use rustc::lint::*;
use syntax::ast;
use utils::{in_macro, snippet_block, span_lint_and_sugg, span_lint_and_then};
use utils::sugg::Sugg;
declare_clippy_lint! {
pub COLLAPSIBLE_IF,
style,
"`if`s that can be collapsed (e.g. `if x { if y { ... } }` and `else { if x { ... } }`)"
}
#[derive(Copy, Clone)]
pub struct CollapsibleIf;
impl LintPass for CollapsibleIf {
fn get_lints(&self) -> LintArray {
lint_array!(COLLAPSIBLE_IF)
}
}
impl EarlyLintPass for CollapsibleIf {
fn check_expr(&mut self, cx: &EarlyContext, expr: &ast::Expr) {
if !in_macro(expr.span) {
check_if(cx, expr)
}
}
}
fn check_if(cx: &EarlyContext, expr: &ast::Expr) {
match expr.node {
ast::ExprKind::If(ref check, ref then, ref else_) => if let Some(ref else_) = *else_ {
check_collapsible_maybe_if_let(cx, else_);
} else {
check_collapsible_no_if_let(cx, expr, check, then);
},
ast::ExprKind::IfLet(_, _, _, Some(ref else_)) => {
check_collapsible_maybe_if_let(cx, else_);
},
_ => (),
}
}
fn check_collapsible_maybe_if_let(cx: &EarlyContext, else_: &ast::Expr) {
if_chain! {
if let ast::ExprKind::Block(ref block, _) = else_.node;
if let Some(else_) = expr_block(block);
if !in_macro(else_.span);
then {
match else_.node {
ast::ExprKind::If(..) | ast::ExprKind::IfLet(..) => {
span_lint_and_sugg(cx,
COLLAPSIBLE_IF,
block.span,
"this `else { if .. }` block can be collapsed",
"try",
snippet_block(cx, else_.span, "..").into_owned());
}
_ => (),
}
}
}
}
fn check_collapsible_no_if_let(cx: &EarlyContext, expr: &ast::Expr, check: &ast::Expr, then: &ast::Block) {
if_chain! {
if let Some(inner) = expr_block(then);
if let ast::ExprKind::If(ref check_inner, ref content, None) = inner.node;
then {
if expr.span.ctxt() != inner.span.ctxt() {
return;
}
span_lint_and_then(cx, COLLAPSIBLE_IF, expr.span, "this if statement can be collapsed", |db| {
let lhs = Sugg::ast(cx, check, "..");
let rhs = Sugg::ast(cx, check_inner, "..");
db.span_suggestion(expr.span,
"try",
format!("if {} {}",
lhs.and(&rhs),
snippet_block(cx, content.span, "..")));
});
}
}
}
fn expr_block(block: &ast::Block) -> Option<&ast::Expr> {
let mut it = block.stmts.iter();
if let (Some(stmt), None) = (it.next(), it.next()) {
match stmt.node {
ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => Some(expr),
_ => None,
}
} else {
None
}
}