[vala/wip/baedert/nullable: 14/25] expression: Add get_null_state vfunc

[Timm Bäder <baedert src gnome org>]

commit f56fae538f12060d650ac6781f3c57d79535a5c9
Author: Timm Bäder <mail baedert org>
Date:   Mon Nov 7 19:29:30 2016 +0100

    expression: Add get_null_state vfunc

 vala/valaexpression.vala  |   11 +++++++++++
 vala/valaliteral.vala     |    4 ++++
 vala/valanullliteral.vala |    4 ++++
 3 files changed, 19 insertions(+), 0 deletions(-)
---
diff --git a/vala/valaexpression.vala b/vala/valaexpression.vala
index 5f7a023..28a536d 100644
--- a/vala/valaexpression.vala
+++ b/vala/valaexpression.vala
@@ -22,6 +22,13 @@
 
 using GLib;
 
+
+public enum Vala.NullabilityState {
+       NULL,
+       NON_NULL,
+       NULLABLE
+}
+
 /**
  * Base class for all code nodes that might be used as an expression.
  */
@@ -71,6 +78,10 @@ public abstract class Vala.Expression : CodeNode {
         */
        public abstract bool is_pure ();
 
+       public virtual NullabilityState get_null_state () {
+               return NullabilityState.NULLABLE;
+       }
+
        /**
         * Returns whether this expression is guaranteed to be non-null.
         */
diff --git a/vala/valaliteral.vala b/vala/valaliteral.vala
index 62f17a3..3550ff7 100644
--- a/vala/valaliteral.vala
+++ b/vala/valaliteral.vala
@@ -33,4 +33,8 @@ public abstract class Vala.Literal : Expression {
        public override bool is_pure () {
                return true;
        }
+
+       public override NullabilityState get_null_state () {
+               return NullabilityState.NON_NULL;
+       }
 }
diff --git a/vala/valanullliteral.vala b/vala/valanullliteral.vala
index b5f95d0..015dd7e 100644
--- a/vala/valanullliteral.vala
+++ b/vala/valanullliteral.vala
@@ -50,6 +50,10 @@ public class Vala.NullLiteral : Literal {
                return true;
        }
 
+       public override NullabilityState get_null_state () {
+               return NullabilityState.NULL;
+       }
+
        public override bool check (CodeContext context) {
                if (checked) {
                        return !error;