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|
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::{snippet, snippet_with_applicability};
use clippy_utils::{path_def_id, qpath_generic_tys};
use rustc_errors::Applicability;
use rustc_hir::{self as hir, def_id::DefId, QPath, TyKind};
use rustc_hir_analysis::hir_ty_to_ty;
use rustc_lint::LateContext;
use rustc_middle::ty::TypeVisitable;
use rustc_span::symbol::sym;
use super::{utils, REDUNDANT_ALLOCATION};
pub(super) fn check(cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, qpath: &QPath<'_>, def_id: DefId) -> bool {
let mut applicability = Applicability::MaybeIncorrect;
let outer_sym = if Some(def_id) == cx.tcx.lang_items().owned_box() {
"Box"
} else if cx.tcx.is_diagnostic_item(sym::Rc, def_id) {
"Rc"
} else if cx.tcx.is_diagnostic_item(sym::Arc, def_id) {
"Arc"
} else {
return false;
};
if let Some(span) = utils::match_borrows_parameter(cx, qpath) {
let generic_snippet = snippet_with_applicability(cx, span, "..", &mut applicability);
span_lint_and_then(
cx,
REDUNDANT_ALLOCATION,
hir_ty.span,
&format!("usage of `{outer_sym}<{generic_snippet}>`"),
|diag| {
diag.span_suggestion(hir_ty.span, "try", format!("{generic_snippet}"), applicability);
diag.note(format!(
"`{generic_snippet}` is already a pointer, `{outer_sym}<{generic_snippet}>` allocates a pointer on the heap"
));
},
);
return true;
}
let Some(ty) = qpath_generic_tys(qpath).next() else { return false };
let Some(id) = path_def_id(cx, ty) else { return false };
let (inner_sym, ty) = match cx.tcx.get_diagnostic_name(id) {
Some(sym::Arc) => ("Arc", ty),
Some(sym::Rc) => ("Rc", ty),
_ if Some(id) == cx.tcx.lang_items().owned_box() => ("Box", ty),
_ => return false,
};
let TyKind::Path(inner_qpath) = &ty.kind else {
return false
};
let inner_span = match qpath_generic_tys(inner_qpath).next() {
Some(hir_ty) => {
// Reallocation of a fat pointer causes it to become thin. `hir_ty_to_ty` is safe to use
// here because `mod.rs` guarantees this lint is only run on types outside of bodies and
// is not run on locals.
let ty = hir_ty_to_ty(cx.tcx, hir_ty);
if ty.has_escaping_bound_vars() || !ty.is_sized(cx.tcx, cx.param_env) {
return false;
}
hir_ty.span
},
None => return false,
};
if inner_sym == outer_sym {
let generic_snippet = snippet_with_applicability(cx, inner_span, "..", &mut applicability);
span_lint_and_then(
cx,
REDUNDANT_ALLOCATION,
hir_ty.span,
&format!("usage of `{outer_sym}<{inner_sym}<{generic_snippet}>>`"),
|diag| {
diag.span_suggestion(
hir_ty.span,
"try",
format!("{outer_sym}<{generic_snippet}>"),
applicability,
);
diag.note(format!(
"`{inner_sym}<{generic_snippet}>` is already on the heap, `{outer_sym}<{inner_sym}<{generic_snippet}>>` makes an extra allocation"
));
},
);
} else {
let generic_snippet = snippet(cx, inner_span, "..");
span_lint_and_then(
cx,
REDUNDANT_ALLOCATION,
hir_ty.span,
&format!("usage of `{outer_sym}<{inner_sym}<{generic_snippet}>>`"),
|diag| {
diag.note(format!(
"`{inner_sym}<{generic_snippet}>` is already on the heap, `{outer_sym}<{inner_sym}<{generic_snippet}>>` makes an extra allocation"
));
diag.help(format!(
"consider using just `{outer_sym}<{generic_snippet}>` or `{inner_sym}<{generic_snippet}>`"
));
},
);
}
true
}
|
