Add option_env! support

gcc/rust/ChangeLog:
	* ast/rust-collect-lang-items.cc: Allow for the collection of
	EnumItem lang-items
	* ast/rust-collect-lang-items.h: ...
	* ast/rust-path.h: Add simplified method for checking if a path
	refers to a lang-item
	* expand/rust-macro-builtins-utility.cc: Add macro expansion for
	option_env with eager expansion
	* expand/rust-macro-builtins.cc: Add option_env to builtin list
	* expand/rust-macro-builtins.h: Add option_env handler to header
	file
	* ast/rust-ast-visitor.cc: Prevent AST passes from attempting to
	recurse into lang-item path's segments.
	* expand/rust-cfg-strip.cc: ...
	* resolve/rust-early-name-resolver.cc: ...
	* expand/rust-expand-visitor.cc: ...
	* hir/tree/rust-hir-path.h: Refactor
	HIR::PathInExpression to allow for lang items.
	* hir/tree/rust-hir-path.cc: ...
	* hir/rust-ast-lower.cc: Add hir translation for lang-item
	PathInExpressions.
	* resolve/rust-ast-resolve-path.cc: Add NR1.0 resolution support
	for lang-item paths.
	* typecheck/rust-hir-type-check-path.cc: Add type resolution
	support for lang-item paths.
	* typecheck/rust-hir-type-check-expr.h: Add prototype
	for helper function.
	* backend/rust-compile-resolve-path.cc: Add compile support for
	lang-item paths.
	* checks/lints/rust-lint-marklive.cc: Add if guard to prevent
	recursion into a lang-item path's empty segments.

gcc/testsuite/ChangeLog:
	* rust/compile/macros/builtin/option_env1.rs: Add success case for option_env
	* rust/compile/macros/builtin/option_env2.rs: Add failure case for option_env
	* rust/execute/torture/builtin_macro_option_env.rs: Add
	execution case for option_env
	* rust/compile/nr2/exclude: Some issues with nr2 need to be
	resolved before allowing option_env with NR2.0.

Signed-off-by: Liam Naddell <[email protected]>

gcc/rust/ast/rust-ast-visitor.cc

@@ -89,6 +89,12 @@ void
 DefaultASTVisitor::visit (AST::PathInExpression &path)
 {
   visit_outer_attrs (path);
+
+  // Do not recurse into the segments of a lang-item path, since these paths
+  // have no segments.
+  if (path.is_lang_item ())
+    return;
+
   for (auto &segment : path.get_segments ())
     visit (segment);
 }

gcc/rust/ast/rust-collect-lang-items.cc

@@ -64,7 +64,7 @@ template <typename T>
 void
 CollectLangItems::maybe_add_lang_item (const T &item)
 {
-  if (auto lang_item = get_lang_item_attr (item))
+  if (tl::optional<LangItem::Kind> lang_item = get_lang_item_attr (item))
     mappings.insert_lang_item_node (lang_item.value (), item.get_node_id ());
 }
 
@@ -100,5 +100,13 @@ CollectLangItems::visit (AST::StructStruct &item)
   DefaultASTVisitor::visit (item);
 }
 
+void
+CollectLangItems::visit (AST::EnumItem &item)
+{
+  maybe_add_lang_item (item);
+
+  DefaultASTVisitor::visit (item);
+}
+
 } // namespace AST
 } // namespace Rust

gcc/rust/ast/rust-collect-lang-items.h

@@ -49,6 +49,7 @@ class CollectLangItems : public DefaultASTVisitor
   void visit (AST::TraitItemType &item) override;
   void visit (AST::Function &item) override;
   void visit (AST::StructStruct &item) override;
+  void visit (AST::EnumItem &item) override;
 
 private:
   template <typename T> void maybe_add_lang_item (const T &item);

gcc/rust/ast/rust-path.h

@@ -622,7 +622,6 @@ class Path : public Pattern
 
   std::string as_string () const override;
 
-  // TODO: this seems kinda dodgy
   std::vector<PathExprSegment> &get_segments ()
   {
     rust_assert (kind == Kind::Regular);
@@ -643,6 +642,8 @@ class Path : public Pattern
   Pattern::Kind get_pattern_kind () override { return Pattern::Kind::Path; }
   Path::Kind get_path_kind () { return kind; }
 
+  bool is_lang_item () { return get_path_kind () == Kind::LangItem; }
+
 protected:
   std::vector<PathExprSegment> segments;
   tl::optional<LangItem::Kind> lang_item;

gcc/rust/backend/rust-compile-resolve-path.cc

@@ -42,8 +42,26 @@ ResolvePathRef::visit (HIR::QualifiedPathInExpression &expr)
 void
 ResolvePathRef::visit (HIR::PathInExpression &expr)
 {
-  resolved = resolve (expr.get_final_segment ().get_segment (),
-		      expr.get_mappings (), expr.get_locus (), false);
+  if (expr.is_lang_item ())
+    {
+      // FIXME: Currently this is written to handle lang-item paths which point
+      // to enum variants. If lang-item PathInExpression's refer to other types,
+      // this might need rewriting.
+      TyTy::BaseType *lookup = nullptr;
+      bool ok
+	= ctx->get_tyctx ()->lookup_type (expr.get_mappings ().get_hirid (),
+					  &lookup);
+      rust_assert (ok);
+
+      tree t = attempt_constructor_expression_lookup (lookup, ctx,
+						      expr.get_mappings (),
+						      expr.get_locus ());
+      TREE_USED (t) = 1;
+      resolved = t;
+    }
+  else
+    resolved = resolve (expr.get_final_segment ().get_segment (),
+			expr.get_mappings (), expr.get_locus (), false);
 }
 
 tree

gcc/rust/checks/lints/rust-lint-marklive.cc

@@ -99,9 +99,10 @@ MarkLive::visit (HIR::PathInExpression &expr)
 {
   // We should iterate every path segment in order to mark the struct which
   // is used in expression like Foo::bar(), we should mark the Foo alive.
-  expr.iterate_path_segments ([&] (HIR::PathExprSegment &seg) -> bool {
-    return visit_path_segment (seg);
-  });
+  if (!expr.is_lang_item ())
+    expr.iterate_path_segments ([&] (HIR::PathExprSegment &seg) -> bool {
+      return visit_path_segment (seg);
+    });
 
   // after iterate the path segments, we should mark functions and associated
   // functions alive.

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

@@ -434,6 +434,9 @@ CfgStrip::visit (AST::PathInExpression &path)
       return;
     }
 
+  if (path.is_lang_item ())
+    return;
+
   for (auto &segment : path.get_segments ())
     {
       if (segment.has_generic_args ())

gcc/rust/expand/rust-expand-visitor.cc

@@ -477,6 +477,9 @@ ExpandVisitor::visit (AST::MacroInvocation &macro_invoc)
 void
 ExpandVisitor::visit (AST::PathInExpression &path)
 {
+  if (path.is_lang_item ())
+    return;
+
   for (auto &segment : path.get_segments ())
     if (segment.has_generic_args ())
       expand_generic_args (segment.get_generic_args ());

gcc/rust/expand/rust-macro-builtins-utility.cc

@@ -17,6 +17,7 @@
 // <http://www.gnu.org/licenses/>.
 
 #include "rust-fmt.h"
+#include "rust-ast-builder.h"
 #include "rust-macro-builtins.h"
 #include "rust-macro-builtins-helpers.h"
 
@@ -226,6 +227,83 @@ MacroBuiltin::env_handler (location_t invoc_locus, AST::MacroInvocData &invoc,
   return AST::Fragment ({node}, std::move (tok));
 }
 
+/* Expand builtin macro option_env!(), which inspects an environment variable at
+   compile time. */
+tl::optional<AST::Fragment>
+MacroBuiltin::option_env_handler (location_t invoc_locus,
+				  AST::MacroInvocData &invoc,
+				  AST::InvocKind semicolon)
+{
+  auto invoc_token_tree = invoc.get_delim_tok_tree ();
+  MacroInvocLexer lex (invoc_token_tree.to_token_stream ());
+  Parser<MacroInvocLexer> parser (lex);
+
+  auto last_token_id = macro_end_token (invoc_token_tree, parser);
+  std::unique_ptr<AST::LiteralExpr> lit_expr = nullptr;
+  bool has_error = false;
+
+  auto start = lex.get_offs ();
+  auto expanded_expr = try_expand_many_expr (parser, last_token_id,
+					     invoc.get_expander (), has_error);
+  auto end = lex.get_offs ();
+
+  auto tokens = lex.get_token_slice (start, end);
+
+  if (has_error)
+    return AST::Fragment::create_error ();
+
+  auto pending = check_for_eager_invocations (expanded_expr);
+  if (!pending.empty ())
+    return make_eager_builtin_invocation (BuiltinMacro::OptionEnv, invoc_locus,
+					  invoc_token_tree,
+					  std::move (pending));
+
+  if (expanded_expr.size () != 1)
+    {
+      rust_error_at (invoc_locus, "%<option_env!%> takes 1 argument");
+      return AST::Fragment::create_error ();
+    }
+
+  if (expanded_expr.size () > 0)
+    if (!(lit_expr
+	  = try_extract_string_literal_from_fragment (invoc_locus,
+						      expanded_expr[0])))
+      return AST::Fragment::create_error ();
+
+  parser.skip_token (last_token_id);
+
+  auto env_value = getenv (lit_expr->as_string ().c_str ());
+  AST::Builder b (invoc_locus);
+
+  if (env_value == nullptr)
+    {
+      auto none_expr = std::unique_ptr<AST::Expr> (
+	new AST::PathInExpression (LangItem::Kind::OPTION_NONE, {},
+				   invoc_locus));
+
+      auto node = AST::SingleASTNode (std::move (none_expr));
+      std::vector<AST::SingleASTNode> nodes;
+      nodes.push_back (node);
+
+      return AST::Fragment (nodes, std::vector<std::unique_ptr<AST::Token>> ());
+    }
+  std::vector<std::unique_ptr<AST::Expr>> args;
+  args.push_back (b.literal_string (env_value));
+
+  std::unique_ptr<AST::Expr> some_expr
+    = b.call (std::unique_ptr<AST::Expr> (
+		new AST::PathInExpression (LangItem::Kind::OPTION_SOME, {},
+					   invoc_locus)),
+	      std::move (args));
+
+  auto node = AST::SingleASTNode (std::move (some_expr));
+
+  std::vector<AST::SingleASTNode> nodes;
+  nodes.push_back (node);
+
+  return AST::Fragment (nodes, std::vector<std::unique_ptr<AST::Token>> ());
+}
+
 tl::optional<AST::Fragment>
 MacroBuiltin::cfg_handler (location_t invoc_locus, AST::MacroInvocData &invoc,
 			   AST::InvocKind semicolon)

gcc/rust/expand/rust-macro-builtins.cc

@@ -120,8 +120,8 @@ std::unordered_map<std::string, AST::MacroTranscriberFunc>
     {"format_args_nl", format_args_maker (AST::FormatArgs::Newline::Yes)},
     {"asm", inline_asm_maker (AST::AsmKind::Inline)},
     {"global_asm", inline_asm_maker (AST::AsmKind::Global)},
+    {"option_env", MacroBuiltin::option_env_handler},
     /* Unimplemented macro builtins */
-    {"option_env", MacroBuiltin::sorry},
     {"concat_idents", MacroBuiltin::sorry},
     {"module_path", MacroBuiltin::sorry},
     {"log_syntax", MacroBuiltin::sorry},

gcc/rust/expand/rust-macro-builtins.h

@@ -159,6 +159,10 @@ class MacroBuiltin
 						  AST::MacroInvocData &invoc,
 						  AST::InvocKind semicolon);
 
+  static tl::optional<AST::Fragment>
+  option_env_handler (location_t invoc_locus, AST::MacroInvocData &invoc,
+		      AST::InvocKind semicolon);
+
   static tl::optional<AST::Fragment> cfg_handler (location_t invoc_locus,
 						  AST::MacroInvocData &invoc,
 						  AST::InvocKind semicolon);

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

@@ -495,6 +495,17 @@ void
 ASTLowerPathInExpression::visit (AST::PathInExpression &expr)
 {
   std::vector<HIR::PathExprSegment> path_segments;
+  auto crate_num = mappings.get_current_crate ();
+  Analysis::NodeMapping mapping (crate_num, expr.get_node_id (),
+				 mappings.get_next_hir_id (crate_num),
+				 UNKNOWN_LOCAL_DEFID);
+  if (expr.get_path_kind () == AST::Path::Kind::LangItem)
+    {
+      translated = new HIR::PathInExpression (mapping, expr.get_lang_item (),
+					      expr.get_locus (),
+					      expr.opening_scope_resolution ());
+      return;
+    }
   auto &segments = expr.get_segments ();
   for (auto &s : segments)
     {
@@ -504,10 +515,6 @@ ASTLowerPathInExpression::visit (AST::PathInExpression &expr)
       HIR::PathExprSegment *lowered_seg = &path_segments.back ();
       mappings.insert_hir_path_expr_seg (lowered_seg);
     }
-  auto crate_num = mappings.get_current_crate ();
-  Analysis::NodeMapping mapping (crate_num, expr.get_node_id (),
-				 mappings.get_next_hir_id (crate_num),
-				 UNKNOWN_LOCAL_DEFID);
 
   translated = new HIR::PathInExpression (mapping, std::move (path_segments),
 					  expr.get_locus (),

gcc/rust/hir/tree/rust-hir-path.cc

@@ -133,13 +133,15 @@ PathExprSegment::operator= (PathExprSegment const &other)
 void
 PathPattern::iterate_path_segments (std::function<bool (PathExprSegment &)> cb)
 {
+  rust_assert (!is_lang_item ());
   for (auto it = segments.begin (); it != segments.end (); it++)
     {
       if (!cb (*it))
 	return;
     }
 }
 
+// Path constructor
 PathInExpression::PathInExpression (Analysis::NodeMapping mappings,
 				    std::vector<PathExprSegment> path_segments,
 				    location_t locus,
@@ -150,6 +152,16 @@ PathInExpression::PathInExpression (Analysis::NodeMapping mappings,
     has_opening_scope_resolution (has_opening_scope_resolution), locus (locus)
 {}
 
+// Lang-item constructor.
+PathInExpression::PathInExpression (Analysis::NodeMapping mappings,
+				    LangItem::Kind lang_item, location_t locus,
+				    bool has_opening_scope_resolution,
+				    std::vector<AST::Attribute> outer_attrs)
+  : PathPattern (lang_item),
+    PathExpr (std::move (mappings), std::move (outer_attrs)),
+    has_opening_scope_resolution (has_opening_scope_resolution), locus (locus)
+{}
+
 bool
 PathInExpression::is_self () const