lexer: Allow specifiying tokens as reserved in certain editions

Some tokens such as `try` only became reserved keywords in certain
editions. This behavior might happen again in the future and we should
be able to handle it.

4 files changed, 33 insertions, 4 deletions

diff --git a/gcc/rust/lex/rust-lex.cc b/gcc/rust/lex/rust-lex.cc
index 93d96d3..ecf151d 100644
--- a/gcc/rust/lex/rust-lex.cc
+++ b/gcc/rust/lex/rust-lex.cc
@@ -21,6 +21,7 @@
 #include "rust-system.h"      // for rust_assert and rust_unreachable
 #include "rust-diagnostics.h" // for rust_error_at
 #include "rust-linemap.h"
+#include "rust-session-manager.h"
 #include "safe-ctype.h"
 
 namespace Rust {
@@ -228,10 +229,24 @@ Lexer::classify_keyword (const std::string &str)
 
   if (idx == last || str != *idx)
     return IDENTIFIER;
-  else
-    return keyword_keys[idx - keyword_index];
 
   // TODO: possibly replace this x-macro system with something like hash map?
+
+  // We now have the expected token ID of the reserved keyword. However, some
+  // keywords are reserved starting in certain editions. For example, `try` is
+  // only a reserved keyword in editions >=2018. The language might gain new
+  // reserved keywords in the future.
+  //
+  // https://doc.rust-lang.org/reference/keywords.html#reserved-keywords
+  auto id = keyword_keys[idx - keyword_index];
+
+  // `try` is not a reserved keyword before 2018
+  if (Session::get_instance ().options.get_edition ()
+	== CompileOptions::Edition::E2015
+      && id == TRY)
+    return IDENTIFIER;
+
+  return id;
 }
 
 TokenPtr
diff --git a/gcc/rust/rust-session-manager.h b/gcc/rust/rust-session-manager.h
index c68e796..24a15f5 100644
--- a/gcc/rust/rust-session-manager.h
+++ b/gcc/rust/rust-session-manager.h
@@ -191,13 +191,13 @@ struct CompileOptions
   bool proc_macro = false;
   std::string metadata_output_path;
 
-  enum Edition
+  enum class Edition
   {
     E2015 = 0,
     E2018,
     E2021,
   } edition
-    = E2015;
+    = Edition::E2015;
 
   bool dump_option_enabled (DumpOption option) const
   {
@@ -239,6 +239,8 @@ struct CompileOptions
     edition = static_cast<Edition> (raw_edition);
   }
 
+  const Edition &get_edition () { return edition; }
+
   void set_metadata_output (const std::string &path)
   {
     metadata_output_path = path;
diff --git a/gcc/testsuite/rust/compile/macro-issue1395-2.rs b/gcc/testsuite/rust/compile/macro-issue1395-2.rs
new file mode 100644
index 0000000..1df6a3a
--- /dev/null
+++ b/gcc/testsuite/rust/compile/macro-issue1395-2.rs
@@ -0,0 +1,7 @@
+// { dg-additional-options "-frust-edition=2018" }
+
+macro_rules! try {
+    // { dg-error "expecting .identifier. but .try. found" "" { target *-*-* } .-1 }
+    // { dg-error "failed to parse item in crate" "" { target *-*-* } .-2 }
+    () => {};
+}
diff --git a/gcc/testsuite/rust/compile/macro-issue1395.rs b/gcc/testsuite/rust/compile/macro-issue1395.rs
new file mode 100644
index 0000000..b0368c1
--- /dev/null
+++ b/gcc/testsuite/rust/compile/macro-issue1395.rs
@@ -0,0 +1,5 @@
+// Default edition is 2015 - this is valid
+
+macro_rules! try {
+    () => {};
+}