checker: fix nested if expr method call (vlang#21773)

vlib/v/checker/fn.v

@@ -1819,6 +1819,19 @@ fn (mut c Checker) check_type_and_visibility(name string, type_idx int, expected
 }
 
 fn (mut c Checker) method_call(mut node ast.CallExpr) ast.Type {
+	// `(if true { 'foo.bar' } else { 'foo.bar.baz' }).all_after('foo.')`
+	mut left_expr := node.left
+	for mut left_expr is ast.ParExpr {
+		left_expr = left_expr.expr
+	}
+	if mut left_expr is ast.IfExpr {
+		if left_expr.branches.len > 0 && left_expr.has_else {
+			mut last_stmt := left_expr.branches[0].stmts.last()
+			if mut last_stmt is ast.ExprStmt {
+				c.expected_type = c.expr(mut last_stmt.expr)
+			}
+		}
+	}
 	left_type := c.expr(mut node.left)
 	if left_type == ast.void_type {
 		c.error('cannot call a method using an invalid expression', node.pos)

vlib/v/tests/nested_if_expr_method_call_test.v

@@ -0,0 +1,33 @@
+fn test_nested_if_expr_method_call() {
+	str_from_nested_exp1 := if true {
+		if true { 'foo.bar' } else { 'foo.bar.baz' }.all_after('foo.')
+	} else {
+		'foo'
+	}
+	println(str_from_nested_exp1)
+	assert str_from_nested_exp1 == 'bar'
+
+	str_from_nested_exp2 := if true {
+		(if true { 'foo.bar' } else { 'foo.bar.baz' }).all_after('foo.')
+	} else {
+		'foo'
+	}
+	println(str_from_nested_exp2)
+	assert str_from_nested_exp2 == 'bar'
+
+	str_from_nested_exp3 := if true {
+		'foo'
+	} else {
+		if true { 'foo.bar' } else { 'foo.bar.baz' }.all_after('foo.')
+	}
+	println(str_from_nested_exp3)
+	assert str_from_nested_exp3 == 'foo'
+
+	str_from_nested_exp4 := if true {
+		'foo'
+	} else {
+		(if true { 'foo.bar' } else { 'foo.bar.baz' }).all_after('foo.')
+	}
+	println(str_from_nested_exp4)
+	assert str_from_nested_exp4 == 'foo'
+}