resolve: fix bug in resolve.block.String

Fixes #115

Change-Id: Iee8933f47b0fdf34235d5a2a9be01102c9730a19

resolve/resolve.go

diff --git a/resolve/resolve.go b/resolve/resolve.go
index 676b811..0843bad 100644
--- a/resolve/resolve.go
+++ b/resolve/resolve.go
@@ -271,7 +271,7 @@
 		return "function block at " + fmt.Sprint(b.function.Span())
 	}
 	if b.comp != nil {
-		return "comprehension block at " + fmt.Sprint(b.function.Span())
+		return "comprehension block at " + fmt.Sprint(b.comp.Span())
 	}
 	return "module block"
 }