Rename Alias.of_path to Alias.of_user_written_path

And add a loc argument for correct error messages

src/build_system.ml

@@ -238,9 +238,10 @@ module Alias0 = struct
 
   let suffix = "-" ^ String.make 32 '0'
 
-  let of_path path =
+  let of_user_written_path ~loc path =
     if not (Path.is_in_build_dir path) then
-      die "Invalid alias!\nTried to reference alias %S"
+      Loc.fail loc "Invalid alias!\n\
+                    Tried to reference path outside build dir: %S"
         (Path.to_string_maybe_quoted path);
     make ~dir:(Path.parent path) (Path.basename path)
 

src/build_system.mli

@@ -99,7 +99,7 @@ module Alias : sig
 
   val make : string -> dir:Path.t -> t
 
-  val of_path : Path.t -> t
+  val of_user_written_path : loc:Loc.t -> Path.t -> t
 
   (** The following always holds:
 

src/super_context.ml

@@ -457,7 +457,9 @@ module Deps = struct
   open Dep_conf
 
   let make_alias t ~scope ~dir s =
-    Alias.of_path (Path.relative dir (expand_vars t ~scope ~dir s))
+    let loc = String_with_vars.loc s in
+    Alias.of_user_written_path ~loc
+      (Path.relative ~error_loc:loc dir (expand_vars t ~scope ~dir s))
 
   let dep t ~scope ~dir = function
     | File  s ->

test/blackbox-tests/test-cases/bad-alias-error/run.t

@@ -1,5 +1,7 @@
   $ dune runtest --root absolute-path 2>&1 | grep -v Entering
-  Invalid alias!
-  Tried to reference alias "/foo/bar"
+  File "jbuild", line 3, characters 16-24:
+  Error: Invalid alias!
+  Tried to reference path outside build dir: "/foo/bar"
   $ dune runtest --root outside-workspace 2>&1 | grep -v Entering
-  Path outside the workspace: ./../../../foobar from _build/default
+  File "jbuild", line 4, characters 16-39:
+  Error: path outside the workspace: ./../../../foobar from _build/default