feat: support nested void matching

examples/acceptance_tests/093/aiken.lock

@@ -0,0 +1,7 @@
+# This file was generated by Aiken
+# You typically do not need to edit this file
+
+requirements = []
+packages = []
+
+[etags]

examples/acceptance_tests/093/aiken.toml

@@ -0,0 +1,4 @@
+name = "thing/thing"
+version = "0.0.0"
+license = "Apache-2.0"
+description = "Aiken contracts for project 'thing/thing'"

examples/acceptance_tests/093/lib/foo.ak

@@ -0,0 +1,10 @@
+pub fn wow(a: Void) -> Int {
+  when Some(a) is {
+    Some(Void) -> 42
+    None -> 0
+  }
+}
+
+test wow_1() {
+  wow(Void) == 42
+}