cranelift_wasm: expose the original Wasm function signature

In the `ModuleEnvironment::declare_signature` callback, also pass the original
Wasm function signature, so that consumers may associate this information with
each compiled function. This is often necessary because while each Wasm
signature gets compiled down into a single native signature, multiple Wasm
signatures might compile down into the same native signature, and in these cases
the original Wasm signature is required for dynamic type checking of calls.

crates/environ/src/module_environ.rs

@@ -7,7 +7,7 @@ use cranelift_entity::PrimaryMap;
 use cranelift_wasm::{
     self, translate_module, DataIndex, DefinedFuncIndex, ElemIndex, FuncIndex, Global, GlobalIndex,
     Memory, MemoryIndex, ModuleTranslationState, SignatureIndex, Table, TableIndex,
-    TargetEnvironment, WasmError, WasmResult,
+    TargetEnvironment, WasmError, WasmFuncType, WasmResult,
 };
 use std::convert::TryFrom;
 use std::sync::Arc;
@@ -106,7 +106,7 @@ impl<'data> cranelift_wasm::ModuleEnvironment<'data> for ModuleEnvironment<'data
         Ok(())
     }
 
-    fn declare_signature(&mut self, sig: ir::Signature) -> WasmResult<()> {
+    fn declare_signature(&mut self, _wasm: &WasmFuncType, sig: ir::Signature) -> WasmResult<()> {
         let sig = translate_signature(sig, self.pointer_type());
         // TODO: Deduplicate signatures.
         self.result.module.local.signatures.push(sig);