diff --git a/guix/packages.scm b/guix/packages.scm
index d3fa72fd09..26e82050f8 100644
--- a/guix/packages.scm
+++ b/guix/packages.scm
@@ -108,6 +108,7 @@
             package-superseded
             deprecated-package
             package-field-location
+            package-argument-location
 
             this-package-input
             this-package-native-input
@@ -515,9 +516,9 @@ object."
     (name old-name)
     (properties `((superseded . ,p)))))
 
-(define (package-field-location package field)
-  "Return the source code location of the definition of FIELD for PACKAGE, or
-#f if it could not be determined."
+(define (package-part-location package proc)
+  "Return the source code location of the part of PACKAGE returned by (PROC
+PACKAGE), or #f if it could not be determined."
   (match (package-location package)
     (($ <location> file line column)
      (match (search-path %load-path file)
@@ -530,17 +531,16 @@ object."
                 (go-to-location port line column)
                 (match (read port)
                   (('package inits ...)
-                   (let ((field (assoc field inits)))
-                     (match field
-                       ((_ value)
-                        (let ((loc (and=> (source-properties value)
-                                          source-properties->location)))
-                          (and loc
-                               ;; Preserve the original file name, which may be a
-                               ;; relative file name.
-                               (set-field loc (location-file) file))))
-                       (_
-                        #f))))
+                   (match (proc inits)
+                     (#f
+                      #f)
+                     (value
+                      (let ((loc (and=> (source-properties value)
+                                        source-properties->location)))
+                        (and loc
+                             ;; Preserve the original file name, which may be a
+                             ;; relative file name.
+                             (set-field loc (location-file) file))))))
                   (_
                    #f)))))
           (lambda _
@@ -550,6 +550,29 @@ object."
         #f)))
     (_ #f)))
 
+(define (package-field-location package field)
+  "Return the source code location of the definition of FIELD for PACKAGE, or
+#f if it could not be determined."
+  (package-part-location
+   package
+   (lambda (p)
+     (match (assoc field p)
+       ((_ value) value)
+       (_ #f)))))
+
+(define (package-argument-location package argument)
+  "Return the source code location of the definition of keyword ARGUMENT for
+PACKAGE, or #f if it could not be determined."
+  (package-part-location
+   package
+   (lambda (p)
+     (match (assoc 'arguments p)
+       ((_ ('quasiquote (arguments ..1)))
+        (match (member argument arguments eq?)
+          ((_ value . _) value)
+          (_ #f)))
+       (_ #f)))))
+
 (define (package-input package name)
   "Return the package input NAME of PACKAGE--i.e., an input
 from the ‘inputs’ or ‘propagated-inputs’ field.  Native inputs are not
diff --git a/guix/scripts/style.scm b/guix/scripts/style.scm
index 3c100197a7..19185d924e 100644
--- a/guix/scripts/style.scm
+++ b/guix/scripts/style.scm
@@ -371,7 +371,7 @@ bailing out~%")
                           (delete ,@to-delete)
                           (prepend ,@things)))
         (location-column location))))
-    (('quasiquote (exp ...))
+    ((or ('quasiquote (exp ...)) ((or (exp ...) (? comment? exp)) ...))
      (let/ec return
        (object->string*
         `(list ,@(simplify-expressions exp inputs return))
@@ -389,6 +389,33 @@ POLICY is a symbol that defines whether to simplify inputs; it can one of
 'silent (change only if the resulting derivation is the same), 'safe (change
 only if semantics are known to be unaffected), and 'always (fearlessly
 simplify inputs!)."
+  (define (package-argument package argument)
+    (match (member argument (package-arguments package) eq?)
+      ((_ value . _) value)
+      (_ #f)))
+
+  ;; We know that the cargo build system does not use its special input labels,
+  ;; so it is always safe to simplify, but it will change the derivation. Only
+  ;; proceed if POLICY is 'safe or 'always.
+  (when (member policy '(safe always))
+    (for-each (lambda (argument)
+                (match (package-argument package argument)
+                  (#f
+                   #f)
+                  (inputs
+                   (match (package-argument-location package argument)
+                     (#f
+                      #f)
+                     (location
+                      (edit-expression
+                       (location->source-properties location)
+                       (lambda (str)
+                         (simplify-inputs location
+                                          (package-name package)
+                                          str inputs
+                                          #:label-matches? (const #t)))))))))
+              (list #:cargo-inputs #:cargo-development-inputs)))
+
   (for-each (lambda (field-name field)
               (match (field package)
                 (()
