Remove the Context type from wasmtime (#825)

* Remove the `Context` type from `wasmtime`

This hasn't really ended up being used in all that many places and the
dependencies on it were pretty minimal. This commit removes it in favor
of simplifying its various users a bit and/or leveraging the
`Engine`/`Store` structures where possible.

* Run rustfmt

crates/api/src/instance.rs

@@ -1,4 +1,3 @@
-use crate::context::Context;
 use crate::externals::Extern;
 use crate::module::Module;
 use crate::runtime::Store;
@@ -6,9 +5,6 @@ use crate::trampoline::take_api_trap;
 use crate::trap::Trap;
 use crate::types::{ExportType, ExternType};
 use anyhow::{Error, Result};
-use std::cell::RefCell;
-use std::collections::{HashMap, HashSet};
-use std::rc::Rc;
 use wasmtime_jit::{CompiledModule, Resolver};
 use wasmtime_runtime::{Export, InstanceHandle, InstantiationError};
 
@@ -29,19 +25,15 @@ fn instantiate_in_context(
     data: &[u8],
     imports: &[Extern],
     module_name: Option<&str>,
-    context: Context,
-    exports: Rc<RefCell<HashMap<String, Option<wasmtime_runtime::Export>>>>,
-) -> Result<(InstanceHandle, HashSet<Context>), Error> {
-    let mut contexts = HashSet::new();
-    let debug_info = context.debug_info();
+) -> Result<InstanceHandle> {
     let mut resolver = SimpleResolver { imports };
     let mut compiled_module = CompiledModule::new(
-        &mut context.compiler(),
+        &mut store.compiler_mut(),
         data,
         module_name,
         &mut resolver,
-        exports,
-        debug_info,
+        store.global_exports().clone(),
+        store.engine().config().debug_info,
     )?;
 
     // Register all module signatures
@@ -58,34 +50,24 @@ fn instantiate_in_context(
             e.into()
         }
     })?;
-    contexts.insert(context);
-    Ok((instance, contexts))
+    Ok(instance)
 }
 
 #[derive(Clone)]
 pub struct Instance {
     instance_handle: InstanceHandle,
-
     module: Module,
-
-    // We need to keep CodeMemory alive.
-    contexts: HashSet<Context>,
-
     exports: Box<[Extern]>,
 }
 
 impl Instance {
     pub fn new(module: &Module, externs: &[Extern]) -> Result<Instance, Error> {
         let store = module.store();
-        let context = store.context().clone();
-        let exports = store.global_exports().clone();
-        let (mut instance_handle, contexts) = instantiate_in_context(
-            module.store(),
+        let mut instance_handle = instantiate_in_context(
+            store,
             module.binary().expect("binary"),
             externs,
             module.name(),
-            context,
-            exports,
         )?;
 
         let exports = {
@@ -104,7 +86,6 @@ impl Instance {
         Ok(Instance {
             instance_handle,
             module: module.clone(),
-            contexts,
             exports,
         })
     }
@@ -141,8 +122,6 @@ impl Instance {
     }
 
     pub fn from_handle(store: &Store, instance_handle: InstanceHandle) -> Instance {
-        let contexts = HashSet::new();
-
         let mut exports = Vec::new();
         let mut exports_types = Vec::new();
         let mut mutable = instance_handle.clone();
@@ -175,7 +154,6 @@ impl Instance {
         Instance {
             instance_handle,
             module,
-            contexts,
             exports: exports.into_boxed_slice(),
         }
     }