Fix incorrect message "unknown macro"

When using %{lib:..} in a non dynamic context should give us an error
straight away. Delaying the error doesn't make sense as we will not be
expanding these variables in a second step.

Signed-off-by: Rudi Grinberg <rudi.grinberg@gmail.com>

src/dune/expander.ml

@@ -1,4 +1,4 @@
-open Stdune
+open Import
 
 type expanded =
   | Static of Value.t list
@@ -333,6 +333,11 @@ let expand_and_record acc ~map_exe ~dep_kind ~expansion_kind
     | Static -> fun _ -> User_error.raise ~loc [ cannot_be_used_here pform ]
     | Dynamic -> Resolved_forms.add_ddep acc ~key
   in
+  let add_fail =
+    match expansion_kind with
+    | Static -> fun _ (f : fail) -> f.fail ()
+    | Dynamic -> Resolved_forms.add_fail
+  in
   let open Build.O in
   match (expansion : Pform.Expansion.t) with
   | Var
@@ -361,7 +366,7 @@ let expand_and_record acc ~map_exe ~dep_kind ~expansion_kind
   | Macro (Dep, s) -> Some (path_exp (relative dir s))
   | Macro (Bin, s) -> (
     match resolve_binary ~loc:(Some loc) t ~prog:s with
-    | Error fail -> Resolved_forms.add_fail acc fail
+    | Error fail -> add_fail acc fail
     | Ok path -> Some (path_exp path) )
   | Macro (Lib, s) -> (
     let lib_dep, file = parse_lib_file ~loc s in
@@ -370,14 +375,14 @@ let expand_and_record acc ~map_exe ~dep_kind ~expansion_kind
       Artifacts.Public_libs.file_of_lib t.lib_artifacts ~loc ~lib:lib_dep ~file
     with
     | Ok path -> Some (path_exp path)
-    | Error e -> Resolved_forms.add_fail acc { fail = (fun () -> raise e) } )
+    | Error e -> add_fail acc { fail = (fun () -> raise e) } )
   | Macro (Libexec, s) -> (
     let lib_dep, file = parse_lib_file ~loc s in
     Resolved_forms.add_lib_dep acc lib_dep dep_kind;
     match
       Artifacts.Public_libs.file_of_lib t.lib_artifacts ~loc ~lib:lib_dep ~file
     with
-    | Error e -> Resolved_forms.add_fail acc { fail = (fun () -> raise e) }
+    | Error e -> add_fail acc { fail = (fun () -> raise e) }
     | Ok path ->
       if (not Sys.win32) || Filename.extension s = ".exe" then
         Some (path_exp path)

test/blackbox-tests/test-cases/github1541/run.t

@@ -31,7 +31,8 @@ for libraries in the deps field:
   File "dune", line 1, characters 14-33:
   1 | (rule (deps %{lib:fakelib:bar.ml}) (target dummy) (action (with-stdout-to %{target} (echo foo))))
                     ^^^^^^^^^^^^^^^^^^^
-  Error: Unknown macro %{lib:..}
+  Error: Library "fakelib" not found.
+  Hint: try: dune external-lib-deps --missing ./dummy
   [1]
 
 for binaries in the deps field:
@@ -41,5 +42,6 @@ for binaries in the deps field:
   File "dune", line 1, characters 14-25:
   1 | (rule (deps %{bin:foobar}) (target dummy) (action (with-stdout-to %{target} (echo foo))))
                     ^^^^^^^^^^^
-  Error: Unknown macro %{bin:..}
+  Error: Program foobar not found in the tree or in PATH
+   (context: default)
   [1]