Pass the flag instead of using a global. (#893)

Arguably missed in #769 

Note, this is reminding me we have more class members to rename for `_`, but I felt it's best to use the new naming instead of adding more to clean up.

executable_semantics/syntax/BUILD

@@ -43,7 +43,6 @@ cc_library(
         "//executable_semantics/ast:paren_contents",
         "//executable_semantics/common:arena",
         "//executable_semantics/common:error",
-        "//executable_semantics/common:tracing_flag",
     ],
 )
 

executable_semantics/syntax/lexer.lpp

@@ -9,7 +9,6 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
   #include "common/check.h"
   #include "common/string_helpers.h"
-  #include "executable_semantics/common/tracing_flag.h"
   #include "executable_semantics/syntax/parse_and_lex_context.h"
   #include "executable_semantics/syntax/parser.h"
   #include "llvm/ADT/StringExtras.h"
@@ -246,8 +245,8 @@ string_literal        \"([^\\\"\n\v\f\r]|\\.)*\"
   CHECK(str.consume_front("\"") && str.consume_back("\""));
   std::optional<std::string> unescaped = Carbon::UnescapeStringLiteral(str);
   if (unescaped == std::nullopt) {
-    if (Carbon::tracing_output) {
-      // Print a newline because tracing prints an incomplete line
+    if (context.trace()) {
+      // Print a newline because trace prints an incomplete line
       // "Reading a token: ".
       llvm::errs() << "\n";
     }
@@ -279,8 +278,8 @@ string_literal        \"([^\\\"\n\v\f\r]|\\.)*\"
 }
 
 . {
-  if (Carbon::tracing_output) {
-    // Print a newline because tracing prints an incomplete line
+  if (context.trace()) {
+    // Print a newline because trace prints an incomplete line
     // "Reading a token: ".
     llvm::errs() << "\n";
   }

executable_semantics/syntax/parse.cpp

@@ -6,15 +6,14 @@
 
 #include "common/check.h"
 #include "executable_semantics/common/error.h"
-#include "executable_semantics/common/tracing_flag.h"
 #include "executable_semantics/syntax/lexer.h"
 #include "executable_semantics/syntax/parse_and_lex_context.h"
 #include "executable_semantics/syntax/parser.h"
 
 namespace Carbon {
 
-auto Parse(Nonnull<Arena*> arena, const std::string& input_file_name)
-    -> std::variant<AST, SyntaxErrorCode> {
+auto Parse(Nonnull<Arena*> arena, const std::string& input_file_name,
+           bool trace) -> std::variant<AST, SyntaxErrorCode> {
   FILE* input_file = fopen(input_file_name.c_str(), "r");
   if (input_file == nullptr) {
     FATAL_PROGRAM_ERROR_NO_LINE() << "Error opening '" << input_file_name
@@ -28,11 +27,11 @@ auto Parse(Nonnull<Arena*> arena, const std::string& input_file_name)
 
   // Prepare other parser arguments.
   std::optional<AST> ast = std::nullopt;
-  ParseAndLexContext context(arena->New<std::string>(input_file_name));
+  ParseAndLexContext context(arena->New<std::string>(input_file_name), trace);
 
   // Do the parse.
   auto parser = Parser(arena, scanner, context, &ast);
-  if (tracing_output) {
+  if (trace) {
     parser.set_debug_level(1);
   }
   auto syntax_error_code = parser();

executable_semantics/syntax/parse.h

@@ -18,8 +18,8 @@ using SyntaxErrorCode = int;
 
 // Returns the AST representing the contents of the named file, or an error code
 // if parsing fails. Allocations go into the provided arena.
-auto Parse(Nonnull<Arena*> arena, const std::string& input_file_name)
-    -> std::variant<Carbon::AST, SyntaxErrorCode>;
+auto Parse(Nonnull<Arena*> arena, const std::string& input_file_name,
+           bool trace) -> std::variant<Carbon::AST, SyntaxErrorCode>;
 
 }  // namespace Carbon
 

executable_semantics/syntax/parse_and_lex_context.h

@@ -17,8 +17,8 @@ namespace Carbon {
 class ParseAndLexContext {
  public:
   // Creates an instance analyzing the given input file.
-  ParseAndLexContext(Nonnull<const std::string*> input_file_name)
-      : input_file_name(input_file_name) {}
+  ParseAndLexContext(Nonnull<const std::string*> input_file_name, bool trace)
+      : input_file_name(input_file_name), trace_(trace) {}
 
   // Writes a syntax error diagnostic containing message to standard error.
   auto PrintDiagnostic(const std::string& message) -> void;
@@ -28,6 +28,8 @@ class ParseAndLexContext {
                           static_cast<int>(current_token_position.begin.line));
   }
 
+  auto trace() -> bool { return trace_; }
+
   // The source range of the token being (or just) lex'd.
   location current_token_position;
 
@@ -35,6 +37,8 @@ class ParseAndLexContext {
   // A path to the file processed, relative to the current working directory
   // when *this is called.
   Nonnull<const std::string*> input_file_name;
+
+  bool trace_;
 };
 
 }  // namespace Carbon