refactor(fe): move Lexer::diag_memory_ into caller

Currently, Lexer owns the diag_memory_ allocator. This ties the lifetime
of Diag_List to Lexer, preventing a refactor I want to perform.

Have users of Lexer pass their own diag_memory allocator into the Lexer.

Author: strager

benchmark/benchmark-lex.cpp

@@ -12,7 +12,8 @@ namespace {
 void benchmark_lex(::benchmark::State &state, String8_View raw_source) {
   Padded_String source(raw_source);
   for (auto _ : state) {
-    Lexer l(&source);
+    Monotonic_Allocator diag_memory("benchmark_lex diag_memory");
+    Lexer l(&source, &diag_memory);
     while (l.peek().type != Token_Type::end_of_file) {
       l.skip();
     }

src/quick-lint-js/fe/lex.cpp

@@ -224,13 +224,14 @@ bool look_up_in_unicode_table(const std::uint8_t* table, std::size_t table_size,
 }
 }
 
-Lexer::Lexer(Padded_String_View input)
-    : Lexer(input, Lexer_Options()) {}
+Lexer::Lexer(Padded_String_View input, Monotonic_Allocator* diag_memory)
+    : Lexer(input, diag_memory, Lexer_Options()) {}
 
-Lexer::Lexer(Padded_String_View input, Lexer_Options options)
+Lexer::Lexer(Padded_String_View input, Monotonic_Allocator* diag_memory, Lexer_Options options)
     : input_(input.data()),
       original_input_(input),
-      options_(options) {
+      options_(options),
+      diag_memory_(*diag_memory) {
   this->last_token_.end = this->input_;
   this->parse_bom_before_shebang();
   this->parse_current_token();

src/quick-lint-js/fe/lex.h

@@ -42,8 +42,9 @@ class Lexer {
     jsx,  // Allows '-'.
   };
 
-  explicit Lexer(Padded_String_View input);
-  explicit Lexer(Padded_String_View input, Lexer_Options);
+  explicit Lexer(Padded_String_View input, Monotonic_Allocator* diag_memory);
+  explicit Lexer(Padded_String_View input, Monotonic_Allocator* diag_memory,
+                 Lexer_Options);
 
   // Return information about the current token.
   const Token& peek() const { return this->last_token_; }
@@ -343,7 +344,7 @@ class Lexer {
 
   // Allocator for diagnostic-related memory, including Diag_List and temporary
   // strings.
-  Monotonic_Allocator diag_memory_{"Lexer::diag_memory_"};
+  Monotonic_Allocator& diag_memory_;
 
   Diag_List diags_ = Diag_List(&this->diag_memory_);
 

src/quick-lint-js/fe/parse.cpp

@@ -40,7 +40,7 @@ Parser_Transaction::Parser_Transaction(Lexer* l)
     : lex_transaction(l->begin_transaction()) {}
 
 Parser::Parser(Padded_String_View input, Parser_Options options)
-    : lexer_(input,
+    : lexer_(input, &this->diagnostic_memory_,
              Lexer_Options{
                  .typescript = options.typescript,
              }),

src/quick-lint-js/fe/parse.h

@@ -1092,16 +1092,17 @@ class Parser {
   Parse_Expression_Cache_Key parse_expression_cache_key_for_current_state()
       const;
 
+  // Memory used for strings in diagnostic messages.
+  // Must be initialized before lexer_.
+  Monotonic_Allocator diagnostic_memory_{"parser::diagnostic_memory_"};
+
   quick_lint_js::Lexer lexer_;
   Parser_Options options_;
   Expression_Arena expressions_;
 
   // Memory used for temporary memory allocations (e.g. vectors on the stack).
   Monotonic_Allocator temporary_memory_{"parser::temporary_memory_"};
 
-  // Memory used for strings in diagnostic messages.
-  Monotonic_Allocator diagnostic_memory_{"parser::diagnostic_memory_"};
-
   Diag_List &diags_ = this->lexer_.diags();
 
   // Memory used for TypeScript type expressions.