Auto merge of #11669 - y21:issue11577, r=Jarcho
new lint: `unnecessary_fallible_conversions` Closes #11577 A new lint that looks for calls such as `i64::try_from(1i32)` and suggests `i64::from(1i32)`. See lint description (and linked issue) for more details for why. There's a tiny bit of overlap with the `useless_conversion` lint, in that the other one warns `T::try_from(T)` (i.e., fallibly converting to the same type), so this lint ignores cases like `i32::try_from(1i32)` to avoid emitting two warnings for the same expression. Also, funnily enough, with this one exception, this lint would warn on exactly every case in the `useless_conversion_try` ui test that `useless_conversion` didn't cover (but never two warnings at the same time), which is neat. I did add an `#![allow]` though since we don't want interleaved warnings from multiple lints in the same uitest. changelog: new lint: `unnecessary_fallible_conversions`
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bors
commit
7d34406015
14 changed files with 291 additions and 22 deletions
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@ -430,6 +430,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
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crate::methods::TYPE_ID_ON_BOX_INFO,
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crate::methods::UNINIT_ASSUMED_INIT_INFO,
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crate::methods::UNIT_HASH_INFO,
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crate::methods::UNNECESSARY_FALLIBLE_CONVERSIONS_INFO,
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crate::methods::UNNECESSARY_FILTER_MAP_INFO,
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crate::methods::UNNECESSARY_FIND_MAP_INFO,
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crate::methods::UNNECESSARY_FOLD_INFO,
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@ -82,18 +82,18 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitSaturatingAdd {
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fn get_int_max(ty: Ty<'_>) -> Option<u128> {
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match ty.peel_refs().kind() {
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Int(IntTy::I8) => i8::max_value().try_into().ok(),
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Int(IntTy::I16) => i16::max_value().try_into().ok(),
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Int(IntTy::I32) => i32::max_value().try_into().ok(),
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Int(IntTy::I64) => i64::max_value().try_into().ok(),
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Int(IntTy::I128) => i128::max_value().try_into().ok(),
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Int(IntTy::Isize) => isize::max_value().try_into().ok(),
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Uint(UintTy::U8) => u8::max_value().try_into().ok(),
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Uint(UintTy::U16) => u16::max_value().try_into().ok(),
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Uint(UintTy::U32) => u32::max_value().try_into().ok(),
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Uint(UintTy::U64) => u64::max_value().try_into().ok(),
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Uint(UintTy::U128) => Some(u128::max_value()),
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Uint(UintTy::Usize) => usize::max_value().try_into().ok(),
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Int(IntTy::I8) => i8::MAX.try_into().ok(),
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Int(IntTy::I16) => i16::MAX.try_into().ok(),
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Int(IntTy::I32) => i32::MAX.try_into().ok(),
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Int(IntTy::I64) => i64::MAX.try_into().ok(),
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Int(IntTy::I128) => i128::MAX.try_into().ok(),
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Int(IntTy::Isize) => isize::MAX.try_into().ok(),
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Uint(UintTy::U8) => Some(u8::MAX.into()),
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Uint(UintTy::U16) => Some(u16::MAX.into()),
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Uint(UintTy::U32) => Some(u32::MAX.into()),
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Uint(UintTy::U64) => Some(u64::MAX.into()),
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Uint(UintTy::U128) => Some(u128::MAX),
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Uint(UintTy::Usize) => usize::MAX.try_into().ok(),
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_ => None,
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}
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}
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@ -99,6 +99,7 @@ mod suspicious_to_owned;
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mod type_id_on_box;
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mod uninit_assumed_init;
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mod unit_hash;
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mod unnecessary_fallible_conversions;
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mod unnecessary_filter_map;
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mod unnecessary_fold;
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mod unnecessary_iter_cloned;
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@ -3655,6 +3656,33 @@ declare_clippy_lint! {
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"cloning a `Waker` only to wake it"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for calls to `TryInto::try_into` and `TryFrom::try_from` when their infallible counterparts
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/// could be used.
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///
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/// ### Why is this bad?
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/// In those cases, the `TryInto` and `TryFrom` trait implementation is a blanket impl that forwards
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/// to `Into` or `From`, which always succeeds.
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/// The returned `Result<_, Infallible>` requires error handling to get the contained value
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/// even though the conversion can never fail.
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///
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/// ### Example
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/// ```rust
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/// let _: Result<i64, _> = 1i32.try_into();
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/// let _: Result<i64, _> = <_>::try_from(1i32);
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/// ```
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/// Use `from`/`into` instead:
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/// ```rust
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/// let _: i64 = 1i32.into();
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/// let _: i64 = <_>::from(1i32);
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/// ```
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#[clippy::version = "1.75.0"]
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pub UNNECESSARY_FALLIBLE_CONVERSIONS,
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style,
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"calling the `try_from` and `try_into` trait methods when `From`/`Into` is implemented"
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}
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pub struct Methods {
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avoid_breaking_exported_api: bool,
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msrv: Msrv,
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@ -3801,6 +3829,7 @@ impl_lint_pass!(Methods => [
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PATH_ENDS_WITH_EXT,
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REDUNDANT_AS_STR,
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WAKER_CLONE_WAKE,
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UNNECESSARY_FALLIBLE_CONVERSIONS,
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]);
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/// Extracts a method call name, args, and `Span` of the method name.
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@ -3827,6 +3856,7 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
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match expr.kind {
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hir::ExprKind::Call(func, args) => {
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from_iter_instead_of_collect::check(cx, expr, args, func);
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unnecessary_fallible_conversions::check_function(cx, expr, func);
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},
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hir::ExprKind::MethodCall(method_call, receiver, args, _) => {
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let method_span = method_call.ident.span;
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@ -4316,6 +4346,9 @@ impl Methods {
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}
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unnecessary_lazy_eval::check(cx, expr, recv, arg, "then_some");
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},
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("try_into", []) if is_trait_method(cx, expr, sym::TryInto) => {
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unnecessary_fallible_conversions::check_method(cx, expr);
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}
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("to_owned", []) => {
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if !suspicious_to_owned::check(cx, expr, recv) {
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implicit_clone::check(cx, name, expr, recv);
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119
clippy_lints/src/methods/unnecessary_fallible_conversions.rs
Normal file
119
clippy_lints/src/methods/unnecessary_fallible_conversions.rs
Normal file
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@ -0,0 +1,119 @@
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::get_parent_expr;
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use clippy_utils::ty::implements_trait;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::LateContext;
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use rustc_middle::ty;
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use rustc_span::{sym, Span};
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use super::UNNECESSARY_FALLIBLE_CONVERSIONS;
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/// What function is being called and whether that call is written as a method call or a function
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/// call
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#[derive(Copy, Clone)]
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#[expect(clippy::enum_variant_names)]
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enum FunctionKind {
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/// `T::try_from(U)`
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TryFromFunction,
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/// `t.try_into()`
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TryIntoMethod,
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/// `U::try_into(t)`
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TryIntoFunction,
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}
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fn check<'tcx>(
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cx: &LateContext<'tcx>,
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expr: &Expr<'_>,
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node_args: ty::GenericArgsRef<'tcx>,
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kind: FunctionKind,
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primary_span: Span,
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) {
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if let &[self_ty, other_ty] = node_args.as_slice()
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// useless_conversion already warns `T::try_from(T)`, so ignore it here
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&& self_ty != other_ty
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&& let Some(self_ty) = self_ty.as_type()
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&& let Some(from_into_trait) = cx.tcx.get_diagnostic_item(match kind {
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FunctionKind::TryFromFunction => sym::From,
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FunctionKind::TryIntoMethod | FunctionKind::TryIntoFunction => sym::Into,
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})
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// If `T: TryFrom<U>` and `T: From<U>` both exist, then that means that the `TryFrom`
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// _must_ be from the blanket impl and cannot have been manually implemented
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// (else there would be conflicting impls, even with #![feature(spec)]), so we don't even need to check
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// what `<T as TryFrom<U>>::Error` is: it's always `Infallible`
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&& implements_trait(cx, self_ty, from_into_trait, &[other_ty])
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{
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let parent_unwrap_call = get_parent_expr(cx, expr)
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.and_then(|parent| {
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if let ExprKind::MethodCall(path, .., span) = parent.kind
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&& let sym::unwrap | sym::expect = path.ident.name
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{
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Some(span)
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} else {
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None
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}
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});
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let (sugg, span, applicability) = match kind {
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FunctionKind::TryIntoMethod if let Some(unwrap_span) = parent_unwrap_call => {
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// Extend the span to include the unwrap/expect call:
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// `foo.try_into().expect("..")`
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// ^^^^^^^^^^^^^^^^^^^^^^^
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//
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// `try_into().unwrap()` specifically can be trivially replaced with just `into()`,
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// so that can be machine-applicable
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("into()", primary_span.with_hi(unwrap_span.hi()), Applicability::MachineApplicable)
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}
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FunctionKind::TryFromFunction => ("From::from", primary_span, Applicability::Unspecified),
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FunctionKind::TryIntoFunction => ("Into::into", primary_span, Applicability::Unspecified),
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FunctionKind::TryIntoMethod => ("into", primary_span, Applicability::Unspecified),
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};
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span_lint_and_sugg(
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cx,
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UNNECESSARY_FALLIBLE_CONVERSIONS,
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span,
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"use of a fallible conversion when an infallible one could be used",
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"use",
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sugg.into(),
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applicability
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);
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}
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}
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/// Checks method call exprs:
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/// - `0i32.try_into()`
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pub(super) fn check_method(cx: &LateContext<'_>, expr: &Expr<'_>) {
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if let ExprKind::MethodCall(path, ..) = expr.kind {
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check(
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cx,
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expr,
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cx.typeck_results().node_args(expr.hir_id),
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FunctionKind::TryIntoMethod,
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path.ident.span,
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);
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}
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}
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/// Checks function call exprs:
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/// - `<i64 as TryFrom<_>>::try_from(0i32)`
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/// - `<_ as TryInto<i64>>::try_into(0i32)`
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pub(super) fn check_function(cx: &LateContext<'_>, expr: &Expr<'_>, callee: &Expr<'_>) {
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if let ExprKind::Path(ref qpath) = callee.kind
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&& let Some(item_def_id) = cx.qpath_res(qpath, callee.hir_id).opt_def_id()
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&& let Some(trait_def_id) = cx.tcx.trait_of_item(item_def_id)
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{
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check(
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cx,
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expr,
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cx.typeck_results().node_args(callee.hir_id),
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match cx.tcx.get_diagnostic_name(trait_def_id) {
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Some(sym::TryFrom) => FunctionKind::TryFromFunction,
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Some(sym::TryInto) => FunctionKind::TryIntoFunction,
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_ => return,
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},
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callee.span,
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);
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}
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}
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