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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::implements_trait;
use clippy_utils::{is_expr_path_def_path, paths, sugg};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
use rustc_middle::ty::Ty;
use rustc_span::sym;
use super::FROM_ITER_INSTEAD_OF_COLLECT;
pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>], func: &hir::Expr<'_>) {
if_chain! {
if is_expr_path_def_path(cx, func, &paths::FROM_ITERATOR_METHOD);
let ty = cx.typeck_results().expr_ty(expr);
let arg_ty = cx.typeck_results().expr_ty(&args[0]);
if let Some(iter_id) = cx.tcx.get_diagnostic_item(sym::Iterator);
if implements_trait(cx, arg_ty, iter_id, &[]);
then {
// `expr` implements `FromIterator` trait
let iter_expr = sugg::Sugg::hir(cx, &args[0], "..").maybe_par();
let turbofish = extract_turbofish(cx, expr, ty);
let sugg = format!("{}.collect::<{}>()", iter_expr, turbofish);
span_lint_and_sugg(
cx,
FROM_ITER_INSTEAD_OF_COLLECT,
expr.span,
"usage of `FromIterator::from_iter`",
"use `.collect()` instead of `::from_iter()`",
sugg,
Applicability::MaybeIncorrect,
);
}
}
}
fn extract_turbofish(cx: &LateContext<'_>, expr: &hir::Expr<'_>, ty: Ty<'_>) -> String {
fn strip_angle_brackets(s: &str) -> Option<&str> {
s.strip_prefix('<')?.strip_suffix('>')
}
let call_site = expr.span.source_callsite();
if_chain! {
if let Some(snippet) = snippet_opt(cx, call_site);
let snippet_split = snippet.split("::").collect::<Vec<_>>();
if let Some((_, elements)) = snippet_split.split_last();
then {
if_chain! {
if let [type_specifier, _] = snippet_split.as_slice();
if let Some(type_specifier) = strip_angle_brackets(type_specifier);
if let Some((type_specifier, ..)) = type_specifier.split_once(" as ");
then {
type_specifier.to_string()
} else {
// is there a type specifier? (i.e.: like `<u32>` in `collections::BTreeSet::<u32>::`)
if let Some(type_specifier) = snippet_split.iter().find(|e| strip_angle_brackets(e).is_some()) {
// remove the type specifier from the path elements
let without_ts = elements.iter().filter_map(|e| {
if e == type_specifier { None } else { Some((*e).to_string()) }
}).collect::<Vec<_>>();
// join and add the type specifier at the end (i.e.: `collections::BTreeSet<u32>`)
format!("{}{}", without_ts.join("::"), type_specifier)
} else {
// type is not explicitly specified so wildcards are needed
// i.e.: 2 wildcards in `std::collections::BTreeMap<&i32, &char>`
let ty_str = ty.to_string();
let start = ty_str.find('<').unwrap_or(0);
let end = ty_str.find('>').unwrap_or(ty_str.len());
let nb_wildcard = ty_str[start..end].split(',').count();
let wildcards = format!("_{}", ", _".repeat(nb_wildcard - 1));
format!("{}<{}>", elements.join("::"), wildcards)
}
}
}
} else {
ty.to_string()
}
}
}
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