| //! lint on manually implemented checked conversions that could be transformed into `try_from` |
| |
| use clippy_config::msrvs::{self, Msrv}; |
| use clippy_utils::diagnostics::span_lint_and_sugg; |
| use clippy_utils::source::snippet_with_applicability; |
| use clippy_utils::{in_constant, is_integer_literal, SpanlessEq}; |
| use if_chain::if_chain; |
| use rustc_errors::Applicability; |
| use rustc_hir::{BinOp, BinOpKind, Expr, ExprKind, QPath, TyKind}; |
| use rustc_lint::{LateContext, LateLintPass, LintContext}; |
| use rustc_middle::lint::in_external_macro; |
| use rustc_session::{declare_tool_lint, impl_lint_pass}; |
| |
| 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 { |
| #[must_use] |
| pub fn new(msrv: Msrv) -> Self { |
| Self { msrv } |
| } |
| } |
| |
| impl_lint_pass!(CheckedConversions => [CHECKED_CONVERSIONS]); |
| |
| impl<'tcx> LateLintPass<'tcx> for CheckedConversions { |
| fn check_expr(&mut self, cx: &LateContext<'_>, item: &Expr<'_>) { |
| if !self.msrv.meets(msrvs::TRY_FROM) { |
| return; |
| } |
| |
| let result = if_chain! { |
| if !in_constant(cx, item.hir_id); |
| if !in_external_macro(cx.sess(), item.span); |
| if let ExprKind::Binary(op, left, right) = &item.kind; |
| |
| then { |
| match op.node { |
| BinOpKind::Ge | BinOpKind::Le => single_check(item), |
| BinOpKind::And => double_check(cx, left, right), |
| _ => None, |
| } |
| } else { |
| None |
| } |
| }; |
| |
| if let Some(cv) = result { |
| if let Some(to_type) = cv.to_type { |
| 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, |
| ); |
| } |
| } |
| } |
| |
| extract_msrv_attr!(LateContext); |
| } |
| |
| /// Searches for a single check from unsigned to _ is done |
| /// todo: check for case signed -> larger unsigned == only x >= 0 |
| fn single_check<'tcx>(expr: &'tcx Expr<'tcx>) -> Option<Conversion<'tcx>> { |
| check_upper_bound(expr).filter(|cv| cv.cvt == ConversionType::FromUnsigned) |
| } |
| |
| /// Searches for a combination of upper & lower bound checks |
| fn double_check<'a>(cx: &LateContext<'_>, left: &'a Expr<'_>, right: &'a Expr<'_>) -> Option<Conversion<'a>> { |
| let upper_lower = |l, r| { |
| let upper = check_upper_bound(l); |
| let lower = check_lower_bound(r); |
| |
| upper.zip(lower).and_then(|(l, r)| l.combine(r, cx)) |
| }; |
| |
| upper_lower(left, right).or_else(|| upper_lower(right, left)) |
| } |
| |
| /// 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<&'a str>, |
| } |
| |
| /// The kind of conversion that is checked |
| #[derive(Copy, Clone, Debug, PartialEq, Eq)] |
| enum ConversionType { |
| SignedToUnsigned, |
| SignedToSigned, |
| FromUnsigned, |
| } |
| |
| 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: &str, to_type: &'a str) -> 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: &str, to: &str) -> 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>(expr: &'tcx Expr<'tcx>) -> Option<Conversion<'tcx>> { |
| if_chain! { |
| if let ExprKind::Binary(ref op, left, right) = &expr.kind; |
| if let Some((candidate, check)) = normalize_le_ge(op, left, right); |
| if let Some((from, to)) = get_types_from_cast(check, INTS, "max_value", "MAX"); |
| |
| then { |
| Conversion::try_new(candidate, from, to) |
| } else { |
| None |
| } |
| } |
| } |
| |
| /// Check for `expr >= 0|(to_type::MIN as from_type)` |
| fn check_lower_bound<'tcx>(expr: &'tcx Expr<'tcx>) -> Option<Conversion<'tcx>> { |
| fn check_function<'a>(candidate: &'a Expr<'a>, check: &'a Expr<'a>) -> Option<Conversion<'a>> { |
| (check_lower_bound_zero(candidate, check)).or_else(|| (check_lower_bound_min(candidate, check))) |
| } |
| |
| // First of we need a binary containing the expression & the cast |
| if let ExprKind::Binary(ref op, left, right) = &expr.kind { |
| normalize_le_ge(op, right, left).and_then(|(l, r)| check_function(l, r)) |
| } else { |
| None |
| } |
| } |
| |
| /// 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, "min_value", "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<'a>( |
| expr: &'a Expr<'_>, |
| types: &'a [&str], |
| func: &'a str, |
| assoc_const: &'a str, |
| ) -> Option<(&'a str, &'a str)> { |
| // `to_type::max_value() as from_type` |
| // or `to_type::MAX as from_type` |
| let call_from_cast: Option<(&Expr<'_>, &str)> = if_chain! { |
| // to_type::max_value(), from_type |
| if let ExprKind::Cast(limit, from_type) = &expr.kind; |
| if let TyKind::Path(ref from_type_path) = &from_type.kind; |
| if let Some(from_sym) = int_ty_to_sym(from_type_path); |
| |
| then { |
| Some((limit, from_sym)) |
| } else { |
| None |
| } |
| }; |
| |
| // `from_type::from(to_type::max_value())` |
| let limit_from: Option<(&Expr<'_>, &str)> = call_from_cast.or_else(|| { |
| if_chain! { |
| // `from_type::from, to_type::max_value()` |
| if let ExprKind::Call(from_func, [limit]) = &expr.kind; |
| // `from_type::from` |
| if let ExprKind::Path(ref path) = &from_func.kind; |
| if let Some(from_sym) = get_implementing_type(path, INTS, "from"); |
| |
| then { |
| 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` |
| if 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<'a>(path: &QPath<'_>, candidates: &'a [&str], function: &str) -> Option<&'a str> { |
| if_chain! { |
| if let QPath::TypeRelative(ty, path) = &path; |
| if path.ident.name.as_str() == function; |
| if let TyKind::Path(QPath::Resolved(None, tp)) = &ty.kind; |
| if let [int] = tp.segments; |
| then { |
| let name = int.ident.name.as_str(); |
| candidates.iter().find(|c| &name == *c).copied() |
| } else { |
| None |
| } |
| } |
| } |
| |
| /// Gets the type as a string, if it is a supported integer |
| fn int_ty_to_sym<'tcx>(path: &QPath<'_>) -> Option<&'tcx str> { |
| if_chain! { |
| if let QPath::Resolved(_, path) = *path; |
| if let [ty] = path.segments; |
| then { |
| let name = ty.ident.name.as_str(); |
| INTS.iter().find(|c| &name == *c).copied() |
| } else { |
| None |
| } |
| } |
| } |
| |
| /// Will return the expressions as if they were expr1 <= expr2 |
| fn normalize_le_ge<'a>(op: &BinOp, left: &'a Expr<'a>, right: &'a Expr<'a>) -> Option<(&'a Expr<'a>, &'a Expr<'a>)> { |
| match op.node { |
| BinOpKind::Le => Some((left, right)), |
| BinOpKind::Ge => Some((right, left)), |
| _ => None, |
| } |
| } |
| |
| // Constants |
| const UINTS: &[&str] = &["u8", "u16", "u32", "u64", "usize"]; |
| const SINTS: &[&str] = &["i8", "i16", "i32", "i64", "isize"]; |
| const INTS: &[&str] = &["u8", "u16", "u32", "u64", "usize", "i8", "i16", "i32", "i64", "isize"]; |