js: add support for Promise.wait() (#12781)

* builtin/js: Change Promise<T,E> to Promise<T>

* js: codegen support for Promise.wait()

* checker: checker support for Promise.wait()

vlib/builtin/js/promise.js.v

@@ -14,46 +14,46 @@ pub fn JS.Promise.race(JS.Array) JS.Promise
 
 // The Promise object represents the eventual completion (or failure)
 // of an asynchronous operation and its resulting value.
-pub struct Promise<T, E> {
+pub struct Promise<T> {
 mut:
 	promise JS.Promise [noinit]
 }
 
-pub fn promise_new<T, E>(executor fn (resolve fn (T), reject fn (E))) Promise<T, E> {
+pub fn promise_new<T>(executor fn (resolve fn (T), reject fn (JS.Any))) Promise<T> {
 	promise := JS.Promise.prototype.constructor(executor)
-	return Promise<T, E>{promise}
+	return Promise<T>{promise}
 }
 
-pub fn (p Promise<T, E>) then(on_fullfilled fn (T), on_rejected fn (E)) {
+pub fn (p Promise<T>) then(on_fullfilled fn (T), on_rejected fn (JS.Any)) {
 	p.promise.then(on_fullfilled, on_rejected)
 }
 
 // catch method returns a Promise and deals with rejected cases only.
-pub fn (p Promise<T, E>) catch(callback fn (error JS.Any)) Promise<T, E> {
+pub fn (p Promise<T>) catch(callback fn (error JS.Any)) Promise<T> {
 	promise := p.promise.catch(callback)
-	return Promise<T, E>{promise}
+	return Promise<T>{promise}
 }
 
-pub fn (p Promise<T, E>) finally(callback fn ()) Promise<int, int> {
+pub fn (p Promise<T>) finally<U>(callback fn ()) Promise<JS.Any> {
 	promise := p.promise.finally(callback)
-	return Promise<int, int>{promise}
+	return Promise<JS.Any>{promise}
 }
 
 // reject<E> returns promise which was rejected because of specified error
-pub fn promise_reject<E>(error E) Promise<int, E> {
+pub fn promise_reject(error JS.Any) Promise<JS.Any> {
 	promise := JS.Promise.reject(error)
-	return Promise<int, E>{promise}
+	return Promise<JS.Any>{promise}
 }
 
 // resolve<E> returns promise which was resolved with specified value
-pub fn promise_resolve<T>(result T) Promise<T, int> {
+pub fn promise_resolve<T>(result T) Promise<T> {
-	promise := JS.Promise.resolve(error)
+	promise := JS.Promise.resolve(result)
-	return Promise<T, int>{promise}
+	return Promise<T>{promise}
 }
 
 // race returns returns a promise that fulfills or rejects as soon as one of
 //  the promises in an iterable fulfills or rejects, with the value or reason from that promise.
-pub fn promise_race<T, E>(promises []Promise<T, E>) Promise<T, E> {
+pub fn promise_race<T>(promises []Promise<T>) Promise<T> {
 	promises_ := JS.Array.prototype.constructor()
 
 	for elem in promises {
@@ -61,7 +61,7 @@ pub fn promise_race<T, E>(promises []Promise<T, E>) Promise<T, E> {
 	}
 
 	promise := JS.Promise.race(promises_)
-	return Promise<T, E>{promise}
+	return Promise<T>{promise}
 }
 
 pub fn JS.Promise.all(JS.Array) JS.Promise

vlib/v/checker/checker.v

@@ -2044,6 +2044,16 @@ pub fn (mut c Checker) method_call(mut node ast.CallExpr) ast.Type {
 			node.return_type = final_left_sym.info.elem_type
 			return node.return_type
 		}
+	} else if c.pref.backend.is_js() && left_sym.name.starts_with('Promise<')
+		&& method_name == 'wait' {
+		info := left_sym.info as ast.Struct
+		if node.args.len > 0 {
+			c.error('wait() does not have any arguments', node.args[0].pos)
+		}
+		c.table.cur_fn.has_await = true
+		node.return_type = info.concrete_types[0]
+		node.return_type.set_flag(.optional)
+		return node.return_type
 	} else if left_sym.kind == .thread && method_name == 'wait' {
 		info := left_sym.info as ast.Thread
 		if node.args.len > 0 {

vlib/v/gen/js/fn.v

@@ -190,9 +190,15 @@ fn (mut g JsGen) method_call(node ast.CallExpr) {
 		g.gen_expr_to_string(node.left, node.left_type)
 		return
 	}
+	is_async := node.name == 'wait'
+		&& g.table.get_type_symbol(node.receiver_type).name.starts_with('Promise<')
 	call_return_is_optional := it.return_type.has_flag(.optional)
 	if call_return_is_optional {
+		if is_async {
+			g.writeln('(async function (){')
+		} else {
 			g.writeln('(function(){')
+		}
 		g.inc_indent()
 		g.writeln('try {')
 		g.inc_indent()
@@ -308,9 +314,15 @@ fn (mut g JsGen) method_call(node ast.CallExpr) {
 			receiver_type_name = 'array'
 		}
 	}
+
+	if is_async {
+		g.write('await ')
+		g.expr(it.left)
+		g.write('.promise')
+	} else {
 		mut name := util.no_dots('${receiver_type_name}_$node.name')
 
-	// name = g.generic_fn_name(node.concrete_types, name, false)
+		name = g.generic_fn_name(node.concrete_types, name, false)
 		g.write('${name}(')
 		g.expr(it.left)
 		g.gen_deref_ptr(it.left_type)
@@ -322,6 +334,7 @@ fn (mut g JsGen) method_call(node ast.CallExpr) {
 			}
 		}
 		g.write(')')
+	}
 
 	if call_return_is_optional {
 		// end unwrap
@@ -406,6 +419,7 @@ fn (mut g JsGen) gen_call_expr(it ast.CallExpr) {
 		g.write(')')
 		return
 	}
+	name = g.generic_fn_name(node.concrete_types, name, false)
 	g.expr(it.left)
 
 	g.write('${name}(')
@@ -589,7 +603,7 @@ fn (mut g JsGen) gen_method_decl(it ast.FnDecl, typ FnGenType) {
 	}
 	name = g.js_name(name)
 
-	// name = g.generic_fn_name(g.table.cur_concrete_types, name, true)
+	name = g.generic_fn_name(g.cur_concrete_types, name, true)
 	if name in parser.builtin_functions {
 		name = 'builtin__$name'
 	}