squash all tagged union work into one commit

tests/union.rs

@@ -0,0 +1,43 @@
+use proptest::prelude::*;
+use wiggle_runtime::{
+    GuestError, GuestErrorType, GuestMemory, GuestPtr, GuestPtrMut, GuestRef, GuestRefMut,
+};
+use wiggle_test::{impl_errno, HostMemory, MemArea, WasiCtx};
+
+wiggle_generate::from_witx!({
+    witx: ["tests/union.witx"],
+    ctx: WasiCtx,
+});
+
+impl_errno!(types::Errno);
+
+impl union_example::UnionExample for WasiCtx {
+    fn get_tag(&mut self, u: &types::Reason) -> Result<types::Excuse, types::Errno> {
+        println!("GET TAG: {:?}", u);
+        Ok(types::Excuse::DogAte)
+    }
+    fn reason_mult(
+        &mut self,
+        u: &types::ReasonMut<'_>,
+        multiply_by: u32,
+    ) -> Result<(), types::Errno> {
+        match u {
+            types::ReasonMut::DogAte(fptr) => {
+                let mut f = fptr.as_ref_mut().expect("valid pointer");
+                let val = *f;
+                println!("REASON MULT DogAte({})", val);
+                *f = val * multiply_by as f32;
+            }
+            types::ReasonMut::Traffic(iptr) => {
+                let mut i = iptr.as_ref_mut().expect("valid pointer");
+                let val = *i;
+                println!("REASON MULT Traffic({})", val);
+                *i = val * multiply_by as i32;
+            }
+            types::ReasonMut::Sleeping => {
+                println!("REASON MULT Sleeping");
+            }
+        }
+        Ok(())
+    }
+}