Implement RFC 11: Redesigning Wasmtime's APIs (#2897)

Implement Wasmtime's new API as designed by RFC 11. This is quite a large commit which has had lots of discussion externally, so for more information it's best to read the RFC thread and the PR thread.

crates/runtime/src/export.rs

@@ -1,8 +1,6 @@
 use crate::vmcontext::{
     VMCallerCheckedAnyfunc, VMContext, VMGlobalDefinition, VMMemoryDefinition, VMTableDefinition,
 };
-use crate::RuntimeInstance;
-use std::any::Any;
 use std::ptr::NonNull;
 use wasmtime_environ::wasm::Global;
 use wasmtime_environ::{MemoryPlan, TablePlan};
@@ -20,16 +18,10 @@ pub enum Export {
 
     /// A global export value.
     Global(ExportGlobal),
-
-    /// An instance
-    Instance(RuntimeInstance),
-
-    /// A module
-    Module(Box<dyn Any>),
 }
 
 /// A function export value.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Copy)]
 pub struct ExportFunction {
     /// The `VMCallerCheckedAnyfunc` for this exported function.
     ///
@@ -38,6 +30,12 @@ pub struct ExportFunction {
     pub anyfunc: NonNull<VMCallerCheckedAnyfunc>,
 }
 
+// It's part of the contract of using `ExportFunction` that synchronization
+// properties are upheld, so declare that despite the raw pointers inside this
+// is send/sync.
+unsafe impl Send for ExportFunction {}
+unsafe impl Sync for ExportFunction {}
+
 impl From<ExportFunction> for Export {
     fn from(func: ExportFunction) -> Export {
         Export::Function(func)
@@ -55,6 +53,10 @@ pub struct ExportTable {
     pub table: TablePlan,
 }
 
+// See docs on send/sync for `ExportFunction` above.
+unsafe impl Send for ExportTable {}
+unsafe impl Sync for ExportTable {}
+
 impl From<ExportTable> for Export {
     fn from(func: ExportTable) -> Export {
         Export::Table(func)
@@ -72,6 +74,10 @@ pub struct ExportMemory {
     pub memory: MemoryPlan,
 }
 
+// See docs on send/sync for `ExportFunction` above.
+unsafe impl Send for ExportMemory {}
+unsafe impl Sync for ExportMemory {}
+
 impl From<ExportMemory> for Export {
     fn from(func: ExportMemory) -> Export {
         Export::Memory(func)
@@ -89,6 +95,10 @@ pub struct ExportGlobal {
     pub global: Global,
 }
 
+// See docs on send/sync for `ExportFunction` above.
+unsafe impl Send for ExportGlobal {}
+unsafe impl Sync for ExportGlobal {}
+
 impl From<ExportGlobal> for Export {
     fn from(func: ExportGlobal) -> Export {
         Export::Global(func)