Reimplement define as dynamic derivation rather than alias

New syntax:

define cli: file

The rationale is we need to be able to assign the file extension (using
type/pattern-specific variables). And if it is an alias, we will assign
it to the original target type.

Note that we could still support aliases if we need to. Will need to
bring back the id member in target_type that would normally point to
itself but for an alias would point to the origin.

1 files changed, 3 insertions, 4 deletions

diff --git a/build/target b/build/target
index a1c7880..66daa66 100644
--- a/build/target
+++ b/build/target
@@ -354,15 +354,14 @@ namespace build
     const T*
     is_a () const {return dynamic_cast<const T*> (this);}
 
-    // An alias target type should be the same as its target type except
-    // for the name.
+    // Dynamic derivation to support define.
     //
-    const target_type* alias_type = nullptr;
+    const target_type* derived_type = nullptr;
 
     const target_type&
     type () const
     {
-      return alias_type != nullptr ? *alias_type : dynamic_type ();
+      return derived_type != nullptr ? *derived_type : dynamic_type ();
     }
 
     virtual const target_type& dynamic_type () const = 0;