checker, cgen: fix optional with if expr (#10242)

vlib/v/checker/checker.v

@@ -5816,6 +5816,17 @@ pub fn (mut c Checker) unsafe_expr(mut node ast.UnsafeExpr) ast.Type {
 
 pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 	if_kind := if node.is_comptime { '\$if' } else { 'if' }
+	mut node_is_expr := false
+	if node.branches.len > 0 && node.has_else {
+		stmts := node.branches[0].stmts
+		if stmts.len > 0 && stmts[stmts.len - 1] is ast.ExprStmt
+			&& (stmts[stmts.len - 1] as ast.ExprStmt).typ != ast.void_type {
+			node_is_expr = true
+		}
+	}
+	if c.expected_type == ast.void_type && node_is_expr {
+		c.expected_type = c.expected_or_type
+	}
 	expr_required := c.expected_type != ast.void_type
 	former_expected_type := c.expected_type
 	node.typ = ast.void_type

vlib/v/gen/c/cgen.v

@@ -5877,7 +5877,7 @@ fn (mut g Gen) or_block(var_name string, or_block ast.OrExpr, return_type ast.Ty
 					g.inside_opt_data = true
 					g.expr_with_cast(expr_stmt.expr, expr_stmt.typ, return_type.clear_flag(.optional))
 					g.inside_opt_data = old_inside_opt_data
-					if g.inside_ternary == 0 && !(expr_stmt.expr is ast.IfExpr) {
+					if g.inside_ternary == 0 {
 						g.writeln(';')
 					}
 					g.stmt_path_pos.delete_last()

vlib/v/tests/option_if_expr_test.v

@@ -0,0 +1,16 @@
+fn f() ?int {
+	return none
+}
+
+fn test_option_if_expr() {
+	i := f() or {
+		if err is none {
+			int(0)
+		} else {
+			eprintln(err)
+			int(-1)
+		}
+	}
+	println(i)
+	assert i == 0
+}