cgen,checker: fix array map anon fn return fixed array (fix #25928) (#25977)

Author: kbkpbot

vlib/v/checker/fn.v

@@ -3512,7 +3512,17 @@ fn (mut c Checker) array_builtin_method_call(mut node ast.CallExpr, left_type as
 	// map/filter are supposed to have 1 arg only
 	mut arg_type := unaliased_left_type
 	for mut arg in node.args {
-		arg_type = c.check_expr_option_or_result_call(arg.expr, c.expr(mut arg.expr))
+		mut expr_type := c.expr(mut arg.expr)
+		if arg.expr is ast.AnonFn {
+			// fix anon fn when return is a fixed array
+			expr_sym := c.table.sym(expr_type)
+			info := expr_sym.info as ast.FnType
+			return_type_sym := c.table.sym(info.func.return_type)
+			if return_type_sym.kind == .array_fixed {
+				expr_type = c.cast_fixed_array_ret(info.func.return_type, return_type_sym)
+			}
+		}
+		arg_type = c.check_expr_option_or_result_call(arg.expr, expr_type)
 	}
 	if method_name == 'map' {
 		// eprintln('>>>>>>> map node.args[0].expr: ${node.args[0].expr}, left_type: ${left_type} | elem_typ: ${elem_typ} | arg_type: ${arg_type}')

vlib/v/gen/c/array.v

@@ -525,6 +525,7 @@ fn (mut g Gen) gen_array_map(node ast.CallExpr) {
 	} else {
 		(ret_sym.info as ast.ArrayFixed).elem_type
 	}
+	ret_elem_sym := g.table.final_sym(ret_elem_type)
 	mut ret_elem_styp := g.styp(ret_elem_type)
 	inp_elem_type := if left_is_array {
 		(inp_sym.info as ast.Array).elem_type
@@ -576,12 +577,20 @@ fn (mut g Gen) gen_array_map(node ast.CallExpr) {
 	match mut expr {
 		ast.AnonFn {
 			g.write('${ret_elem_styp} ${tmp_map_expr_result_name} = ')
+			if ret_elem_sym.kind == .array_fixed {
+				// unpack fixed array return value
+				g.writeln('{0};')
+				g.write('memcpy(&${tmp_map_expr_result_name}, ')
+			}
 			if expr.inherited_vars.len > 0 {
 				g.write_closure_fn(mut expr, var_name, closure_var)
 			} else {
 				g.gen_anon_fn_decl(mut expr)
 				g.write('${expr.decl.name}(${var_name})')
 			}
+			if ret_elem_sym.kind == .array_fixed {
+				g.write('.ret_arr, sizeof(${ret_elem_styp}))')
+			}
 		}
 		ast.Ident {
 			g.write('${ret_elem_styp} ${tmp_map_expr_result_name} = ')

vlib/v/tests/array_map_anon_return_fixed_array_test.v

@@ -0,0 +1,13 @@
+module main
+
+fn test_array_map_anon_return_fixed_array() {
+	lines := ['1,2', '3,4', '5,7']
+	coords := lines.map(fn (line string) [2]int {
+		xs, ys := line.split_once(',') or { panic('invalid input') }
+		x := xs.int()
+		y := ys.int()
+		return [x, y]!
+	})
+
+	assert coords == [[1, 2]!, [3, 4]!, [5, 7]!]
+}