68 lines
3.0 KiB
Rust
68 lines
3.0 KiB
Rust
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use crate::utils::{get_trait_def_id, implements_trait, paths, span_lint_and_sugg, sugg};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir as hir;
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use rustc_lint::{LateContext, LintContext};
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use rustc_middle::ty::Ty;
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use super::FROM_ITER_INSTEAD_OF_COLLECT;
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pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
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let ty = cx.typeck_results().expr_ty(expr);
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let arg_ty = cx.typeck_results().expr_ty(&args[0]);
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if_chain! {
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if let Some(from_iter_id) = get_trait_def_id(cx, &paths::FROM_ITERATOR);
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if let Some(iter_id) = get_trait_def_id(cx, &paths::ITERATOR);
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if implements_trait(cx, ty, from_iter_id, &[]) && implements_trait(cx, arg_ty, iter_id, &[]);
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then {
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// `expr` implements `FromIterator` trait
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let iter_expr = sugg::Sugg::hir(cx, &args[0], "..").maybe_par();
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let turbofish = extract_turbofish(cx, expr, ty);
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let sugg = format!("{}.collect::<{}>()", iter_expr, turbofish);
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span_lint_and_sugg(
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cx,
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FROM_ITER_INSTEAD_OF_COLLECT,
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expr.span,
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"usage of `FromIterator::from_iter`",
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"use `.collect()` instead of `::from_iter()`",
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sugg,
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Applicability::MaybeIncorrect,
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);
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}
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}
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}
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fn extract_turbofish(cx: &LateContext<'_>, expr: &hir::Expr<'_>, ty: Ty<'tcx>) -> String {
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if_chain! {
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let call_site = expr.span.source_callsite();
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if let Ok(snippet) = cx.sess().source_map().span_to_snippet(call_site);
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let snippet_split = snippet.split("::").collect::<Vec<_>>();
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if let Some((_, elements)) = snippet_split.split_last();
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then {
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// is there a type specifier? (i.e.: like `<u32>` in `collections::BTreeSet::<u32>::`)
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if let Some(type_specifier) = snippet_split.iter().find(|e| e.starts_with('<') && e.ends_with('>')) {
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// remove the type specifier from the path elements
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let without_ts = elements.iter().filter_map(|e| {
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if e == type_specifier { None } else { Some((*e).to_string()) }
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}).collect::<Vec<_>>();
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// join and add the type specifier at the end (i.e.: `collections::BTreeSet<u32>`)
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format!("{}{}", without_ts.join("::"), type_specifier)
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} else {
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// type is not explicitly specified so wildcards are needed
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// i.e.: 2 wildcards in `std::collections::BTreeMap<&i32, &char>`
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let ty_str = ty.to_string();
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let start = ty_str.find('<').unwrap_or(0);
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let end = ty_str.find('>').unwrap_or_else(|| ty_str.len());
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let nb_wildcard = ty_str[start..end].split(',').count();
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let wildcards = format!("_{}", ", _".repeat(nb_wildcard - 1));
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format!("{}<{}>", elements.join("::"), wildcards)
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}
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} else {
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ty.to_string()
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}
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}
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}
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