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fix(codegen-deno): async-context IIFE wrappers (Refs #122) #126

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Merged
hyperpolymath merged 1 commit into from
May 16, 2026
Merged

fix(codegen-deno): async-context IIFE wrappers (Refs #122) #126

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41 changes: 29 additions & 12 deletions lib/codegen_deno.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,12 @@ type codegen_ctx = {
definition shadows a same-named host intrinsic ({!deno_builtins}),
so e.g. a user `fn len(xs: IntList)` is NOT lowered to `.length`. *)
local_fns : (string, unit) Hashtbl.t;
(* True while emitting a synthesised `async` method body. The
expression-position IIFE wrappers (block/try/match/let/return) must
then be `async` and awaited, because they may contain an awaited
associated call (`(await this.m(...))`) — `await` inside a plain
`(() => {...})()` is a SyntaxError ("Unexpected reserved word"). *)
in_async : bool;
}

let create_ctx symbols = {
Expand All @@ -73,8 +79,16 @@ let create_ctx symbols = {
self_name = None;
assoc = Hashtbl.create 32;
local_fns = Hashtbl.create 64;
in_async = false;
}

(* Expression-position IIFE wrapper. In an async method body it must be
`(await (async () => { ... })())` so a contained `await` is legal;
elsewhere a plain `(() => { ... })()`. *)
let iife ctx (inner : string) : string =
if ctx.in_async then "(await (async () => { " ^ inner ^ " })())"
else "(() => { " ^ inner ^ " })()"

let emit ctx str = Buffer.add_string ctx.output str

let emit_line ctx str =
Expand Down Expand Up @@ -321,11 +335,11 @@ let rec gen_expr ctx (expr : expr) : string =
let kw = if el_mut then "let" else "const" in
(match el_body with
| Some body ->
"((() => { " ^ kw ^ " " ^ pat_str ^ " = " ^ val_str ^ "; return "
^ gen_expr ctx body ^ "; })())"
iife ctx (kw ^ " " ^ pat_str ^ " = " ^ val_str ^ "; return "
^ gen_expr ctx body ^ ";")
| None ->
"((() => { " ^ kw ^ " " ^ pat_str ^ " = " ^ val_str
^ "; return Unit; })())")
iife ctx (kw ^ " " ^ pat_str ^ " = " ^ val_str
^ "; return Unit;"))
| ExprTuple exprs | ExprArray exprs ->
"[" ^ String.concat ", " (List.map (gen_expr ctx) exprs) ^ "]"
| ExprIndex (arr, idx) ->
Expand All @@ -349,8 +363,8 @@ let rec gen_expr ctx (expr : expr) : string =
| ExprMatch { em_scrutinee; em_arms } ->
gen_match ctx em_scrutinee em_arms
| ExprBlock block -> gen_block_expr ctx block
| ExprReturn (Some e) -> "(() => { return " ^ gen_expr ctx e ^ "; })()"
| ExprReturn None -> "(() => { return Unit; })()"
| ExprReturn (Some e) -> iife ctx ("return " ^ gen_expr ctx e ^ ";")
| ExprReturn None -> iife ctx "return Unit;"
| ExprLambda { elam_params; elam_body; elam_ret_ty = _ } ->
let ps = List.map (fun (p : param) -> mangle p.p_name.name) elam_params in
"((" ^ String.concat ", " ps ^ ") => " ^ gen_expr ctx elam_body ^ ")"
Expand All @@ -367,7 +381,7 @@ let rec gen_expr ctx (expr : expr) : string =
| ExprResume (Some e) -> gen_expr ctx e
| ExprResume None -> "Unit"
| ExprUnsafe _ ->
"(() => { throw new Error('unsafe op not supported in Deno-ESM backend'); })()"
iife ctx "throw new Error('unsafe op not supported in Deno-ESM backend');"

and gen_literal (lit : literal) : string =
match lit with
Expand Down Expand Up @@ -423,7 +437,11 @@ and gen_match ctx scrutinee arms =
in
prefix ^ " " ^ gen_arms rest
in
"((" ^ scrut_var ^ ") => { " ^ gen_arms arms ^ " })(" ^ scrutinee_str ^ ")"
if ctx.in_async then
"(await (async (" ^ scrut_var ^ ") => { " ^ gen_arms arms ^ " })("
^ scrutinee_str ^ "))"
else
"((" ^ scrut_var ^ ") => { " ^ gen_arms arms ^ " })(" ^ scrutinee_str ^ ")"

and gen_pattern_test scrut pat =
match pat with
Expand Down Expand Up @@ -485,7 +503,7 @@ and gen_block_expr ctx block =
| Some e -> "return " ^ gen_expr ctx e ^ ";"
| None -> "return Unit;"
in
"(() => { " ^ Buffer.contents body ^ result ^ " })()"
iife ctx (Buffer.contents body ^ result)

and gen_try ctx body catch finally =
let body_str = gen_block_expr ctx body in
Expand All @@ -502,8 +520,7 @@ and gen_try ctx body catch finally =
| None -> ""
| Some blk -> " finally { " ^ gen_block_expr ctx blk ^ "; }"
in
"(() => { try { return " ^ body_str ^ "; } " ^ catch_str ^ finally_str
^ " })()"
iife ctx ("try { return " ^ body_str ^ "; } " ^ catch_str ^ finally_str)

(* Unwrap span markers to inspect an expression's real head. *)
and unspan = function
Expand Down Expand Up @@ -695,7 +712,7 @@ let gen_method ctx ~(recv_name : string) ~(js_name : string)
let rest_params = match fd.fd_params with _ :: t -> t | [] -> [] in
let params =
List.map (fun (p : param) -> mangle p.p_name.name) rest_params in
let ctx_m = { ctx with self_name = Some recv_name } in
let ctx_m = { ctx with self_name = Some recv_name; in_async = true } in
emit_line ctx_m
(Printf.sprintf "async %s(%s) {" (mangle js_name)
(String.concat ", " params));
Expand Down
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