better diagnostic on Frob->stuff() when Frob:: doesn't exist

(from Richard Soderberg <rs@oregonnet.com>)

p4raw-id: //depot/perl@6306

4 files changed, 43 insertions, 4 deletions

diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index ff4f91f89b..2a4ad88cbe 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -24,6 +24,16 @@ This document describes differences between the 5.6 release and this one.
 
 =head1 New or Changed Diagnostics
 
+=over 4
+
+=item (perhaps you forgot to load "%s"?)
+
+(F) This is an educated guess made in conjunction with the message
+"Can't locate object method \"%s\" via package \"%s\"".  It often means
+that a method requires a package that has not been loaded.
+
+=back
+
 =head1 New tests
 
 =head1 Incompatible Changes
diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index 800ca4d102..c918d417b9 100644
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -747,6 +747,12 @@ the file, say, by doing C<make install>.
 functioning as a class, but that package doesn't define that particular
 method, nor does any of its base classes.  See L<perlobj>.
 
+=item (perhaps you forgot to load "%s"?)
+
+(F) This is an educated guess made in conjunction with the message
+"Can't locate object method \"%s\" via package \"%s\"".  It often means
+that a method requires a package that has not been loaded.
+
 =item Can't locate package %s for @%s::ISA
 
 (W syntax) The @ISA array contained the name of another package that
diff --git a/pp_hot.c b/pp_hot.c
index b066b21832..2775003c8a 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -2884,6 +2884,7 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
 	char* leaf = name;
 	char* sep = Nullch;
 	char* p;
+	GV* gv;
 
 	for (p = name; *p; p++) {
 	    if (*p == '\'')
@@ -2899,9 +2900,18 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
 	    packname = name;
 	    packlen = sep - name;
 	}
-	Perl_croak(aTHX_
-		   "Can't locate object method \"%s\" via package \"%s\"",
-		   leaf, packname);
+	gv = gv_fetchpv(packname, 0, SVt_PVHV);
+	if (gv && isGV(gv)) {
+	    Perl_croak(aTHX_
+		       "Can't locate object method \"%s\" via package \"%s\"",
+		       leaf, packname);
+	}
+	else {
+	    Perl_croak(aTHX_
+		       "Can't locate object method \"%s\" via package \"%s\"
+		       " (perhaps you forgot to load \"%s\"?)",
+		       leaf, packname, packname);
+	}
     }
     return isGV(gv) ? (SV*)GvCV(gv) : (SV*)gv;
 }
diff --git a/t/op/method.t b/t/op/method.t
index 1c6f3c5d9d..d2f1300690 100755
--- a/t/op/method.t
+++ b/t/op/method.t
@@ -4,7 +4,7 @@
 # test method calls and autoloading.
 #
 
-print "1..49\n";
+print "1..53\n";
 
 @A::ISA = 'B';
 @B::ISA = 'C';
@@ -167,3 +167,16 @@ test(defined(@{"unknown_package::ISA"}) ? "defined" : "undefined", "undefined");
     test(do { eval 'A2::foo()'; $@ ? 1 : 0}, 1);
     test(A2->foo(), "foo");
 }
+
+{
+    test(do { use Config; eval 'Config->foo()';
+	      $@ =~ /^\QCan't locate object method "foo" via package "Config" at/ ? 1 : $@}, 1);
+    test(do { use Config; eval '$d = bless {}, "Config"; $d->foo()';
+	      $@ =~ /^\QCan't locate object method "foo" via package "Config" at/ ? 1 : $@}, 1);
+}
+
+test(do { eval 'E->foo()';
+	  $@ =~ /^\QCan't locate object method "foo" via package "E" (perhaps / ? 1 : $@}, 1);
+test(do { eval '$e = bless {}, "E"; $e->foo()';
+	  $@ =~ /^\QCan't locate object method "foo" via package "E" (perhaps / ? 1 : $@}, 1);
+