::Resolve (union_decl.get_where_clause ());
@@ -523,10 +501,8 @@ ResolveItem::visit (AST::Function &function)
   resolver->push_new_label_rib (resolver->get_type_scope ().peek ());
 
   if (function.has_generics ())
-    {
-      for (auto &generic : function.get_generic_params ())
-	ResolveGenericParam::go (generic.get ());
-    }
+    for (auto &generic : function.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   // resolve any where clause items
   if (function.has_where_clause ())
@@ -566,12 +542,8 @@ ResolveItem::visit (AST::InherentImpl &impl_block)
   resolve_visibility (impl_block.get_visibility ());
 
   if (impl_block.has_generics ())
-    {
-      for (auto &generic : impl_block.get_generic_params ())
-	{
-	  ResolveGenericParam::go (generic.get ());
-	}
-    }
+    for (auto &generic : impl_block.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   // resolve any where clause items
   if (impl_block.has_where_clause ())
@@ -657,10 +629,8 @@ ResolveItem::visit (AST::Method &method)
   resolver->push_new_label_rib (resolver->get_type_scope ().peek ());
 
   if (method.has_generics ())
-    {
-      for (auto &generic : method.get_generic_params ())
-	ResolveGenericParam::go (generic.get ());
-    }
+    for (auto &generic : method.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   // resolve any where clause items
   if (method.has_where_clause ())
@@ -719,12 +689,8 @@ ResolveItem::visit (AST::TraitImpl &impl_block)
   resolver->push_new_type_rib (resolver->get_type_scope ().peek ());
 
   if (impl_block.has_generics ())
-    {
-      for (auto &generic : impl_block.get_generic_params ())
-	{
-	  ResolveGenericParam::go (generic.get ());
-	}
-    }
+    for (auto &generic : impl_block.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   // resolve any where clause items
   if (impl_block.has_where_clause ())
@@ -836,9 +802,7 @@ ResolveItem::visit (AST::Trait &trait)
   CanonicalPath Self = CanonicalPath::get_big_self (trait.get_node_id ());
 
   for (auto &generic : trait.get_generic_params ())
-    {
-      ResolveGenericParam::go (generic.get ());
-    }
+    ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   // Self is an implicit TypeParam so lets mark it as such
   resolver->get_type_scope ().append_reference_for_def (
@@ -900,7 +864,7 @@ ResolveItem::resolve_impl_item (AST::InherentImplItem *item,
 void
 ResolveItem::resolve_extern_item (AST::ExternalItem *item)
 {
-  ResolveExternItem::go (item);
+  ResolveExternItem::go (item, prefix, canonical_prefix);
 }
 
 static void
@@ -1070,9 +1034,10 @@ ResolveImplItems::visit (AST::TypeAlias &alias)
 }
 
 void
-ResolveExternItem::go (AST::ExternalItem *item)
+ResolveExternItem::go (AST::ExternalItem *item, const CanonicalPath &prefix,
+		       const CanonicalPath &canonical_prefix)
 {
-  ResolveExternItem resolver;
+  ResolveExternItem resolver (prefix, canonical_prefix);
   item->accept_vis (resolver);
 }
 
@@ -1092,10 +1057,8 @@ ResolveExternItem::visit (AST::ExternalFunctionItem &function)
 
   // resolve the generics
   if (function.has_generics ())
-    {
-      for (auto &generic : function.get_generic_params ())
-	ResolveGenericParam::go (generic.get ());
-    }
+    for (auto &generic : function.get_generic_params ())
+      ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
   if (function.has_return_type ())
     ResolveType::go (function.get_return_type ().get ());
diff --git a/gcc/rust/resolve/rust-ast-resolve-item.h b/gcc/rust/resolve/rust-ast-resolve-item.h
index 2824d09..ce521f0 100644
--- a/gcc/rust/resolve/rust-ast-resolve-item.h
+++ b/gcc/rust/resolve/rust-ast-resolve-item.h
@@ -118,13 +118,20 @@ class ResolveExternItem : public ResolverBase
   using Rust::Resolver::ResolverBase::visit;
 
 public:
-  static void go (AST::ExternalItem *item);
+  static void go (AST::ExternalItem *item, const CanonicalPath &prefix,
+		  const CanonicalPath &canonical_prefix);
 
   void visit (AST::ExternalFunctionItem &function) override;
   void visit (AST::ExternalStaticItem &item) override;
 
 private:
-  ResolveExternItem () : ResolverBase () {}
+  ResolveExternItem (const CanonicalPath &prefix,
+		     const CanonicalPath &canonical_prefix)
+    : ResolverBase (), prefix (prefix), canonical_prefix (canonical_prefix)
+  {}
+
+  const CanonicalPath &prefix;
+  const CanonicalPath &canonical_prefix;
 };
 
 } // namespace Resolver
diff --git a/gcc/rust/resolve/rust-ast-resolve-stmt.cc b/gcc/rust/resolve/rust-ast-resolve-stmt.cc
index 6fc929f..1ce3df0 100644
--- a/gcc/rust/resolve/rust-ast-resolve-stmt.cc
+++ b/gcc/rust/resolve/rust-ast-resolve-stmt.cc
@@ -30,7 +30,7 @@ ResolveStmt::visit (AST::ExternBlock &extern_block)
     {
       ResolveToplevelExternItem::go (item.get (),
 				     CanonicalPath::create_empty ());
-      ResolveExternItem::go (item.get ());
+      ResolveExternItem::go (item.get (), prefix, canonical_prefix);
     }
 }
 
diff --git a/gcc/rust/resolve/rust-ast-resolve-stmt.h b/gcc/rust/resolve/rust-ast-resolve-stmt.h
index 202a280..8867845 100644
--- a/gcc/rust/resolve/rust-ast-resolve-stmt.h
+++ b/gcc/rust/resolve/rust-ast-resolve-stmt.h
@@ -111,9 +111,7 @@ public:
     if (struct_decl.has_generics ())
       {
 	for (auto &generic : struct_decl.get_generic_params ())
-	  {
-	    ResolveGenericParam::go (generic.get ());
-	  }
+	  ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
       }
 
     for (AST::TupleField &field : struct_decl.get_fields ())
@@ -145,9 +143,7 @@ public:
     if (enum_decl.has_generics ())
       {
 	for (auto &generic : enum_decl.get_generic_params ())
-	  {
-	    ResolveGenericParam::go (generic.get ());
-	  }
+	  ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
       }
 
     for (auto &variant : enum_decl.get_variants ())
@@ -271,9 +267,7 @@ public:
     if (struct_decl.has_generics ())
       {
 	for (auto &generic : struct_decl.get_generic_params ())
-	  {
-	    ResolveGenericParam::go (generic.get ());
-	  }
+	  ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
       }
 
     for (AST::StructField &field : struct_decl.get_fields ())
@@ -308,12 +302,8 @@ public:
     resolver->get_type_scope ().push (scope_node_id);
 
     if (union_decl.has_generics ())
-      {
-	for (auto &generic : union_decl.get_generic_params ())
-	  {
-	    ResolveGenericParam::go (generic.get ());
-	  }
-      }
+      for (auto &generic : union_decl.get_generic_params ())
+	ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
     for (AST::StructField &field : union_decl.get_variants ())
       {
@@ -352,10 +342,8 @@ public:
     resolver->push_new_label_rib (resolver->get_type_scope ().peek ());
 
     if (function.has_generics ())
-      {
-	for (auto &generic : function.get_generic_params ())
-	  ResolveGenericParam::go (generic.get ());
-      }
+      for (auto &generic : function.get_generic_params ())
+	ResolveGenericParam::go (generic.get (), prefix, canonical_prefix);
 
     if (function.has_return_type ())
       ResolveType::go (function.get_return_type ().get ());
diff --git a/gcc/rust/resolve/rust-ast-resolve-type.h b/gcc/rust/resolve/rust-ast-resolve-type.h
index 965df42..946cdd4 100644
--- a/gcc/rust/resolve/rust-ast-resolve-type.h
+++ b/gcc/rust/resolve/rust-ast-resolve-type.h
@@ -20,6 +20,7 @@
 #define RUST_AST_RESOLVE_TYPE_H
 
 #include "rust-ast-resolve-base.h"
+#include "rust-ast-resolve-expr.h"
 #include "rust-ast-full.h"
 
 namespace Rust {
@@ -146,17 +147,23 @@ class ResolveGenericParam : public ResolverBase
   using Rust::Resolver::ResolverBase::visit;
 
 public:
-  static NodeId go (AST::GenericParam *param)
+  static NodeId go (AST::GenericParam *param, const CanonicalPath &prefix,
+		    const CanonicalPath &canonical_prefix)
   {
-    ResolveGenericParam resolver;
+    ResolveGenericParam resolver (prefix, canonical_prefix);
     param->accept_vis (resolver);
     return resolver.resolved_node;
   }
 
-  void visit (AST::ConstGenericParam &) override
+  void visit (AST::ConstGenericParam &param) override
   {
-    // For now do not do anything and accept everything.
-    // FIXME: This needs to change soon!
+    ResolveType::go (param.get_type ().get ());
+
+    if (param.has_default_value ())
+      ResolveExpr::go (param.get_default_value ().get_expression ().get (),
+		       prefix, canonical_prefix);
+
+    ok = true;
   }
 
   void visit (AST::TypeParam &param) override
@@ -188,7 +195,15 @@ public:
   }
 
 private:
-  ResolveGenericParam () : ResolverBase () {}
+  ResolveGenericParam (const CanonicalPath &prefix,
+		       const CanonicalPath &canonical_prefix)
+    : ResolverBase (), ok (false), prefix (prefix),
+      canonical_prefix (canonical_prefix)
+  {}
+
+  bool ok;
+  const CanonicalPath &prefix;
+  const CanonicalPath &canonical_prefix;
 };
 
 class ResolveWhereClause : public ResolverBase