gexp: Remove special meaning of forms (PACKAGE OUTPUT) in ungexp.

* guix/gexp.scm (gexp-inputs)[add-reference-inputs]: Remove clause for
  inputs of the form (PACKAGE OUTPUT).
  (gexp->sexp)[reference->sexp]: Likewise.
* tests/gexp.scm ("input list splicing"): Change 'list' to 'gexp-input'
  for glibc:debug.
  ("text-file*"): Likewise for %bootstrap-guile:out.
  ("input list splicing + gexp-input + ungexp-native-splicing"): Remove,
  now redundant.

guix/gexp.scm

@@ -312,10 +312,6 @@ (define (add-reference-inputs ref result)
        (if (direct-store-path? str)
            (cons `(,str) result)
            result))
-      (($ <gexp-input> ((? package? p) (? string? output)) _ native?)
-       ;; XXX: For now, for backward-compatibility, automatically convert a
-       ;; pair like this to an gexp-input for OUTPUT of P.
-       (add-reference-inputs (gexp-input p output native?) result))
       (($ <gexp-input> (lst ...) output native?)
        (fold-right add-reference-inputs result
                    ;; XXX: For now, automatically convert LST to a list of
@@ -373,13 +369,6 @@ (define* (reference->sexp ref #:optional native?)
                        #:output output
                        #:system system
                        #:target (if (or n? native?) #f target)))
-        (($ <gexp-input> ((? package? p) (? string? output)) _ n?)
-         ;; XXX: For backward compatibility, automatically interpret such a
-         ;; pair.
-         (package-file p
-                       #:output output
-                       #:system system
-                       #:target (if (or n? native?) #f target)))
         (($ <gexp-input> (? origin? o) output)
          (mlet %store-monad ((drv (origin->derivation o)))
            (return (derivation->output-path drv output))))

tests/gexp.scm

@@ -196,7 +196,7 @@ (define (match-input thing)
                  (gexp->sexp* exp target)))))
 
 (test-assert "input list splicing"
-  (let* ((inputs  (list (list glibc "debug") %bootstrap-guile))
+  (let* ((inputs  (list (gexp-input glibc "debug") %bootstrap-guile))
          (outputs (list (derivation->output-path
                          (package-derivation %store glibc)
                          "debug")
@@ -210,16 +210,6 @@ (define (match-input thing)
                  `(list ,@(cons 5 outputs))))))
 
 (test-assert "input list splicing + ungexp-native-splicing"
-  (let* ((inputs (list (list glibc "debug") %bootstrap-guile))
-         (exp    (gexp (list (ungexp-native-splicing (cons (+ 2 3) inputs))))))
-    (and (lset= equal?
-                `((,glibc "debug") (,%bootstrap-guile "out"))
-                (gexp-native-inputs exp))
-         (null? (gexp-inputs exp))
-         (equal? (gexp->sexp* exp)                ;native
-                 (gexp->sexp* exp "mips64el-linux")))))
-
-(test-assert "input list splicing + gexp-input + ungexp-native-splicing"
   (let* ((inputs (list (gexp-input glibc "debug") %bootstrap-guile))
          (exp    (gexp (list (ungexp-native-splicing (cons (+ 2 3) inputs))))))
     (and (lset= equal?
@@ -553,7 +543,7 @@ (define shebang
            (file (text-file "bar" "This is bar."))
            (text (text-file* "foo"
                              %bootstrap-guile "/bin/guile "
-                             `(,%bootstrap-guile "out") "/bin/guile "
+                             (gexp-input %bootstrap-guile "out") "/bin/guile "
                              drv "/bin/guile "
                              file))
            (done (built-derivations (list text)))