Beat the borrow-checker by following gen_dev structure

compiler/gen_wasm/src/lib.rs

@@ -1,2 +1,62 @@
-pub mod module;
-mod function;
+mod backend;
+
+use bumpalo::Bump;
+use parity_wasm::builder;
+use parity_wasm::elements::Internal;
+
+use roc_collections::all::{MutMap, MutSet};
+use roc_module::symbol::{Interns, Symbol};
+use roc_mono::ir::{CallType, Expr, Proc, ProcLayout, Stmt};
+use roc_mono::layout::LayoutIds;
+
+use crate::backend::WasmBackend;
+
+pub struct Env<'a> {
+    pub arena: &'a Bump, // not really using this much, parity_wasm works with std::vec a lot
+    pub interns: Interns,
+    pub exposed_to_host: MutSet<Symbol>,
+}
+
+pub fn build_module<'a>(
+    env: &'a Env,
+    procedures: MutMap<(Symbol, ProcLayout<'a>), Proc<'a>>,
+) -> Result<std::vec::Vec<u8>, String> {
+    let mut backend = WasmBackend::new();
+    let mut layout_ids = LayoutIds::default();
+
+    let mut exports = std::vec::Vec::new();
+    for ((sym, layout), proc) in procedures {
+        let function_index = backend.build_proc(proc, sym)?;
+        if env.exposed_to_host.contains(&sym) {
+            let fn_name = layout_ids
+                .get_toplevel(sym, &layout)
+                .to_symbol_string(sym, &env.interns);
+
+            let export = builder::export()
+                .field(fn_name.as_str())
+                .with_internal(Internal::Function(function_index))
+                .build();
+
+            exports.push(export);
+        }
+    }
+    let module = backend.builder.build();
+    module
+        .to_bytes()
+        .map_err(|e| -> String { format!("Error serialising Wasm module {:?}", e) })
+}
+
+// TODO: use something like this for very simple inlining
+// Create a HashMap of inlined Procs, generate each call with different Symbol arguments
+fn _is_lowlevel_wrapper<'a>(proc: Proc<'a>) -> bool {
+    match proc.body {
+        Stmt::Let(_, expr, _, Stmt::Ret(..)) => match expr {
+            Expr::Call(roc_mono::ir::Call { call_type, .. }) => match call_type {
+                CallType::LowLevel { .. } => true,
+                _ => false,
+            },
+            _ => false,
+        },
+        _ => false,
+    }
+}