use rustc::hir::*;
use rustc::lint::*;
use rustc::ty;
use syntax::ast::LitKind;
use syntax_pos::Span;
use utils::paths;
use utils::{in_macro, is_expn_of, last_path_segment, match_def_path, match_type, opt_def_id, resolve_node, snippet, span_lint_and_then, walk_ptrs_ty};
declare_clippy_lint! {
pub USELESS_FORMAT,
complexity,
"useless use of `format!`"
}
#[derive(Copy, Clone, Debug)]
pub struct Pass;
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array![USELESS_FORMAT]
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if let Some(span) = is_expn_of(expr.span, "format") {
if in_macro(span) {
return;
}
match expr.node {
ExprCall(ref fun, ref args) => {
if_chain! {
if let ExprPath(ref qpath) = fun.node;
if args.len() == 3;
if let Some(fun_def_id) = opt_def_id(resolve_node(cx, qpath, fun.hir_id));
if match_def_path(cx.tcx, fun_def_id, &paths::FMT_ARGUMENTS_NEWV1FORMATTED);
if check_single_piece(&args[0]);
if let Some(format_arg) = get_single_string_arg(cx, &args[1]);
if check_unformatted(&args[2]);
then {
let sugg = format!("{}.to_string()", snippet(cx, format_arg, "<arg>").into_owned());
span_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
db.span_suggestion(expr.span, "consider using .to_string()", sugg);
});
}
}
},
ExprMatch(ref matchee, _, _) => if let ExprTup(ref tup) = matchee.node {
if tup.is_empty() {
let sugg = format!("{}.to_string()", snippet(cx, expr.span, "<expr>").into_owned());
span_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
db.span_suggestion(span, "consider using .to_string()", sugg);
});
}
},
_ => (),
}
}
}
}
fn check_single_piece(expr: &Expr) -> bool {
if_chain! {
if let ExprAddrOf(_, ref expr) = expr.node; if let ExprArray(ref exprs) = expr.node; if exprs.len() == 1;
if let ExprLit(ref lit) = exprs[0].node;
if let LitKind::Str(ref lit, _) = lit.node;
then {
return lit.as_str().is_empty();
}
}
false
}
fn get_single_string_arg(cx: &LateContext, expr: &Expr) -> Option<Span> {
if_chain! {
if let ExprAddrOf(_, ref expr) = expr.node;
if let ExprMatch(ref match_expr, ref arms, _) = expr.node;
if arms.len() == 1;
if arms[0].pats.len() == 1;
if let PatKind::Tuple(ref pat, None) = arms[0].pats[0].node;
if pat.len() == 1;
if let ExprArray(ref exprs) = arms[0].body.node;
if exprs.len() == 1;
if let ExprCall(_, ref args) = exprs[0].node;
if args.len() == 2;
if let ExprPath(ref qpath) = args[1].node;
if let Some(fun_def_id) = opt_def_id(resolve_node(cx, qpath, args[1].hir_id));
if match_def_path(cx.tcx, fun_def_id, &paths::DISPLAY_FMT_METHOD);
then {
let ty = walk_ptrs_ty(cx.tables.pat_ty(&pat[0]));
if ty.sty == ty::TyStr || match_type(cx, ty, &paths::STRING) {
if let ExprTup(ref values) = match_expr.node {
return Some(values[0].span);
}
}
}
}
None
}
fn check_unformatted(expr: &Expr) -> bool {
if_chain! {
if let ExprAddrOf(_, ref expr) = expr.node;
if let ExprArray(ref exprs) = expr.node;
if exprs.len() == 1;
if let ExprStruct(_, ref fields, _) = exprs[0].node;
if let Some(format_field) = fields.iter().find(|f| f.name.node == "format");
if let ExprStruct(_, ref fields, _) = format_field.expr.node;
if let Some(align_field) = fields.iter().find(|f| f.name.node == "width");
if let ExprPath(ref qpath) = align_field.expr.node;
if last_path_segment(qpath).name == "Implied";
then {
return true;
}
}
false
}