Backport SourcePath from the lazy-trees branch

This introduces the SourcePath type from lazy-trees as an abstraction
for accessing files from inputs that may not be materialized in the
real filesystem (e.g. Git repositories). Currently, however, it's just
a wrapper around CanonPath, so it shouldn't change any behaviour. (On
lazy-trees, SourcePath is a <InputAccessor, CanonPath> tuple.)

1 files changed, 2 insertions, 2 deletions

diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index cd4ee5921..a6c6b947f 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -440,8 +440,8 @@ struct CmdFlakeCheck : FlakeCommand
                     if (attr->name == state->symbols.create("path")) {
                         PathSet context;
                         auto path = state->coerceToPath(attr->pos, *attr->value, context, "");
-                        if (!store->isInStore(path))
-                            throw Error("template '%s' has a bad 'path' attribute");
+                        if (!path.pathExists())
+                            throw Error("template '%s' refers to a non-existent path '%s'", attrPath, path);
                         // TODO: recursively check the flake in 'path'.
                     }
                 } else