start.hh: move check for nonexistent parameter file into parseParameterFile

now we don't have to pull in <fstream> in start.hh

opm/models/utils/parametersystem.cpp

@@ -559,10 +559,14 @@ void printUsage(const std::string& helpPreamble,
     }
 }
 
-void parseParameterFile(const std::string& fileName, bool overwrite)
+bool parseParameterFile(const std::string& fileName, bool overwrite)
 {
     std::set<std::string> seenKeys;
     std::ifstream ifs(fileName);
+    if (!ifs.is_open()) {
+        return false;
+    }
+
     unsigned curLineNum = 0;
     while (ifs) {
         // string and file processing in c++ is quite blunt!
@@ -624,6 +628,8 @@ void parseParameterFile(const std::string& fileName, bool overwrite)
             MetaData::tree()[canonicalKey] = value;
         }
     }
+
+    return true;
 }
 
 std::string parseCommandLineOptions(int argc,

opm/models/utils/parametersystem.hpp

@@ -146,7 +146,7 @@ parseCommandLineOptions(int argc,
  *
  * This function does some basic syntax checks.
  */
-void parseParameterFile(const std::string& fileName, bool overwrite = true);
+bool parseParameterFile(const std::string& fileName, bool overwrite = true);
 
 /*!
  * \ingroup Parameter

opm/models/utils/start.hh

@@ -44,7 +44,6 @@
 #include <dune/fem/misc/mpimanager.hh>
 #endif
 
-#include <fstream>
 #include <iostream>
 #include <sstream>
 #include <string>
@@ -145,9 +144,7 @@ static inline int setupParameters_(int argc,
         ////////////////////////////////////////////////////////////
 
         // check whether the parameter file is readable.
-        std::ifstream tmp;
-        tmp.open(paramFileName.c_str());
-        if (!tmp.is_open()) {
+        if (!Parameters::parseParameterFile(paramFileName, /*overwrite=*/false)) {
             std::ostringstream oss;
             if (myRank == 0) {
                 oss << "Parameter file \"" << paramFileName
@@ -156,9 +153,6 @@ static inline int setupParameters_(int argc,
             }
             return /*status=*/1;
         }
-
-        // read the parameter file.
-        Parameters::parseParameterFile(paramFileName, /*overwrite=*/false);
     }
 
     // make sure that no unknown parameters are encountered