Remove HostRef<T> from the C API (#1926)

This commit removes `HostRef<T>` from the C API which only served the
purpose now of converting each type to a `wasm_ref_t*`. Our
implementation, however, does not guarantee that you'll get the same
`wasm_ref_t*` for each actual underlying item (e.g. if you put a func in
a table and then get the func as an export and from the table then
`same` will report `false`). Additionally the fate of `wasm_ref_t*`
seems somewhat unclear at this point.

The change here is to make the `same` and cast functions all abort
saying they're unimplemented. (similar to the host info functions). If
and when we get around to reimplementing these functions we can ensure
they're implemented uniformly and work well for all intended use cases.

crates/c-api/src/wasi.rs

@@ -1,6 +1,5 @@
 //! The WASI embedding API definitions for Wasmtime.
-use crate::host_ref::HostRef;
-use crate::{wasm_extern_t, wasm_importtype_t, wasm_store_t, wasm_trap_t, ExternHost};
+use crate::{wasm_extern_t, wasm_importtype_t, wasm_store_t, wasm_trap_t};
 use anyhow::Result;
 use std::collections::HashMap;
 use std::ffi::CStr;
@@ -13,7 +12,7 @@ use wasi_common::{
     old::snapshot_0::WasiCtxBuilder as WasiSnapshot0CtxBuilder, preopen_dir,
     WasiCtxBuilder as WasiPreview1CtxBuilder,
 };
-use wasmtime::{Linker, Store, Trap};
+use wasmtime::{Extern, Linker, Store, Trap};
 use wasmtime_wasi::{old::snapshot_0::Wasi as WasiSnapshot0, Wasi as WasiPreview1};
 
 unsafe fn cstr_to_path<'a>(path: *const c_char) -> Option<&'a Path> {
@@ -313,9 +312,7 @@ pub unsafe extern "C" fn wasi_instance_new(
             export_cache: HashMap::new(),
         })),
         Err(e) => {
-            *trap = Box::into_raw(Box::new(wasm_trap_t {
-                trap: HostRef::new(Trap::new(e)),
-            }));
+            *trap = Box::into_raw(Box::new(wasm_trap_t { trap: Trap::new(e) }));
 
             None
         }
@@ -358,7 +355,7 @@ pub extern "C" fn wasi_instance_bind_import<'a>(
         .entry(name.to_string())
         .or_insert_with(|| {
             Box::new(wasm_extern_t {
-                which: ExternHost::Func(HostRef::new(export.clone())),
+                which: Extern::Func(export.clone()),
             })
         });
     Some(entry)