gccrs: Correctly emit warning on invalid attributes

We were emitting warning even on attribute that were then removed by
the cfgstrip pass. We cannot move the cfg strip pass before the attribute
checking because we need to first emit malformed input error messages.
This means the attribute checking pass must know if an attribute input
may be removed later down the line.

gcc/rust/ChangeLog:

	* ast/rust-ast.cc (MetaItemPathExpr::to_attribute): Remove cast to
	literal.
	(AttrInputMetaItemContainer::separate_cfg_attrs): Remove PathExpr
	specific code.
	* expand/rust-cfg-strip.cc (expand_cfg_attrs): Remove the whole
	attribute if condition's result is false.
	* util/rust-attributes.cc (AttributeChecker::visit): Remove specific
	code section for meta item container. Do not check input if
	configuration does not match condition.

gcc/testsuite/ChangeLog:

	* rust/compile/attr_malformed_path.rs: Filter existing test to x86_64
	exclusively, add two new tests that appear when visiting the resulting
	expression.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

gcc/rust/ast/rust-ast.cc

@@ -4200,10 +4200,8 @@ MetaListNameValueStr::to_attribute () const
 Attribute
 MetaItemPathExpr::to_attribute () const
 {
-  rust_assert (expr->is_literal ());
-  auto &lit = static_cast<LiteralExpr &> (*expr);
-  return Attribute (path, std::unique_ptr<AttrInputLiteral> (
-			    new AttrInputLiteral (lit)));
+  auto input = std::make_unique<AttrInputExpr> (expr->clone_expr ());
+  return Attribute (path, std::move (input));
 }
 
 std::vector<Attribute>
@@ -4219,13 +4217,9 @@ AttrInputMetaItemContainer::separate_cfg_attrs () const
 
   for (auto it = items.begin () + 1; it != items.end (); ++it)
     {
-      if ((*it)->get_kind () == MetaItemInner::Kind::MetaItem
-	  && static_cast<MetaItem &> (**it).get_item_kind ()
-	       == MetaItem::ItemKind::PathExpr
-	  && !static_cast<MetaItemPathExpr &> (**it).get_expr ().is_literal ())
-	continue;
+      auto &item = **it;
 
-      Attribute attr = (*it)->to_attribute ();
+      Attribute attr = item.to_attribute ();
       if (attr.is_empty ())
 	{
 	  /* TODO should this be an error that causes us to chuck out

gcc/rust/expand/rust-cfg-strip.cc

@@ -93,6 +93,9 @@ expand_cfg_attrs (AST::AttrVec &attrs)
 
 	  if (attr.check_cfg_predicate (session))
 	    {
+	      // Key has been found we need to remove the conditional part of
+	      // the attribute and insert the content back
+
 	      // split off cfg_attr
 	      AST::AttrVec new_attrs = attr.separate_cfg_attrs ();
 
@@ -110,6 +113,12 @@ expand_cfg_attrs (AST::AttrVec &attrs)
 	       */
 	      i--;
 	    }
+	  else
+	    {
+	      // Key has not been found, remove the whole attribute
+	      attrs.erase (attrs.begin () + i);
+	      i--;
+	    }
 
 	  /* do something - if feature (first token in tree) is in fact enabled,
 	   * make tokens listed afterwards into attributes. i.e.: for

gcc/rust/util/rust-attributes.cc

@@ -553,34 +553,28 @@ check_lint_attribute (const AST::Attribute &attribute, const char *name)
 void
 AttributeChecker::visit (AST::Attribute &attribute)
 {
-  if (!attribute.empty_input ())
+  auto &session = Session::get_instance ();
+  if (attribute.get_path () == Values::Attributes::CFG_ATTR)
     {
-      const auto &attr_input = attribute.get_attr_input ();
-      auto type = attr_input.get_attr_input_type ();
-      if (type == AST::AttrInput::AttrInputType::TOKEN_TREE)
-	{
-	  const auto &option = static_cast<const AST::DelimTokenTree &> (
-	    attribute.get_attr_input ());
-	  std::unique_ptr<AST::AttrInputMetaItemContainer> meta_item (
-	    option.parse_to_meta_item ());
-	  AST::DefaultASTVisitor::visit (meta_item);
-	}
+      if (!attribute.is_parsed_to_meta_item ())
+	attribute.parse_attr_to_meta_item ();
+      if (!attribute.check_cfg_predicate (session))
+	return; // Do not emit errors for attribute that'll get stripped.
     }
 
-  auto result_opt = identify_builtin (attribute);
+  if (auto builtin = identify_builtin (attribute))
+    {
+      auto result = builtin.value ();
+      // TODO: Add checks here for each builtin attribute
+      // TODO: Have an enum of builtins as well, switching on strings is
+      // annoying and costly
+      if (result.name == Attrs::DOC)
+	check_doc_attribute (attribute);
+      else if (result.name == Attrs::DEPRECATED)
+	check_deprecated_attribute (attribute);
+    }
 
-  // This checker does not check non-builtin attributes
-  if (!result_opt.has_value ())
-    return;
-  auto result = result_opt.value ();
-
-  // TODO: Add checks here for each builtin attribute
-  // TODO: Have an enum of builtins as well, switching on strings is annoying
-  // and costly
-  if (result.name == Attrs::DOC)
-    check_doc_attribute (attribute);
-  else if (result.name == Attrs::DEPRECATED)
-    check_deprecated_attribute (attribute);
+  AST::DefaultASTVisitor::visit (attribute);
 }
 
 void

gcc/testsuite/rust/compile/attr_malformed_path.rs

@@ -3,4 +3,6 @@
 
 #[cfg_attr(target_arch = "x86_64", path = (target_arch = "x86",    path = "x86.rs"))]
 mod imp {}
-// { dg-error "malformed .path. attribute input" "" { target *-*-* } .-2 }
+// { dg-error "malformed .path. attribute input" "" { target { x86_64-*-* && { lp64 } } } .-2 }
+// { dg-error "cannot find value .target_arch. in this scope" "" { target { x86_64-*-* && { lp64 } } } .-3 }
+// { dg-error "cannot find value .path. in this scope" "" { target { x86_64-*-* && { lp64 } } } .-4 }