Introduce AbstractPos

This makes the position object used in exceptions abstract, with a
method getSource() to get the source code of the file in which the
error originated. This is needed for lazy trees because source files
don't necessarily exist in the filesystem, and we don't want to make
libutil depend on the InputAccessor type in libfetcher.

1 files changed, 3 insertions, 4 deletions

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 283d2746b..7efe50324 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -368,8 +368,7 @@ void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v)
     auto output = runProgram(program, true, commandArgs);
     Expr * parsed;
     try {
-        auto base = state.positions[pos];
-        parsed = state.parseExprFromString(std::move(output), base.file);
+        parsed = state.parseExprFromString(std::move(output), "/");
     } catch (Error & e) {
         e.addTrace(state.positions[pos], "While parsing the output from '%1%'", program);
         throw;
@@ -798,7 +797,7 @@ static void prim_addErrorContext(EvalState & state, const PosIdx pos, Value * *
         v = *args[1];
     } catch (Error & e) {
         PathSet context;
-        e.addTrace(std::nullopt, state.coerceToString(pos, *args[0], context).toOwned());
+        e.addTrace(nullptr, state.coerceToString(pos, *args[0], context).toOwned());
         throw;
     }
 }
@@ -4018,7 +4017,7 @@ void EvalState::createBaseEnv()
         // the parser needs two NUL bytes as terminators; one of them
         // is implied by being a C string.
         "\0";
-    eval(parse(code, sizeof(code), foFile, derivationNixPath, "/", staticBaseEnv), *vDerivation);
+    eval(parse(code, sizeof(code), derivationNixPath, "/", staticBaseEnv), *vDerivation);
 }