Fix some compilation errors.

base/file_body.hpp

@@ -2,6 +2,7 @@
 
 #include "base/file.hpp"
 
+#include <filesystem>
 #include <string>
 
 #include "base/macros.hpp"

geometry/perspective_body.hpp

@@ -80,12 +80,10 @@ Perspective<FromFrame, ToFrame>::SegmentBehindFocalPlane(
         Barycentre<Position<FromFrame>, double>(segment,
                                                 {λ, 1.0 - λ});
     if (first_is_visible) {
-      return std::make_optional<Segment<FromFrame>>(
-                 {segment.first, intercept});
+      return std::make_optional<Segment<FromFrame>>(segment.first, intercept);
     } else {
       CHECK(second_is_visible);
-      return std::make_optional<Segment<FromFrame>>(
-                 {intercept, segment.second});
+      return std::make_optional<Segment<FromFrame>>(intercept, segment.second);
     }
   }
 }

include_solution.props

@@ -9,7 +9,7 @@
   <ItemDefinitionGroup>
     <ClCompile>
       <AdditionalIncludeDirectories>$(SolutionDir).;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>SOLUTION_DIR=std::experimental::filesystem::path(R"literal($(SolutionDir))literal");TEMP_DIR=std::experimental::filesystem::path(R"literal($(SolutionDir)temp\$(Configuration)\$(Platform)\)literal");%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>SOLUTION_DIR=std::filesystem::path(R"literal($(SolutionDir))literal");TEMP_DIR=std::filesystem::path(R"literal($(SolutionDir)temp\$(Configuration)\$(Platform)\)literal");%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
   </ItemDefinitionGroup>
   <ItemGroup />

ksp_plugin_test/plugin_compatibility_test.cpp

@@ -1,4 +1,5 @@
 
+#include <filesystem>
 #include <fstream>
 #include <map>
 #include <string>

mathematica/local_error_analysis.cpp

@@ -46,7 +46,7 @@ LocalErrorAnalyser::LocalErrorAnalyser(
 }
 
 void LocalErrorAnalyser::WriteLocalErrors(
-    std::path const& path,
+    std::filesystem::path const& path,
     FixedStepSizeIntegrator<
         Ephemeris<ICRFJ2000Equator>::NewtonianMotionEquation> const&
         fine_integrator,

testing_utilities/solar_system_factory_test.cpp

@@ -76,10 +76,11 @@ class SolarSystemFactoryTest : public testing::Test {
       DegreesOfFreedom<ICRFJ2000Equator> const& tertiary_dof,
       MassiveBody const& secondary_body,
       DegreesOfFreedom<ICRFJ2000Equator> const& secondary_dof,
-      std::optional<MassiveBody const&> const& primary_body,
-      std::optional<
-          DegreesOfFreedom<ICRFJ2000Equator> const&> const primary_dof,
-      std::string message) {
+      std::optional<std::reference_wrapper<MassiveBody const>> const&
+          primary_body,
+      std::optional <std::reference_wrapper<
+          DegreesOfFreedom<ICRFJ2000Equator> const>> const& primary_dof,
+      std::string const& message) {
     RelativeDegreesOfFreedom<ICRFJ2000Equator> const tertiary_secondary =
         tertiary_dof - secondary_dof;
     KeplerOrbit<ICRFJ2000Equator> orbit{
@@ -112,15 +113,15 @@ class SolarSystemFactoryTest : public testing::Test {
       DegreesOfFreedom<ICRFJ2000Equator> const& tertiary_dof,
       MassiveBody const& secondary_body,
       DegreesOfFreedom<ICRFJ2000Equator> const& secondary_dof,
-      std::string message) {
+      std::string const& message) {
     TestStronglyBoundOrbit(excentricity,
                            relative_error,
                            tertiary_body,
                            tertiary_dof,
                            secondary_body,
                            secondary_dof,
-                           /*tertiary_body=*/std::nullopt,
-                           /*tertiary=*/std::nullopt,
+                           /*primary_body=*/std::nullopt,
+                           /*primary_dof=*/std::nullopt,
                            message);
   }