Merge #953

953: Refactor lang item mappings r=philberty a=philberty

This refactors how we find our lang items so that during HIR lowering
we have a generic outer attributes handler on Items. The old code only
done lang item mappings during the type check pass and assumed all
lang items are Traits which is not the case. To implement slices range
syntax actually map to structs within libcore/ops/range.rs which have
lang items on structs. This means we can have lang items on any Item.

Co-authored-by: Philip Herron <[email protected]>

Author: bors[bot]

gcc/rust/Make-lang.in

@@ -77,6 +77,7 @@ GRS_OBJS = \
     rust/rust-macro-invoc-lexer.o \
     rust/rust-hir-full-test.o \
     rust/rust-hir-map.o \
+    rust/rust-attributes.o \
     rust/rust-abi.o \
     rust/rust-ast-lower.o \
     rust/rust-ast-lower-pattern.o \

gcc/rust/hir/rust-ast-lower-base.h

@@ -24,6 +24,7 @@
 #include "rust-ast-visitor.h"
 #include "rust-hir-map.h"
 #include "rust-hir-full.h"
+#include "rust-attributes.h"
 
 namespace Rust {
 namespace HIR {
@@ -230,9 +231,13 @@ class ASTLoweringBase : public AST::ASTVisitor
   virtual void visit (AST::BareFunctionType &type) {}
 
 protected:
-  ASTLoweringBase () : mappings (Analysis::Mappings::get ()) {}
+  ASTLoweringBase ()
+    : mappings (Analysis::Mappings::get ()),
+      attr_mappings (Analysis::BuiltinAttributeMappings::get ())
+  {}
 
   Analysis::Mappings *mappings;
+  Analysis::BuiltinAttributeMappings *attr_mappings;
 
   HIR::Lifetime lower_lifetime (AST::Lifetime &lifetime)
   {
@@ -281,6 +286,16 @@ class ASTLoweringBase : public AST::ASTVisitor
 
   HIR::FunctionQualifiers
   lower_qualifiers (const AST::FunctionQualifiers &qualifiers);
+
+  void handle_outer_attributes (const HIR::Item &item);
+
+  void handle_lang_item_attribute (const HIR::Item &item,
+				   const AST::Attribute &attr);
+
+  bool is_known_attribute (const std::string &attribute_path) const;
+
+  bool
+  attribute_handled_in_another_pass (const std::string &attribute_path) const;
 };
 
 } // namespace HIR

gcc/rust/hir/rust-ast-lower-item.h

@@ -44,6 +44,10 @@ class ASTLoweringItem : public ASTLoweringBase
   {
     ASTLoweringItem resolver;
     item->accept_vis (resolver);
+
+    if (resolver.translated != nullptr)
+      resolver.handle_outer_attributes (*resolver.translated);
+
     return resolver.translated;
   }
 

gcc/rust/hir/rust-ast-lower.cc

@@ -609,5 +609,69 @@ ASTLoweringBase::lower_qualifiers (const AST::FunctionQualifiers &qualifiers)
 				  has_extern, extern_abi);
 }
 
+void
+ASTLoweringBase::handle_outer_attributes (const HIR::Item &item)
+{
+  for (const auto &attr : item.get_outer_attrs ())
+    {
+      const auto &str_path = attr.get_path ().as_string ();
+      if (!is_known_attribute (str_path))
+	{
+	  rust_error_at (attr.get_locus (), "unknown attribute");
+	  continue;
+	}
+
+      bool is_lang_item = str_path.compare ("lang") == 0
+			  && attr.has_attr_input ()
+			  && attr.get_attr_input ().get_attr_input_type ()
+			       == AST::AttrInput::AttrInputType::LITERAL;
+
+      if (is_lang_item)
+	handle_lang_item_attribute (item, attr);
+      else if (!attribute_handled_in_another_pass (str_path))
+	{
+	  rust_error_at (attr.get_locus (), "unhandled attribute: [%s]",
+			 attr.get_path ().as_string ().c_str ());
+	}
+    }
+}
+
+void
+ASTLoweringBase::handle_lang_item_attribute (const HIR::Item &item,
+					     const AST::Attribute &attr)
+{
+  auto &literal = static_cast<AST::AttrInputLiteral &> (attr.get_attr_input ());
+  const auto &lang_item_type_str = literal.get_literal ().as_string ();
+  auto lang_item_type = Analysis::RustLangItem::Parse (lang_item_type_str);
+  if (lang_item_type == Analysis::RustLangItem::ItemType::UNKNOWN)
+    {
+      rust_error_at (attr.get_locus (), "unknown lang item");
+      return;
+    }
+  mappings->insert_lang_item (lang_item_type,
+			      item.get_mappings ().get_defid ());
+}
+
+bool
+ASTLoweringBase::is_known_attribute (const std::string &attribute_path) const
+{
+  const auto &lookup = attr_mappings->lookup_builtin (attribute_path);
+  return !lookup.is_error ();
+}
+
+bool
+ASTLoweringBase::attribute_handled_in_another_pass (
+  const std::string &attribute_path) const
+{
+  const auto &lookup = attr_mappings->lookup_builtin (attribute_path);
+  if (lookup.is_error ())
+    return false;
+
+  if (lookup.handler == Analysis::CompilerPass::UNKNOWN)
+    return false;
+
+  return lookup.handler != Analysis::CompilerPass::HIR_LOWERING;
+}
+
 } // namespace HIR
 } // namespace Rust

gcc/rust/typecheck/rust-hir-trait-resolve.h

@@ -207,31 +207,6 @@ class TraitResolver : public TypeCheckBase
     // loop of trying to resolve traits as required by the types
     tref->on_resolved ();
 
-    // does this have any lang-item attributes?
-    for (auto &attr : trait_reference->get_outer_attrs ())
-      {
-	bool is_lang_item = attr.get_path ().as_string ().compare ("lang") == 0
-			    && attr.has_attr_input ()
-			    && attr.get_attr_input ().get_attr_input_type ()
-				 == AST::AttrInput::AttrInputType::LITERAL;
-	if (is_lang_item)
-	  {
-	    auto &literal
-	      = static_cast<AST::AttrInputLiteral &> (attr.get_attr_input ());
-	    const auto &lang_item_type_str
-	      = literal.get_literal ().as_string ();
-	    auto lang_item_type
-	      = Analysis::RustLangItem::Parse (lang_item_type_str);
-	    if (lang_item_type == Analysis::RustLangItem::ItemType::UNKNOWN)
-	      {
-		rust_error_at (attr.get_locus (), "unknown lang item");
-		return tref;
-	      }
-	    mappings->insert_lang_item (
-	      lang_item_type, trait_reference->get_mappings ().get_defid ());
-	  }
-      }
-
     return tref;
   }
 

gcc/rust/util/rust-attributes.cc

@@ -0,0 +1,61 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include "rust-attributes.h"
+
+namespace Rust {
+namespace Analysis {
+
+// https://doc.rust-lang.org/stable/nightly-rustc/src/rustc_feature/builtin_attrs.rs.html#256
+static const BuiltinAttrDefinition __definitions[] = {
+  {"inline", CODE_GENERATION}, {"cfg", EXPANSION},     {"cfg_attr", EXPANSION},
+  {"allow", STATIC_ANALYSIS},  {"lang", HIR_LOWERING},
+};
+
+BuiltinAttributeMappings *
+BuiltinAttributeMappings::get ()
+{
+  static BuiltinAttributeMappings *instance = nullptr;
+  if (instance == nullptr)
+    instance = new BuiltinAttributeMappings ();
+
+  return instance;
+}
+
+const BuiltinAttrDefinition &
+BuiltinAttributeMappings::lookup_builtin (const std::string &attr_name) const
+{
+  auto it = mappings.find (attr_name);
+  if (it == mappings.end ())
+    return BuiltinAttrDefinition::error_node ();
+
+  return it->second;
+}
+
+BuiltinAttributeMappings::BuiltinAttributeMappings ()
+{
+  size_t ndefinitions = sizeof (__definitions) / sizeof (BuiltinAttrDefinition);
+  for (size_t i = 0; i < ndefinitions; i++)
+    {
+      const BuiltinAttrDefinition &def = __definitions[i];
+      mappings.insert ({def.name, def});
+    }
+}
+
+} // namespace Analysis
+} // namespace Rust

gcc/rust/util/rust-attributes.h

@@ -0,0 +1,70 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include "rust-system.h"
+
+namespace Rust {
+namespace Analysis {
+
+enum CompilerPass
+{
+  UNKNOWN,
+
+  EXPANSION,
+  NAME_RESOLUTION,
+  HIR_LOWERING,
+  TYPE_CHECK,
+  STATIC_ANALYSIS,
+  CODE_GENERATION
+};
+
+struct BuiltinAttrDefinition
+{
+  std::string name;
+  CompilerPass handler;
+
+  static BuiltinAttrDefinition get_error ()
+  {
+    return BuiltinAttrDefinition{"", UNKNOWN};
+  }
+
+  static BuiltinAttrDefinition &error_node ()
+  {
+    static BuiltinAttrDefinition error_node = get_error ();
+    return error_node;
+  }
+
+  bool is_error () const { return name.empty (); }
+};
+
+class BuiltinAttributeMappings
+{
+public:
+  static BuiltinAttributeMappings *get ();
+
+  const BuiltinAttrDefinition &
+  lookup_builtin (const std::string &attr_name) const;
+
+private:
+  BuiltinAttributeMappings ();
+
+  std::map<std::string, const BuiltinAttrDefinition> mappings;
+};
+
+} // namespace Analysis
+} // namespace Rust