Refactor the TypeTables type (#3971)

* Remove duplicate `TypeTables` type

This was once needed historically but it is no longer needed.

* Make the internals of `TypeTables` private

Instead of reaching internally for the `wasm_signatures` map an `Index`
implementation now exists to indirect accesses through the type of the
index being accessed. For the component model this table of types will
grow a number of other tables and this'll assist in consuming sites not
having to worry so much about which map they're reaching into.

crates/jit/src/instantiate.rs

@@ -17,7 +17,7 @@ use std::sync::Arc;
 use thiserror::Error;
 use wasmtime_environ::{
     CompileError, DefinedFuncIndex, FuncIndex, FunctionInfo, Module, ModuleTranslation, PrimaryMap,
-    SignatureIndex, StackMapInformation, Trampoline, Tunables, WasmFuncType, ELF_WASMTIME_ADDRMAP,
+    SignatureIndex, StackMapInformation, Trampoline, Tunables, ELF_WASMTIME_ADDRMAP,
     ELF_WASMTIME_TRAPS,
 };
 use wasmtime_runtime::{
@@ -358,14 +358,6 @@ pub fn mmap_vec_from_obj(obj: Object) -> Result<MmapVec> {
     }
 }
 
-/// This is intended to mirror the type tables in `wasmtime_environ`, except that
-/// it doesn't store the native signatures which are no longer needed past compilation.
-#[derive(Serialize, Deserialize)]
-#[allow(missing_docs)]
-pub struct TypeTables {
-    pub wasm_signatures: PrimaryMap<SignatureIndex, WasmFuncType>,
-}
-
 /// A compiled wasm module, ready to be instantiated.
 pub struct CompiledModule {
     wasm_data: Range<usize>,

crates/jit/src/lib.rs

@@ -30,7 +30,7 @@ mod unwind;
 pub use crate::code_memory::CodeMemory;
 pub use crate::instantiate::{
     finish_compile, mmap_vec_from_obj, subslice_range, CompiledModule, CompiledModuleInfo,
-    SetupError, SymbolizeContext, TypeTables,
+    SetupError, SymbolizeContext,
 };
 pub use demangling::*;
 pub use profiling::*;