gccrs: expand: Add parser for offset_of!() and builtin resolution.

gcc/rust/ChangeLog:

	* Make-lang.in: Compile the offset_of handler.
	* lang.opt: Add -frust-assume-builtin-offset-of option.
	* ast/rust-ast.h: Add has_str() for const_TokenPtr.
	* expand/rust-macro-builtins.cc: Map offset_of as builtin.
	* expand/rust-macro-builtins.h: Declare it.
	* expand/rust-macro-expand.cc (MacroExpander::expand_invoc): Add hack for calling builtin
	offset_of!().
	* resolve/rust-early-name-resolver-2.0.cc (Early::visit):  Likewise.
	* expand/rust-macro-builtins-offset-of.cc: New file.

gcc/testsuite/ChangeLog:

	* rust/compile/offset_of1.rs: New test.

1 files changed, 4 insertions, 0 deletions

diff --git a/gcc/rust/expand/rust-macro-builtins.h b/gcc/rust/expand/rust-macro-builtins.h
index 541e956..b6c2907 100644
--- a/gcc/rust/expand/rust-macro-builtins.h
+++ b/gcc/rust/expand/rust-macro-builtins.h
@@ -19,6 +19,7 @@
 #ifndef RUST_MACRO_BUILTINS_H
 #define RUST_MACRO_BUILTINS_H
 
+#include "optional.h"
 #include "rust-ast.h"
 #include "rust-builtin-ast-nodes.h"
 #include "rust-ast-fragment.h"
@@ -188,6 +189,9 @@ public:
   format_args_handler (location_t invoc_locus, AST::MacroInvocData &invoc,
 		       AST::InvocKind semicolon, AST::FormatArgs::Newline nl);
 
+  static tl::optional<AST::Fragment>
+  offset_of_handler (location_t, AST::MacroInvocData &, AST::InvocKind);
+
   static tl::optional<AST::Fragment> sorry (location_t invoc_locus,
 					    AST::MacroInvocData &invoc,
 					    AST::InvocKind semicolon);