Enable multi-value in the Python extension (#541)

This commit enables the multi-value features in the Python extension
to be usable by-default with interface types. Additionally this removes
some code which panics on multi-value but doesn't end up getting used
today.

crates/misc/py/src/instance.rs

@@ -6,7 +6,6 @@ use crate::function::Function;
 use crate::memory::Memory;
 use alloc::rc::Rc;
 use core::cell::RefCell;
-use cranelift_codegen::ir::{self, types};
 use pyo3::prelude::*;
 use pyo3::types::PyDict;
 use wasmtime_environ::Export;
@@ -21,16 +20,6 @@ pub struct Instance {
     pub data: Rc<ModuleData>,
 }
 
-fn get_type_annot(ty: ir::Type) -> &'static str {
-    match ty {
-        types::I32 => "i32",
-        types::I64 => "i64",
-        types::F32 => "f32",
-        types::F64 => "f64",
-        _ => panic!("unknown type"),
-    }
-}
-
 #[pymethods]
 impl Instance {
     #[getter(exports)]
@@ -67,20 +56,10 @@ impl Instance {
         }
         for name in function_exports {
             if let Some(RuntimeExport::Function { signature, .. }) = self.instance.lookup(&name) {
-                let annot = PyDict::new(py);
                 let mut args_types = Vec::new();
                 for index in 1..signature.params.len() {
                     let ty = signature.params[index].value_type;
                     args_types.push(ty);
-                    annot.set_item(format!("param{}", index - 1), get_type_annot(ty))?;
-                }
-                match signature.returns.len() {
-                    0 => (),
-                    1 => {
-                        annot
-                            .set_item("return", get_type_annot(signature.returns[0].value_type))?;
-                    }
-                    _ => panic!("multi-return"),
                 }
                 let f = Py::new(
                     py,
@@ -92,8 +71,6 @@ impl Instance {
                         args_types,
                     },
                 )?;
-                // FIXME set the f object the `__annotations__` attribute somehow?
-                let _ = annot;
                 exports.set_item(name, f)?;
             } else {
                 panic!("function");

crates/misc/py/src/lib.rs

@@ -9,6 +9,7 @@ use pyo3::types::{PyBytes, PyDict, PySet};
 use pyo3::wrap_pyfunction;
 use std::rc::Rc;
 use wasmtime_interface_types::ModuleData;
+use wasmtime_jit::Features;
 
 mod function;
 mod import;
@@ -61,7 +62,11 @@ pub fn instantiate(
         isa_builder.finish(cranelift_codegen::settings::Flags::new(flag_builder))
     };
 
-    let mut context = wasmtime_jit::Context::with_isa(isa, wasmtime_jit::CompilationStrategy::Auto);
+    let mut context = wasmtime_jit::Context::with_isa(isa, wasmtime_jit::CompilationStrategy::Auto)
+        .with_features(Features {
+            multi_value: true,
+            ..Features::default()
+        });
     context.set_debug_info(generate_debug_info);
     let global_exports = context.get_global_exports();