Workaround a compilation issue on C++20

Summary: Workaround a compilation issue on C++20 by switching from `fmt::string_view` to `boost::string_view`. A proper fix (fmtlib/fmt#2769) will be backported separately.

Differential Revision: D37076763

fbshipit-source-id: d8001bdcd65ee9edf1f265e3aaf281c196e4d155

thrift/compiler/generate/t_mstch_cpp2_generator.cc

@@ -550,7 +550,7 @@ class mstch_cpp2_type : public mstch_type {
     return resolved_type_->is_string_or_binary() && !is_adapted();
   }
   mstch::node resolved_cpp_type() {
-    return fmt::to_string(cpp2::get_type(resolved_type_));
+    return std::string(cpp2::get_type(resolved_type_));
   }
   mstch::node is_string_or_binary() {
     return resolved_type_->is_string_or_binary();

thrift/compiler/generate/t_mstch_py3_generator.cc

@@ -1377,7 +1377,7 @@ std::shared_ptr<mstch_base> type_py3_generator<ForContainers>::generate(
         trueType,
         mstch_py3_type::CachedProperties{
             get_cpp_template(*trueType),
-            fmt::to_string(cpp2::get_type(trueType)),
+            std::string(cpp2::get_type(trueType)),
             {}});
   }
   return std::make_shared<T>(

thrift/compiler/lib/cpp2/util.cc

@@ -45,12 +45,12 @@ namespace compiler {
 namespace cpp2 {
 namespace {
 
-bool contains(fmt::string_view s, fmt::string_view what) {
+bool contains(boost::string_view s, boost::string_view what) {
   return std::search(s.begin(), s.end(), what.begin(), what.end()) != s.end();
 }
 
-fmt::string_view value_or_empty(const std::string* value) {
-  return value ? *value : std::string_view("");
+boost::string_view value_or_empty(const std::string* value) {
+  return value ? *value : boost::string_view("");
 }
 
 int checked_stoi(const std::string& s, std::string msg) {
@@ -258,7 +258,7 @@ bool is_orderable(t_type const& type) {
   return is_orderable(seen, memo, type);
 }
 
-fmt::string_view get_type(const t_type* type) {
+boost::string_view get_type(const t_type* type) {
   return value_or_empty(gen::cpp::type_resolver::find_type(*type));
 }
 

thrift/compiler/lib/cpp2/util.h

@@ -34,7 +34,7 @@
 #include <thrift/compiler/gen/cpp/namespace_resolver.h>
 #include <thrift/compiler/gen/cpp/reference_type.h>
 
-#include <fmt/format.h>
+#include <boost/utility/string_view.hpp>
 
 namespace apache {
 namespace thrift {
@@ -101,7 +101,7 @@ bool is_orderable(t_type const& type);
  * Return the cpp.type/cpp2.type attribute or empty string if nothing set.
  */
 // TODO(afuller): Replace with type_resolver::get_type_name.
-fmt::string_view get_type(const t_type* type);
+boost::string_view get_type(const t_type* type);
 
 /**
  * If the cpp_type is std::unique_ptr<folly::IOBuf> the C++ compiler implicitly