clippy_lints/src/checked_conversions.rs - rust-clippy - Git at Google

 use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::{SpanlessEq, is_in_const_context, is_integer_literal, sym};
 use rustc_errors::Applicability;
 use rustc_hir::{BinOpKind, Expr, ExprKind, QPath, TyKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_session::impl_lint_pass;
 use rustc_span::Symbol;

 declare_clippy_lint! {
     /// ### What it does
     /// Checks for explicit bounds checking when casting.
     ///
     /// ### Why is this bad?
     /// Reduces the readability of statements & is error prone.
     ///
     /// ### Example
     /// ```no_run
     /// # let foo: u32 = 5;
     /// foo <= i32::MAX as u32;
     /// ```
     ///
     /// Use instead:
     /// ```no_run
     /// # let foo = 1;
     /// # #[allow(unused)]
     /// i32::try_from(foo).is_ok();
     /// ```
     #[clippy::version = "1.37.0"]
     pub CHECKED_CONVERSIONS,
     pedantic,
     "`try_from` could replace manual bounds checking when casting"
 }

 pub struct CheckedConversions {
     msrv: Msrv,
 }

 impl CheckedConversions {
     pub fn new(conf: &'static Conf) -> Self {
         Self { msrv: conf.msrv }
     }
 }

 impl_lint_pass!(CheckedConversions => [CHECKED_CONVERSIONS]);

 impl LateLintPass<'_> for CheckedConversions {
     fn check_expr(&mut self, cx: &LateContext<'_>, item: &Expr<'_>) {
         if let ExprKind::Binary(op, lhs, rhs) = item.kind
             && let (lt1, gt1, op2) = match op.node {
                 BinOpKind::Le => (lhs, rhs, None),
                 BinOpKind::Ge => (rhs, lhs, None),
                 BinOpKind::And
                     if let ExprKind::Binary(op1, lhs1, rhs1) = lhs.kind
                         && let ExprKind::Binary(op2, lhs2, rhs2) = rhs.kind
                         && let Some((lt1, gt1)) = read_le_ge(op1.node, lhs1, rhs1)
                         && let Some((lt2, gt2)) = read_le_ge(op2.node, lhs2, rhs2) =>
                 {
                     (lt1, gt1, Some((lt2, gt2)))
                 },
                 _ => return,
             }
             && !item.span.in_external_macro(cx.sess().source_map())
             && !is_in_const_context(cx)
             && let Some(cv) = match op2 {
                 // todo: check for case signed -> larger unsigned == only x >= 0
                 None => check_upper_bound(lt1, gt1).filter(|cv| cv.cvt == ConversionType::FromUnsigned),
                 Some((lt2, gt2)) => {
                     let upper_lower = |lt1, gt1, lt2, gt2| {
                         check_upper_bound(lt1, gt1)
                             .zip(check_lower_bound(lt2, gt2))
                             .and_then(|(l, r)| l.combine(r, cx))
                     };
                     upper_lower(lt1, gt1, lt2, gt2).or_else(|| upper_lower(lt2, gt2, lt1, gt1))
                 },
             }
             && let Some(to_type) = cv.to_type
             && self.msrv.meets(cx, msrvs::TRY_FROM)
         {
             let mut applicability = Applicability::MachineApplicable;
             let snippet = snippet_with_applicability(cx, cv.expr_to_cast.span, "_", &mut applicability);
             span_lint_and_sugg(
                 cx,
                 CHECKED_CONVERSIONS,
                 item.span,
                 "checked cast can be simplified",
                 "try",
                 format!("{to_type}::try_from({snippet}).is_ok()"),
                 applicability,
             );
         }
     }
 }

 /// Contains the result of a tried conversion check
 #[derive(Clone, Debug)]
 struct Conversion<'a> {
     cvt: ConversionType,
     expr_to_cast: &'a Expr<'a>,
     to_type: Option<Symbol>,
 }

 /// The kind of conversion that is checked
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 enum ConversionType {
     SignedToUnsigned,
     SignedToSigned,
     FromUnsigned,
 }

 /// Attempts to read either `<=` or `>=` with a normalized operand order.
 fn read_le_ge<'tcx>(
     op: BinOpKind,
     lhs: &'tcx Expr<'tcx>,
     rhs: &'tcx Expr<'tcx>,
 ) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
     match op {
         BinOpKind::Le => Some((lhs, rhs)),
         BinOpKind::Ge => Some((rhs, lhs)),
         _ => None,
     }
 }

 impl<'a> Conversion<'a> {
     /// Combine multiple conversions if the are compatible
     pub fn combine(self, other: Self, cx: &LateContext<'_>) -> Option<Conversion<'a>> {
         if self.is_compatible(&other, cx) {
             // Prefer a Conversion that contains a type-constraint
             Some(if self.to_type.is_some() { self } else { other })
         } else {
             None
         }
     }

     /// Checks if two conversions are compatible
     /// same type of conversion, same 'castee' and same 'to type'
     pub fn is_compatible(&self, other: &Self, cx: &LateContext<'_>) -> bool {
         (self.cvt == other.cvt)
             && (SpanlessEq::new(cx).eq_expr(self.expr_to_cast, other.expr_to_cast))
             && (self.has_compatible_to_type(other))
     }

     /// Checks if the to-type is the same (if there is a type constraint)
     fn has_compatible_to_type(&self, other: &Self) -> bool {
         match (self.to_type, other.to_type) {
             (Some(l), Some(r)) => l == r,
             _ => true,
         }
     }

     /// Try to construct a new conversion if the conversion type is valid
     fn try_new(expr_to_cast: &'a Expr<'_>, from_type: Symbol, to_type: Symbol) -> Option<Conversion<'a>> {
         ConversionType::try_new(from_type, to_type).map(|cvt| Conversion {
             cvt,
             expr_to_cast,
             to_type: Some(to_type),
         })
     }

     /// Construct a new conversion without type constraint
     fn new_any(expr_to_cast: &'a Expr<'_>) -> Conversion<'a> {
         Conversion {
             cvt: ConversionType::SignedToUnsigned,
             expr_to_cast,
             to_type: None,
         }
     }
 }

 impl ConversionType {
     /// Creates a conversion type if the type is allowed & conversion is valid
     #[must_use]
     fn try_new(from: Symbol, to: Symbol) -> Option<Self> {
         if UINTS.contains(&from) {
             Some(Self::FromUnsigned)
         } else if SINTS.contains(&from) {
             if UINTS.contains(&to) {
                 Some(Self::SignedToUnsigned)
             } else if SINTS.contains(&to) {
                 Some(Self::SignedToSigned)
             } else {
                 None
             }
         } else {
             None
         }
     }
 }

 /// Check for `expr <= (to_type::MAX as from_type)`
 fn check_upper_bound<'tcx>(lt: &'tcx Expr<'tcx>, gt: &'tcx Expr<'tcx>) -> Option<Conversion<'tcx>> {
     if let Some((from, to)) = get_types_from_cast(gt, INTS, sym::max_value, sym::MAX) {
         Conversion::try_new(lt, from, to)
     } else {
         None
     }
 }

 /// Check for `expr >= 0|(to_type::MIN as from_type)`
 fn check_lower_bound<'tcx>(lt: &'tcx Expr<'tcx>, gt: &'tcx Expr<'tcx>) -> Option<Conversion<'tcx>> {
     check_lower_bound_zero(gt, lt).or_else(|| check_lower_bound_min(gt, lt))
 }

 /// Check for `expr >= 0`
 fn check_lower_bound_zero<'a>(candidate: &'a Expr<'_>, check: &'a Expr<'_>) -> Option<Conversion<'a>> {
     is_integer_literal(check, 0).then(|| Conversion::new_any(candidate))
 }

 /// Check for `expr >= (to_type::MIN as from_type)`
 fn check_lower_bound_min<'a>(candidate: &'a Expr<'_>, check: &'a Expr<'_>) -> Option<Conversion<'a>> {
     if let Some((from, to)) = get_types_from_cast(check, SINTS, sym::min_value, sym::MIN) {
         Conversion::try_new(candidate, from, to)
     } else {
         None
     }
 }

 /// Tries to extract the from- and to-type from a cast expression
 fn get_types_from_cast(
     expr: &Expr<'_>,
     types: &[Symbol],
     func: Symbol,
     assoc_const: Symbol,
 ) -> Option<(Symbol, Symbol)> {
     // `to_type::max_value() as from_type`
     // or `to_type::MAX as from_type`
     let call_from_cast: Option<(&Expr<'_>, Symbol)> = if let ExprKind::Cast(limit, from_type) = &expr.kind
         // to_type::max_value(), from_type
         && let TyKind::Path(from_type_path) = &from_type.kind
         && let Some(from_sym) = int_ty_to_sym(from_type_path)
     {
         Some((limit, from_sym))
     } else {
         None
     };

     // `from_type::from(to_type::max_value())`
     let limit_from: Option<(&Expr<'_>, Symbol)> = call_from_cast.or_else(|| {
         if let ExprKind::Call(from_func, [limit]) = &expr.kind
             // `from_type::from, to_type::max_value()`
             // `from_type::from`
             && let ExprKind::Path(path) = &from_func.kind
             && let Some(from_sym) = get_implementing_type(path, INTS, sym::from)
         {
             Some((limit, from_sym))
         } else {
             None
         }
     });

     if let Some((limit, from_type)) = limit_from {
         match limit.kind {
             // `from_type::from(_)`
             ExprKind::Call(path, _) => {
                 if let ExprKind::Path(ref path) = path.kind
                     // `to_type`
                     && let Some(to_type) = get_implementing_type(path, types, func)
                 {
                     return Some((from_type, to_type));
                 }
             },
             // `to_type::MAX`
             ExprKind::Path(ref path) => {
                 if let Some(to_type) = get_implementing_type(path, types, assoc_const) {
                     return Some((from_type, to_type));
                 }
             },
             _ => {},
         }
     }
     None
 }

 /// Gets the type which implements the called function
 fn get_implementing_type(path: &QPath<'_>, candidates: &[Symbol], function: Symbol) -> Option<Symbol> {
     if let QPath::TypeRelative(ty, path) = &path
         && path.ident.name == function
         && let TyKind::Path(QPath::Resolved(None, tp)) = &ty.kind
         && let [int] = tp.segments
     {
         candidates.iter().find(|c| int.ident.name == **c).copied()
     } else {
         None
     }
 }

 /// Gets the type as a string, if it is a supported integer
 fn int_ty_to_sym(path: &QPath<'_>) -> Option<Symbol> {
     if let QPath::Resolved(_, path) = *path
         && let [ty] = path.segments
     {
         INTS.iter().find(|c| ty.ident.name == **c).copied()
     } else {
         None
     }
 }

 // Constants
 const UINTS: &[Symbol] = &[sym::u8, sym::u16, sym::u32, sym::u64, sym::usize];
 const SINTS: &[Symbol] = &[sym::i8, sym::i16, sym::i32, sym::i64, sym::isize];
 const INTS: &[Symbol] = &[
     sym::u8,
     sym::u16,
     sym::u32,
     sym::u64,
     sym::usize,
     sym::i8,
     sym::i16,
     sym::i32,
     sym::i64,
     sym::isize,
 ];
	use clippy_config::Conf;
	use clippy_utils::diagnostics::span_lint_and_sugg;
	use clippy_utils::msrvs::{self, Msrv};
	use clippy_utils::source::snippet_with_applicability;
	use clippy_utils::{SpanlessEq, is_in_const_context, is_integer_literal, sym};
	use rustc_errors::Applicability;
	use rustc_hir::{BinOpKind, Expr, ExprKind, QPath, TyKind};
	use rustc_lint::{LateContext, LateLintPass, LintContext};
	use rustc_session::impl_lint_pass;
	use rustc_span::Symbol;

	declare_clippy_lint! {
	/// ### What it does
	/// Checks for explicit bounds checking when casting.
	///
	/// ### Why is this bad?
	/// Reduces the readability of statements & is error prone.
	///
	/// ### Example
	/// ```no_run
	/// # let foo: u32 = 5;
	/// foo <= i32::MAX as u32;
	/// ```
	///
	/// Use instead:
	/// ```no_run
	/// # let foo = 1;
	/// # #[allow(unused)]
	/// i32::try_from(foo).is_ok();
	/// ```
	#[clippy::version = "1.37.0"]
	pub CHECKED_CONVERSIONS,
	pedantic,
	"`try_from` could replace manual bounds checking when casting"
	}

	pub struct CheckedConversions {
	msrv: Msrv,
	}

	impl CheckedConversions {
	pub fn new(conf: &'static Conf) -> Self {
	Self { msrv: conf.msrv }
	}
	}

	impl_lint_pass!(CheckedConversions => [CHECKED_CONVERSIONS]);

	impl LateLintPass<'_> for CheckedConversions {
	fn check_expr(&mut self, cx: &LateContext<'_>, item: &Expr<'_>) {
	if let ExprKind::Binary(op, lhs, rhs) = item.kind
	&& let (lt1, gt1, op2) = match op.node {
	BinOpKind::Le => (lhs, rhs, None),
	BinOpKind::Ge => (rhs, lhs, None),
	BinOpKind::And
	if let ExprKind::Binary(op1, lhs1, rhs1) = lhs.kind
	&& let ExprKind::Binary(op2, lhs2, rhs2) = rhs.kind
	&& let Some((lt1, gt1)) = read_le_ge(op1.node, lhs1, rhs1)
	&& let Some((lt2, gt2)) = read_le_ge(op2.node, lhs2, rhs2) =>
	{
	(lt1, gt1, Some((lt2, gt2)))
	},
	_ => return,
	}
	&& !item.span.in_external_macro(cx.sess().source_map())
	&& !is_in_const_context(cx)
	&& let Some(cv) = match op2 {
	// todo: check for case signed -> larger unsigned == only x >= 0
	None => check_upper_bound(lt1, gt1).filter(\|cv\| cv.cvt == ConversionType::FromUnsigned),
	Some((lt2, gt2)) => {
	let upper_lower = \|lt1, gt1, lt2, gt2\| {
	check_upper_bound(lt1, gt1)
	.zip(check_lower_bound(lt2, gt2))
	.and_then(\|(l, r)\| l.combine(r, cx))
	};
	upper_lower(lt1, gt1, lt2, gt2).or_else(\|\| upper_lower(lt2, gt2, lt1, gt1))
	},
	}
	&& let Some(to_type) = cv.to_type
	&& self.msrv.meets(cx, msrvs::TRY_FROM)
	{
	let mut applicability = Applicability::MachineApplicable;
	let snippet = snippet_with_applicability(cx, cv.expr_to_cast.span, "_", &mut applicability);
	span_lint_and_sugg(
	cx,
	CHECKED_CONVERSIONS,
	item.span,
	"checked cast can be simplified",
	"try",
	format!("{to_type}::try_from({snippet}).is_ok()"),
	applicability,
	);
	}
	}
	}

	/// Contains the result of a tried conversion check
	#[derive(Clone, Debug)]
	struct Conversion<'a> {
	cvt: ConversionType,
	expr_to_cast: &'a Expr<'a>,
	to_type: Option<Symbol>,
	}

	/// The kind of conversion that is checked
	#[derive(Copy, Clone, Debug, PartialEq, Eq)]
	enum ConversionType {
	SignedToUnsigned,
	SignedToSigned,
	FromUnsigned,
	}

	/// Attempts to read either `<=` or `>=` with a normalized operand order.
	fn read_le_ge<'tcx>(
	op: BinOpKind,
	lhs: &'tcx Expr<'tcx>,
	rhs: &'tcx Expr<'tcx>,
	) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
	match op {
	BinOpKind::Le => Some((lhs, rhs)),
	BinOpKind::Ge => Some((rhs, lhs)),
	_ => None,
	}
	}

	impl<'a> Conversion<'a> {
	/// Combine multiple conversions if the are compatible
	pub fn combine(self, other: Self, cx: &LateContext<'_>) -> Option<Conversion<'a>> {
	if self.is_compatible(&other, cx) {
	// Prefer a Conversion that contains a type-constraint
	Some(if self.to_type.is_some() { self } else { other })
	} else {
	None
	}
	}

	/// Checks if two conversions are compatible
	/// same type of conversion, same 'castee' and same 'to type'
	pub fn is_compatible(&self, other: &Self, cx: &LateContext<'_>) -> bool {
	(self.cvt == other.cvt)
	&& (SpanlessEq::new(cx).eq_expr(self.expr_to_cast, other.expr_to_cast))
	&& (self.has_compatible_to_type(other))
	}

	/// Checks if the to-type is the same (if there is a type constraint)
	fn has_compatible_to_type(&self, other: &Self) -> bool {
	match (self.to_type, other.to_type) {
	(Some(l), Some(r)) => l == r,
	_ => true,
	}
	}

	/// Try to construct a new conversion if the conversion type is valid
	fn try_new(expr_to_cast: &'a Expr<'_>, from_type: Symbol, to_type: Symbol) -> Option<Conversion<'a>> {
	ConversionType::try_new(from_type, to_type).map(\|cvt\| Conversion {
	cvt,
	expr_to_cast,
	to_type: Some(to_type),
	})
	}

	/// Construct a new conversion without type constraint
	fn new_any(expr_to_cast: &'a Expr<'_>) -> Conversion<'a> {
	Conversion {
	cvt: ConversionType::SignedToUnsigned,
	expr_to_cast,
	to_type: None,
	}
	}
	}

	impl ConversionType {
	/// Creates a conversion type if the type is allowed & conversion is valid
	#[must_use]
	fn try_new(from: Symbol, to: Symbol) -> Option<Self> {
	if UINTS.contains(&from) {
	Some(Self::FromUnsigned)
	} else if SINTS.contains(&from) {
	if UINTS.contains(&to) {
	Some(Self::SignedToUnsigned)
	} else if SINTS.contains(&to) {
	Some(Self::SignedToSigned)
	} else {
	None
	}
	} else {
	None
	}
	}
	}

	/// Check for `expr <= (to_type::MAX as from_type)`
	fn check_upper_bound<'tcx>(lt: &'tcx Expr<'tcx>, gt: &'tcx Expr<'tcx>) -> Option<Conversion<'tcx>> {
	if let Some((from, to)) = get_types_from_cast(gt, INTS, sym::max_value, sym::MAX) {
	Conversion::try_new(lt, from, to)
	} else {
	None
	}
	}

	/// Check for `expr >= 0\|(to_type::MIN as from_type)`
	fn check_lower_bound<'tcx>(lt: &'tcx Expr<'tcx>, gt: &'tcx Expr<'tcx>) -> Option<Conversion<'tcx>> {
	check_lower_bound_zero(gt, lt).or_else(\|\| check_lower_bound_min(gt, lt))
	}

	/// Check for `expr >= 0`
	fn check_lower_bound_zero<'a>(candidate: &'a Expr<'_>, check: &'a Expr<'_>) -> Option<Conversion<'a>> {
	is_integer_literal(check, 0).then(\|\| Conversion::new_any(candidate))
	}

	/// Check for `expr >= (to_type::MIN as from_type)`
	fn check_lower_bound_min<'a>(candidate: &'a Expr<'_>, check: &'a Expr<'_>) -> Option<Conversion<'a>> {
	if let Some((from, to)) = get_types_from_cast(check, SINTS, sym::min_value, sym::MIN) {
	Conversion::try_new(candidate, from, to)
	} else {
	None
	}
	}

	/// Tries to extract the from- and to-type from a cast expression
	fn get_types_from_cast(
	expr: &Expr<'_>,
	types: &[Symbol],
	func: Symbol,
	assoc_const: Symbol,
	) -> Option<(Symbol, Symbol)> {
	// `to_type::max_value() as from_type`
	// or `to_type::MAX as from_type`
	let call_from_cast: Option<(&Expr<'_>, Symbol)> = if let ExprKind::Cast(limit, from_type) = &expr.kind
	// to_type::max_value(), from_type
	&& let TyKind::Path(from_type_path) = &from_type.kind
	&& let Some(from_sym) = int_ty_to_sym(from_type_path)
	{
	Some((limit, from_sym))
	} else {
	None
	};

	// `from_type::from(to_type::max_value())`
	let limit_from: Option<(&Expr<'_>, Symbol)> = call_from_cast.or_else(\|\| {
	if let ExprKind::Call(from_func, [limit]) = &expr.kind
	// `from_type::from, to_type::max_value()`
	// `from_type::from`
	&& let ExprKind::Path(path) = &from_func.kind
	&& let Some(from_sym) = get_implementing_type(path, INTS, sym::from)
	{
	Some((limit, from_sym))
	} else {
	None
	}
	});

	if let Some((limit, from_type)) = limit_from {
	match limit.kind {
	// `from_type::from(_)`
	ExprKind::Call(path, _) => {
	if let ExprKind::Path(ref path) = path.kind
	// `to_type`
	&& let Some(to_type) = get_implementing_type(path, types, func)
	{
	return Some((from_type, to_type));
	}
	},
	// `to_type::MAX`
	ExprKind::Path(ref path) => {
	if let Some(to_type) = get_implementing_type(path, types, assoc_const) {
	return Some((from_type, to_type));
	}
	},
	_ => {},
	}
	}
	None
	}

	/// Gets the type which implements the called function
	fn get_implementing_type(path: &QPath<'_>, candidates: &[Symbol], function: Symbol) -> Option<Symbol> {
	if let QPath::TypeRelative(ty, path) = &path
	&& path.ident.name == function
	&& let TyKind::Path(QPath::Resolved(None, tp)) = &ty.kind
	&& let [int] = tp.segments
	{
	candidates.iter().find(\|c\| int.ident.name == **c).copied()
	} else {
	None
	}
	}

	/// Gets the type as a string, if it is a supported integer
	fn int_ty_to_sym(path: &QPath<'_>) -> Option<Symbol> {
	if let QPath::Resolved(_, path) = *path
	&& let [ty] = path.segments
	{
	INTS.iter().find(\|c\| ty.ident.name == **c).copied()
	} else {
	None
	}
	}

	// Constants
	const UINTS: &[Symbol] = &[sym::u8, sym::u16, sym::u32, sym::u64, sym::usize];
	const SINTS: &[Symbol] = &[sym::i8, sym::i16, sym::i32, sym::i64, sym::isize];
	const INTS: &[Symbol] = &[
	sym::u8,
	sym::u16,
	sym::u32,
	sym::u64,
	sym::usize,
	sym::i8,
	sym::i16,
	sym::i32,
	sym::i64,
	sym::isize,
	];