From 58b777d0f15df1ffd1bfa16135030118ba7c26e3 Mon Sep 17 00:00:00 2001
From: brian <brian@brianweb.net>
Date: Mon, 4 Jul 2005 01:10:04 +0000
Subject: [PATCH] beginnings of type unification code

darcs-hash:20050704011004-24bed-b6a9105071161062091449ef4c969fd2bc5de9b9.gz
---
 src/org/ibex/classgen/JSSA.java |    9 +++++++--
 src/org/ibex/classgen/Type.java |   14 ++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/org/ibex/classgen/JSSA.java b/src/org/ibex/classgen/JSSA.java
index 664023f..d14efef 100644
--- a/src/org/ibex/classgen/JSSA.java
+++ b/src/org/ibex/classgen/JSSA.java
@@ -321,7 +321,11 @@ public class JSSA extends MethodGen implements CGConst {
     public class Return extends Op {
         final Expr e;
         public Return() { this(VOID_EXPR); }
-        public Return(Expr e) { this.e = e; }
+        public Return(Expr e) {
+            this.e = e; 
+            if(Type.unify(method.getReturnType(),e.getType()) != method.getReturnType())
+               throw new IllegalArgumentException("type mismatch");
+        }
         public String toString() { return e.getType() == Type.VOID ? "return" : ("return "+e.toString()); }
     }
 
@@ -425,8 +429,9 @@ public class JSSA extends MethodGen implements CGConst {
         private final Object o;
         public Constant(int i) { this(new Integer(i)); }
         public Constant(Object o) { this.o = o; }
-        public String _toString() { return o instanceof String ? "\"" + o + "\"" : o.toString(); }
+        public String _toString() { return o == null ? "null" : o instanceof String ? "\"" + o + "\"" : o.toString(); }
         public Type getType() {
+            if (o == null) return Type.NULL;
             if (o instanceof Byte) return Type.BYTE;
             if (o instanceof Short) return Type.SHORT;
             if (o instanceof Character) return Type.CHAR;
diff --git a/src/org/ibex/classgen/Type.java b/src/org/ibex/classgen/Type.java
index 28c30dd..3d77ba3 100644
--- a/src/org/ibex/classgen/Type.java
+++ b/src/org/ibex/classgen/Type.java
@@ -18,6 +18,7 @@ public abstract class Type implements CGConst {
     public static final Type BYTE = new Primitive("B", "byte");
     public static final Type CHAR = new Primitive("C", "char");
     public static final Type SHORT = new Primitive("S", "short");
+    public static final Type NULL = new Null();
     
     public static final Type.Class OBJECT = Type.Class.instance("java.lang.Object");
     public static final Type.Class STRING = Type.Class.instance("java.lang.String");
@@ -53,6 +54,15 @@ public abstract class Type implements CGConst {
     public boolean     isClass()     { return false; }
     public boolean     isArray()     { return false; }
 
+    public static Type unify(Type t1, Type t2) {
+        if(t1 == Type.NULL) return t2;
+        if(t2 == Type.NULL) return t1;
+        if(t1 == t2) return t1;
+        // FIXME: This needs to do a lot more (subclasses, etc)
+        // it probably should be in Context.java
+        return null;
+    }
+    
     // Protected/Private //////////////////////////////////////////////////////////////////////////////
 
     protected final String descriptor;
@@ -61,6 +71,10 @@ public abstract class Type implements CGConst {
         this.descriptor = descriptor;
         instances.put(descriptor, this);
     }
+    
+    public static class Null extends Type {
+        protected Null() { super(""); } // not really correct....
+    }
 
     public static class Primitive extends Type {
         private String humanReadable;
-- 
1.7.10.4