Fill out MultiDimArray base class.

Has the storage-type-independent bits.

src/vm/jvm/runtime/org/perl6/nqp/sixmodel/reprs/MultiDimArray.java

@@ -20,7 +20,17 @@ public SixModelObject type_object_for(ThreadContext tc, SixModelObject HOW) {
     }
 
     public SixModelObject allocate(ThreadContext tc, STable st) {
-        throw ExceptionHandling.dieInternal(tc, "allocate NYI");
+        MultiDimArrayREPRData rd = (MultiDimArrayREPRData)st.REPRData;
+        if (rd != null) {
+            MultiDimArrayInstanceBase obj = new MultiDimArrayInstanceBase();
+            obj.dimensions = new long[rd.numDimensions];
+            obj.st = st;
+            return obj;
+        }
+        else {
+            throw ExceptionHandling.dieInternal(tc,
+                 "Cannot allocate a multi-dim array type before it is composed");
+        }
     }
 
     public void compose(ThreadContext tc, STable st, SixModelObject repr_info) {

src/vm/jvm/runtime/org/perl6/nqp/sixmodel/reprs/MultiDimArrayInstanceBase.java

@@ -0,0 +1,27 @@
+package org.perl6.nqp.sixmodel.reprs;
+
+import java.lang.System;
+
+import org.perl6.nqp.runtime.ExceptionHandling;
+import org.perl6.nqp.runtime.ThreadContext;
+import org.perl6.nqp.sixmodel.SixModelObject;
+
+public class MultiDimArrayInstanceBase extends SixModelObject {
+    public long[] dimensions;
+
+    public long[] dimensions(ThreadContext tc) {
+        return dimensions;
+    }
+
+    public void set_dimensions(ThreadContext tc, long[] dims) {
+        MultiDimArrayREPRData rd = (MultiDimArrayREPRData)this.st.REPRData;
+        if (rd.numDimensions == dims.length) {
+            System.arraycopy(dims, 0, this.dimensions, 0, dims.length);
+        }
+        else {
+            throw ExceptionHandling.dieInternal(tc, String.format(
+                "Array type of %d dimensions cannot be initialized with %d dimensions",
+                rd.numDimensions, dims.length));
+        }
+    }
+}