Added a SolidBlockMask (#solid).

src/main/java/com/sk89q/worldedit/WorldEdit.java

@@ -84,6 +84,7 @@ import com.sk89q.worldedit.masks.InvertedMask;
 import com.sk89q.worldedit.masks.Mask;
 import com.sk89q.worldedit.masks.RandomMask;
 import com.sk89q.worldedit.masks.RegionMask;
+import com.sk89q.worldedit.masks.SolidBlockMask;
 import com.sk89q.worldedit.masks.UnderOverlayMask;
 import com.sk89q.worldedit.patterns.BlockChance;
 import com.sk89q.worldedit.patterns.ClipboardPattern;
@@ -731,6 +732,8 @@ public class WorldEdit {
         case '#':
             if (component.equalsIgnoreCase("#existing")) {
                 return new ExistingBlockMask();
+            } else if (component.equalsIgnoreCase("#solid")) {
+                return new SolidBlockMask();
             } else if (component.equalsIgnoreCase("#dregion")
                     || component.equalsIgnoreCase("#dselection")
                     || component.equalsIgnoreCase("#dsel")) {

src/main/java/com/sk89q/worldedit/masks/SolidBlockMask.java

@@ -0,0 +1,15 @@
+package com.sk89q.worldedit.masks;
+
+import com.sk89q.worldedit.EditSession;
+import com.sk89q.worldedit.Vector;
+import com.sk89q.worldedit.blocks.BlockType;
+
+/**
+ * Works like {@link ExistingBlockMask}, except also dealing with non-solid non-air blocks the same way as with air.
+ */
+public class SolidBlockMask extends AbstractMask {
+    @Override
+    public boolean matches(EditSession editSession, Vector pos) {
+        return !BlockType.canPassThrough(editSession.getBlockType(pos), editSession.getBlockData(pos));
+    }
+}