fix resolve-path to always return a path (not a string)

Closes #1132

pkgs/racket-test-core/tests/racket/file.rktl

@@ -1814,4 +1814,29 @@
 
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+(let ([tf (make-temporary-file)])
+  (test tf resolve-path (path->string tf))
+  (unless (eq? 'windows (system-type))
+    (delete-file tf)
+    (make-file-or-directory-link "other.txt" tf)
+    (test (string->path "other.txt") resolve-path tf))
+  (delete-file tf)
+  (case (system-path-convention-type)
+    [(unix)
+     (test (string->path "/testing-root/testing-dir/testing-file")
+           resolve-path
+           "//testing-root/testing-dir/testing-file")
+     (test (string->path "/testing-root/testing-dir/testing-file")
+           resolve-path
+           "//testing-root////testing-dir//testing-file")]
+    [(windows)
+     (test (string->path "C:/testing-root/testing-dir/testing-file")
+           resolve-path
+           "C://testing-root/testing-dir/testing-file")
+     (test (string->path "C:/testing-root/testing-dir\\testing-file")
+           resolve-path
+           "C://testing-root////testing-dir\\\\testing-file")]))
+
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
 (report-errs)

racket/src/racket/src/file.c

@@ -4617,7 +4617,7 @@ static Scheme_Object *do_resolve_path(int argc, Scheme_Object *argv[], int guard
       return scheme_make_sized_path(buffer, len, 1);
   }
 
-  if (!expanded)
+  if (!expanded && SCHEME_PATHP(argv[0]))
     return argv[0];
   else
     return scheme_make_sized_path(filename, strlen(filename), 1);