Sort out compile time value handling, so Rakudo can do it without using annotations.

Author: jnthn

src/QAST/CompileTimeValue.nqp

@@ -1,5 +1,16 @@
 # Composed or mixed in to any node that also has a compile-time known value.
 role QAST::CompileTimeValue {
-    has $!value;
-    method value(*@value) { $!value := @value[0] if @value; $!value }
+    has $!compile_time_value;
+    
+    method has_compile_time_value() {
+        1
+    }
+    
+    method compile_time_value() {
+        $!compile_time_value
+    }
+    
+    method set_compile_time_value($value) {
+        $!compile_time_value := $value
+    }
 }

src/QAST/Node.nqp

@@ -50,6 +50,15 @@ class QAST::Node {
         }
     }
 
+    method has_compile_time_value() {
+        0
+    }
+    
+    method set_compile_time_value($value) {
+        self.HOW.mixin(self, QAST::CompileTimeValue);
+        self.set_compile_time_value($value);
+    }
+    
     method list()          { @!array }
     method pop()           { nqp::pop(self.list) }
     method push($value)    { nqp::push(self.list, $value) }

src/QAST/WVal.nqp

@@ -1,2 +1,7 @@
 class QAST::WVal is QAST::Node does QAST::CompileTimeValue {
+    method value(*@value) {
+        @value
+            ?? self.set_compile_time_value(@value[0])
+            !! self.compile_time_value()
+    }
 }

src/QAST/Want.nqp

@@ -1,2 +1,11 @@
 class QAST::Want is QAST::Node {
+    method has_compile_time_value() {
+        nqp::istype(self[0], QAST::Node)
+            ?? self[0].has_compile_time_value()
+            !! 0
+    }
+    
+    method compile_time_value() {
+        self[0].compile_time_value()
+    }
 }