| use reexport::*; |
| use rustc::hir::*; |
| use rustc::hir::intravisit::{FnKind, Visitor, walk_ty}; |
| use rustc::lint::*; |
| use rustc::ty; |
| use std::cmp::Ordering; |
| use syntax::ast::{IntTy, UintTy, FloatTy}; |
| use syntax::codemap::Span; |
| use utils::{comparisons, higher, in_external_macro, in_macro, match_def_path, snippet, |
| span_help_and_lint, span_lint}; |
| use utils::paths; |
| |
| /// Handles all the linting of funky types |
| #[allow(missing_copy_implementations)] |
| pub struct TypePass; |
| |
| /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code. |
| /// |
| /// **Why is this bad?** `Vec` already keeps its contents in a separate area on |
| /// the heap. So if you `Box` it, you just add another level of indirection |
| /// without any benefit whatsoever. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// struct X { |
| /// values: Box<Vec<Foo>>, |
| /// } |
| /// ``` |
| declare_lint! { |
| pub BOX_VEC, |
| Warn, |
| "usage of `Box<Vec<T>>`, vector elements are already on the heap" |
| } |
| |
| /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a |
| /// `Vec` or a `VecDeque` (formerly called `RingBuf`). |
| /// |
| /// **Why is this bad?** Gankro says: |
| /// |
| /// > The TL;DR of `LinkedList` is that it's built on a massive amount of pointers and indirection. |
| /// > It wastes memory, it has terrible cache locality, and is all-around slow. `RingBuf`, while |
| /// > "only" amortized for push/pop, should be faster in the general case for almost every possible |
| /// > workload, and isn't even amortized at all if you can predict the capacity you need. |
| /// > |
| /// > `LinkedList`s are only really good if you're doing a lot of merging or splitting of lists. |
| /// > This is because they can just mangle some pointers instead of actually copying the data. Even |
| /// > if you're doing a lot of insertion in the middle of the list, `RingBuf` can still be better |
| /// > because of how expensive it is to seek to the middle of a `LinkedList`. |
| /// |
| /// **Known problems:** False positives – the instances where using a |
| /// `LinkedList` makes sense are few and far between, but they can still happen. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let x = LinkedList::new(); |
| /// ``` |
| declare_lint! { |
| pub LINKEDLIST, |
| Warn, |
| "usage of LinkedList, usually a vector is faster, or a more specialized data \ |
| structure like a VecDeque" |
| } |
| |
| impl LintPass for TypePass { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(BOX_VEC, LINKEDLIST) |
| } |
| } |
| |
| impl LateLintPass for TypePass { |
| fn check_ty(&mut self, cx: &LateContext, ast_ty: &Ty) { |
| if in_macro(cx, ast_ty.span) { |
| return; |
| } |
| if let Some(did) = cx.tcx.def_map.borrow().get(&ast_ty.id) { |
| if let def::Def::Struct(..) = did.full_def() { |
| if Some(did.full_def().def_id()) == cx.tcx.lang_items.owned_box() { |
| if_let_chain! {[ |
| let TyPath(_, ref path) = ast_ty.node, |
| let Some(ref last) = path.segments.last(), |
| let PathParameters::AngleBracketedParameters(ref ag) = last.parameters, |
| let Some(ref vec) = ag.types.get(0), |
| let Some(did) = cx.tcx.def_map.borrow().get(&vec.id), |
| let def::Def::Struct(..) = did.full_def(), |
| match_def_path(cx, did.full_def().def_id(), &paths::VEC), |
| ], { |
| span_help_and_lint(cx, |
| BOX_VEC, |
| ast_ty.span, |
| "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`", |
| "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation."); |
| }} |
| } else if match_def_path(cx, did.full_def().def_id(), &paths::LINKED_LIST) { |
| span_help_and_lint(cx, |
| LINKEDLIST, |
| ast_ty.span, |
| "I see you're using a LinkedList! Perhaps you meant some other data structure?", |
| "a VecDeque might work"); |
| } |
| } |
| } |
| } |
| } |
| |
| #[allow(missing_copy_implementations)] |
| pub struct LetPass; |
| |
| /// **What it does:** Checks for binding a unit value. |
| /// |
| /// **Why is this bad?** A unit value cannot usefully be used anywhere. So |
| /// binding one is kind of pointless. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let x = { 1; }; |
| /// ``` |
| declare_lint! { |
| pub LET_UNIT_VALUE, |
| Warn, |
| "creating a let binding to a value of unit type, which usually can't be used afterwards" |
| } |
| |
| fn check_let_unit(cx: &LateContext, decl: &Decl) { |
| if let DeclLocal(ref local) = decl.node { |
| let bindtype = &cx.tcx.tables().pat_ty(&local.pat).sty; |
| match *bindtype { |
| ty::TyTuple(slice) if slice.is_empty() => { |
| if in_external_macro(cx, decl.span) || in_macro(cx, local.pat.span) { |
| return; |
| } |
| if higher::is_from_for_desugar(decl) { |
| return; |
| } |
| span_lint(cx, |
| LET_UNIT_VALUE, |
| decl.span, |
| &format!("this let-binding has unit value. Consider omitting `let {} =`", |
| snippet(cx, local.pat.span, ".."))); |
| } |
| _ => (), |
| } |
| } |
| } |
| |
| impl LintPass for LetPass { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(LET_UNIT_VALUE) |
| } |
| } |
| |
| impl LateLintPass for LetPass { |
| fn check_decl(&mut self, cx: &LateContext, decl: &Decl) { |
| check_let_unit(cx, decl) |
| } |
| } |
| |
| /// **What it does:** Checks for comparisons to unit. |
| /// |
| /// **Why is this bad?** Unit is always equal to itself, and thus is just a |
| /// clumsily written constant. Mostly this happens when someone accidentally |
| /// adds semicolons at the end of the operands. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// if { foo(); } == { bar(); } { baz(); } |
| /// ``` |
| /// is equal to |
| /// ```rust |
| /// { foo(); bar(); baz(); } |
| /// ``` |
| declare_lint! { |
| pub UNIT_CMP, |
| Warn, |
| "comparing unit values" |
| } |
| |
| #[allow(missing_copy_implementations)] |
| pub struct UnitCmp; |
| |
| impl LintPass for UnitCmp { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(UNIT_CMP) |
| } |
| } |
| |
| impl LateLintPass for UnitCmp { |
| fn check_expr(&mut self, cx: &LateContext, expr: &Expr) { |
| if in_macro(cx, expr.span) { |
| return; |
| } |
| if let ExprBinary(ref cmp, ref left, _) = expr.node { |
| let op = cmp.node; |
| if op.is_comparison() { |
| let sty = &cx.tcx.tables().expr_ty(left).sty; |
| match *sty { |
| ty::TyTuple(slice) if slice.is_empty() => { |
| let result = match op { |
| BiEq | BiLe | BiGe => "true", |
| _ => "false", |
| }; |
| span_lint(cx, |
| UNIT_CMP, |
| expr.span, |
| &format!("{}-comparison of unit values detected. This will always be {}", |
| op.as_str(), |
| result)); |
| } |
| _ => () |
| } |
| } |
| } |
| } |
| } |
| |
| pub struct CastPass; |
| |
| /// **What it does:** Checks for casts from any numerical to a float type where |
| /// the receiving type cannot store all values from the original type without |
| /// rounding errors. This possible rounding is to be expected, so this lint is |
| /// `Allow` by default. |
| /// |
| /// Basically, this warns on casting any integer with 32 or more bits to `f32` |
| /// or any 64-bit integer to `f64`. |
| /// |
| /// **Why is this bad?** It's not bad at all. But in some applications it can be |
| /// helpful to know where precision loss can take place. This lint can help find |
| /// those places in the code. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let x = u64::MAX; x as f64 |
| /// ``` |
| declare_lint! { |
| pub CAST_PRECISION_LOSS, |
| Allow, |
| "casts that cause loss of precision, e.g `x as f32` where `x: u64`" |
| } |
| |
| /// **What it does:** Checks for casts from a signed to an unsigned numerical |
| /// type. In this case, negative values wrap around to large positive values, |
| /// which can be quite surprising in practice. However, as the cast works as |
| /// defined, this lint is `Allow` by default. |
| /// |
| /// **Why is this bad?** Possibly surprising results. You can activate this lint |
| /// as a one-time check to see where numerical wrapping can arise. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let y: i8 = -1; |
| /// y as u64 // will return 18446744073709551615 |
| /// ``` |
| declare_lint! { |
| pub CAST_SIGN_LOSS, |
| Allow, |
| "casts from signed types to unsigned types, e.g `x as u32` where `x: i32`" |
| } |
| |
| /// **What it does:** Checks for on casts between numerical types that may |
| /// truncate large values. This is expected behavior, so the cast is `Allow` by |
| /// default. |
| /// |
| /// **Why is this bad?** In some problem domains, it is good practice to avoid |
| /// truncation. This lint can be activated to help assess where additional |
| /// checks could be beneficial. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// fn as_u8(x: u64) -> u8 { x as u8 } |
| /// ``` |
| declare_lint! { |
| pub CAST_POSSIBLE_TRUNCATION, |
| Allow, |
| "casts that may cause truncation of the value, e.g `x as u8` where `x: u32`, \ |
| or `x as i32` where `x: f32`" |
| } |
| |
| /// **What it does:** Checks for casts from an unsigned type to a signed type of |
| /// the same size. Performing such a cast is a 'no-op' for the compiler, |
| /// i.e. nothing is changed at the bit level, and the binary representation of |
| /// the value is reinterpreted. This can cause wrapping if the value is too big |
| /// for the target signed type. However, the cast works as defined, so this lint |
| /// is `Allow` by default. |
| /// |
| /// **Why is this bad?** While such a cast is not bad in itself, the results can |
| /// be surprising when this is not the intended behavior, as demonstrated by the |
| /// example below. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// u32::MAX as i32 // will yield a value of `-1` |
| /// ``` |
| declare_lint! { |
| pub CAST_POSSIBLE_WRAP, |
| Allow, |
| "casts that may cause wrapping around the value, e.g `x as i32` where `x: u32` \ |
| and `x > i32::MAX`" |
| } |
| |
| /// Returns the size in bits of an integral type. |
| /// Will return 0 if the type is not an int or uint variant |
| fn int_ty_to_nbits(typ: &ty::TyS) -> usize { |
| let n = match typ.sty { |
| ty::TyInt(i) => 4 << (i as usize), |
| ty::TyUint(u) => 4 << (u as usize), |
| _ => 0, |
| }; |
| // n == 4 is the usize/isize case |
| if n == 4 { |
| ::std::mem::size_of::<usize>() * 8 |
| } else { |
| n |
| } |
| } |
| |
| fn is_isize_or_usize(typ: &ty::TyS) -> bool { |
| match typ.sty { |
| ty::TyInt(IntTy::Is) | |
| ty::TyUint(UintTy::Us) => true, |
| _ => false, |
| } |
| } |
| |
| fn span_precision_loss_lint(cx: &LateContext, expr: &Expr, cast_from: &ty::TyS, cast_to_f64: bool) { |
| let mantissa_nbits = if cast_to_f64 { |
| 52 |
| } else { |
| 23 |
| }; |
| let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64; |
| let arch_dependent_str = "on targets with 64-bit wide pointers "; |
| let from_nbits_str = if arch_dependent { |
| "64".to_owned() |
| } else if is_isize_or_usize(cast_from) { |
| "32 or 64".to_owned() |
| } else { |
| int_ty_to_nbits(cast_from).to_string() |
| }; |
| span_lint(cx, |
| CAST_PRECISION_LOSS, |
| expr.span, |
| &format!("casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \ |
| is only {4} bits wide)", |
| cast_from, |
| if cast_to_f64 { |
| "f64" |
| } else { |
| "f32" |
| }, |
| if arch_dependent { |
| arch_dependent_str |
| } else { |
| "" |
| }, |
| from_nbits_str, |
| mantissa_nbits)); |
| } |
| |
| enum ArchSuffix { |
| _32, |
| _64, |
| None, |
| } |
| |
| fn check_truncation_and_wrapping(cx: &LateContext, expr: &Expr, cast_from: &ty::TyS, cast_to: &ty::TyS) { |
| let arch_64_suffix = " on targets with 64-bit wide pointers"; |
| let arch_32_suffix = " on targets with 32-bit wide pointers"; |
| let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed(); |
| let (from_nbits, to_nbits) = (int_ty_to_nbits(cast_from), int_ty_to_nbits(cast_to)); |
| let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) = match (is_isize_or_usize(cast_from), |
| is_isize_or_usize(cast_to)) { |
| (true, true) | (false, false) => { |
| (to_nbits < from_nbits, |
| ArchSuffix::None, |
| to_nbits == from_nbits && cast_unsigned_to_signed, |
| ArchSuffix::None) |
| } |
| (true, false) => { |
| (to_nbits <= 32, |
| if to_nbits == 32 { |
| ArchSuffix::_64 |
| } else { |
| ArchSuffix::None |
| }, |
| to_nbits <= 32 && cast_unsigned_to_signed, |
| ArchSuffix::_32) |
| } |
| (false, true) => { |
| (from_nbits == 64, |
| ArchSuffix::_32, |
| cast_unsigned_to_signed, |
| if from_nbits == 64 { |
| ArchSuffix::_64 |
| } else { |
| ArchSuffix::_32 |
| }) |
| } |
| }; |
| if span_truncation { |
| span_lint(cx, |
| CAST_POSSIBLE_TRUNCATION, |
| expr.span, |
| &format!("casting {} to {} may truncate the value{}", |
| cast_from, |
| cast_to, |
| match suffix_truncation { |
| ArchSuffix::_32 => arch_32_suffix, |
| ArchSuffix::_64 => arch_64_suffix, |
| ArchSuffix::None => "", |
| })); |
| } |
| if span_wrap { |
| span_lint(cx, |
| CAST_POSSIBLE_WRAP, |
| expr.span, |
| &format!("casting {} to {} may wrap around the value{}", |
| cast_from, |
| cast_to, |
| match suffix_wrap { |
| ArchSuffix::_32 => arch_32_suffix, |
| ArchSuffix::_64 => arch_64_suffix, |
| ArchSuffix::None => "", |
| })); |
| } |
| } |
| |
| impl LintPass for CastPass { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(CAST_PRECISION_LOSS, |
| CAST_SIGN_LOSS, |
| CAST_POSSIBLE_TRUNCATION, |
| CAST_POSSIBLE_WRAP) |
| } |
| } |
| |
| impl LateLintPass for CastPass { |
| fn check_expr(&mut self, cx: &LateContext, expr: &Expr) { |
| if let ExprCast(ref ex, _) = expr.node { |
| let (cast_from, cast_to) = (cx.tcx.tables().expr_ty(ex), cx.tcx.tables().expr_ty(expr)); |
| if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx, expr.span) { |
| match (cast_from.is_integral(), cast_to.is_integral()) { |
| (true, false) => { |
| let from_nbits = int_ty_to_nbits(cast_from); |
| let to_nbits = if let ty::TyFloat(FloatTy::F32) = cast_to.sty { |
| 32 |
| } else { |
| 64 |
| }; |
| if is_isize_or_usize(cast_from) || from_nbits >= to_nbits { |
| span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64); |
| } |
| } |
| (false, true) => { |
| span_lint(cx, |
| CAST_POSSIBLE_TRUNCATION, |
| expr.span, |
| &format!("casting {} to {} may truncate the value", cast_from, cast_to)); |
| if !cast_to.is_signed() { |
| span_lint(cx, |
| CAST_SIGN_LOSS, |
| expr.span, |
| &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to)); |
| } |
| } |
| (true, true) => { |
| if cast_from.is_signed() && !cast_to.is_signed() { |
| span_lint(cx, |
| CAST_SIGN_LOSS, |
| expr.span, |
| &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to)); |
| } |
| check_truncation_and_wrapping(cx, expr, cast_from, cast_to); |
| } |
| (false, false) => { |
| if let (&ty::TyFloat(FloatTy::F64), &ty::TyFloat(FloatTy::F32)) = (&cast_from.sty, |
| &cast_to.sty) { |
| span_lint(cx, |
| CAST_POSSIBLE_TRUNCATION, |
| expr.span, |
| "casting f64 to f32 may truncate the value"); |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| /// **What it does:** Checks for types used in structs, parameters and `let` |
| /// declarations above a certain complexity threshold. |
| /// |
| /// **Why is this bad?** Too complex types make the code less readable. Consider |
| /// using a `type` definition to simplify them. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// struct Foo { inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>> } |
| /// ``` |
| declare_lint! { |
| pub TYPE_COMPLEXITY, |
| Warn, |
| "usage of very complex types that might be better factored into `type` definitions" |
| } |
| |
| #[allow(missing_copy_implementations)] |
| pub struct TypeComplexityPass { |
| threshold: u64, |
| } |
| |
| impl TypeComplexityPass { |
| pub fn new(threshold: u64) -> Self { |
| TypeComplexityPass { threshold: threshold } |
| } |
| } |
| |
| impl LintPass for TypeComplexityPass { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(TYPE_COMPLEXITY) |
| } |
| } |
| |
| impl LateLintPass for TypeComplexityPass { |
| fn check_fn(&mut self, cx: &LateContext, _: FnKind, decl: &FnDecl, _: &Expr, _: Span, _: NodeId) { |
| self.check_fndecl(cx, decl); |
| } |
| |
| fn check_struct_field(&mut self, cx: &LateContext, field: &StructField) { |
| // enum variants are also struct fields now |
| self.check_type(cx, &field.ty); |
| } |
| |
| fn check_item(&mut self, cx: &LateContext, item: &Item) { |
| match item.node { |
| ItemStatic(ref ty, _, _) | |
| ItemConst(ref ty, _) => self.check_type(cx, ty), |
| // functions, enums, structs, impls and traits are covered |
| _ => (), |
| } |
| } |
| |
| fn check_trait_item(&mut self, cx: &LateContext, item: &TraitItem) { |
| match item.node { |
| ConstTraitItem(ref ty, _) | |
| TypeTraitItem(_, Some(ref ty)) => self.check_type(cx, ty), |
| MethodTraitItem(MethodSig { ref decl, .. }, None) => self.check_fndecl(cx, decl), |
| // methods with default impl are covered by check_fn |
| _ => (), |
| } |
| } |
| |
| fn check_impl_item(&mut self, cx: &LateContext, item: &ImplItem) { |
| match item.node { |
| ImplItemKind::Const(ref ty, _) | |
| ImplItemKind::Type(ref ty) => self.check_type(cx, ty), |
| // methods are covered by check_fn |
| _ => (), |
| } |
| } |
| |
| fn check_local(&mut self, cx: &LateContext, local: &Local) { |
| if let Some(ref ty) = local.ty { |
| self.check_type(cx, ty); |
| } |
| } |
| } |
| |
| impl TypeComplexityPass { |
| fn check_fndecl(&self, cx: &LateContext, decl: &FnDecl) { |
| for arg in &decl.inputs { |
| self.check_type(cx, &arg.ty); |
| } |
| if let Return(ref ty) = decl.output { |
| self.check_type(cx, ty); |
| } |
| } |
| |
| fn check_type(&self, cx: &LateContext, ty: &Ty) { |
| if in_macro(cx, ty.span) { |
| return; |
| } |
| let score = { |
| let mut visitor = TypeComplexityVisitor { |
| score: 0, |
| nest: 1, |
| }; |
| visitor.visit_ty(ty); |
| visitor.score |
| }; |
| |
| if score > self.threshold { |
| span_lint(cx, |
| TYPE_COMPLEXITY, |
| ty.span, |
| "very complex type used. Consider factoring parts into `type` definitions"); |
| } |
| } |
| } |
| |
| /// Walks a type and assigns a complexity score to it. |
| struct TypeComplexityVisitor { |
| /// total complexity score of the type |
| score: u64, |
| /// current nesting level |
| nest: u64, |
| } |
| |
| impl<'v> Visitor<'v> for TypeComplexityVisitor { |
| fn visit_ty(&mut self, ty: &'v Ty) { |
| let (add_score, sub_nest) = match ty.node { |
| // _, &x and *x have only small overhead; don't mess with nesting level |
| TyInfer | TyPtr(..) | TyRptr(..) => (1, 0), |
| |
| // the "normal" components of a type: named types, arrays/tuples |
| TyPath(..) | |
| TySlice(..) | |
| TyTup(..) | |
| TyArray(..) => (10 * self.nest, 1), |
| |
| // "Sum" of trait bounds |
| TyObjectSum(..) => (20 * self.nest, 0), |
| |
| // function types and "for<...>" bring a lot of overhead |
| TyBareFn(..) | |
| TyPolyTraitRef(..) => (50 * self.nest, 1), |
| |
| _ => (0, 0), |
| }; |
| self.score += add_score; |
| self.nest += sub_nest; |
| walk_ty(self, ty); |
| self.nest -= sub_nest; |
| } |
| } |
| |
| /// **What it does:** Checks for expressions where a character literal is cast |
| /// to `u8` and suggests using a byte literal instead. |
| /// |
| /// **Why is this bad?** In general, casting values to smaller types is |
| /// error-prone and should be avoided where possible. In the particular case of |
| /// converting a character literal to u8, it is easy to avoid by just using a |
| /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter |
| /// than `'a' as u8`. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// 'x' as u8 |
| /// ``` |
| declare_lint! { |
| pub CHAR_LIT_AS_U8, |
| Warn, |
| "casting a character literal to u8" |
| } |
| |
| pub struct CharLitAsU8; |
| |
| impl LintPass for CharLitAsU8 { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(CHAR_LIT_AS_U8) |
| } |
| } |
| |
| impl LateLintPass for CharLitAsU8 { |
| fn check_expr(&mut self, cx: &LateContext, expr: &Expr) { |
| use syntax::ast::{LitKind, UintTy}; |
| |
| if let ExprCast(ref e, _) = expr.node { |
| if let ExprLit(ref l) = e.node { |
| if let LitKind::Char(_) = l.node { |
| if ty::TyUint(UintTy::U8) == cx.tcx.tables().expr_ty(expr).sty && !in_macro(cx, expr.span) { |
| let msg = "casting character literal to u8. `char`s \ |
| are 4 bytes wide in rust, so casting to u8 \ |
| truncates them"; |
| let help = format!("Consider using a byte literal \ |
| instead:\nb{}", |
| snippet(cx, e.span, "'x'")); |
| span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help); |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| /// **What it does:** Checks for comparisons where one side of the relation is |
| /// either the minimum or maximum value for its type and warns if it involves a |
| /// case that is always true or always false. Only integer and boolean types are |
| /// checked. |
| /// |
| /// **Why is this bad?** An expression like `min <= x` may misleadingly imply |
| /// that is is possible for `x` to be less than the minimum. Expressions like |
| /// `max < x` are probably mistakes. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// vec.len() <= 0 |
| /// 100 > std::i32::MAX |
| /// ``` |
| declare_lint! { |
| pub ABSURD_EXTREME_COMPARISONS, |
| Warn, |
| "a comparison with a maximum or minimum value that is always true or false" |
| } |
| |
| pub struct AbsurdExtremeComparisons; |
| |
| impl LintPass for AbsurdExtremeComparisons { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(ABSURD_EXTREME_COMPARISONS) |
| } |
| } |
| |
| enum ExtremeType { |
| Minimum, |
| Maximum, |
| } |
| |
| struct ExtremeExpr<'a> { |
| which: ExtremeType, |
| expr: &'a Expr, |
| } |
| |
| enum AbsurdComparisonResult { |
| AlwaysFalse, |
| AlwaysTrue, |
| InequalityImpossible, |
| } |
| |
| |
| |
| fn detect_absurd_comparison<'a>(cx: &LateContext, op: BinOp_, lhs: &'a Expr, rhs: &'a Expr) |
| -> Option<(ExtremeExpr<'a>, AbsurdComparisonResult)> { |
| use types::ExtremeType::*; |
| use types::AbsurdComparisonResult::*; |
| use utils::comparisons::*; |
| type Extr<'a> = ExtremeExpr<'a>; |
| |
| let normalized = normalize_comparison(op, lhs, rhs); |
| let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized { |
| val |
| } else { |
| return None; |
| }; |
| |
| let lx = detect_extreme_expr(cx, normalized_lhs); |
| let rx = detect_extreme_expr(cx, normalized_rhs); |
| |
| Some(match rel { |
| Rel::Lt => { |
| match (lx, rx) { |
| (Some(l @ Extr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x |
| (_, Some(r @ Extr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min |
| _ => return None, |
| } |
| } |
| Rel::Le => { |
| match (lx, rx) { |
| (Some(l @ Extr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x |
| (Some(l @ Extr { which: Maximum, .. }), _) => (l, InequalityImpossible), //max <= x |
| (_, Some(r @ Extr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min |
| (_, Some(r @ Extr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max |
| _ => return None, |
| } |
| } |
| Rel::Ne | Rel::Eq => return None, |
| }) |
| } |
| |
| fn detect_extreme_expr<'a>(cx: &LateContext, expr: &'a Expr) -> Option<ExtremeExpr<'a>> { |
| use rustc::middle::const_val::ConstVal::*; |
| use rustc_const_math::*; |
| use rustc_const_eval::EvalHint::ExprTypeChecked; |
| use rustc_const_eval::*; |
| use types::ExtremeType::*; |
| |
| let ty = &cx.tcx.tables().expr_ty(expr).sty; |
| |
| match *ty { |
| ty::TyBool | ty::TyInt(_) | ty::TyUint(_) => (), |
| _ => return None, |
| }; |
| |
| let cv = match eval_const_expr_partial(cx.tcx, expr, ExprTypeChecked, None) { |
| Ok(val) => val, |
| Err(_) => return None, |
| }; |
| |
| let which = match (ty, cv) { |
| (&ty::TyBool, Bool(false)) | |
| (&ty::TyInt(IntTy::Is), Integral(Isize(Is32(::std::i32::MIN)))) | |
| (&ty::TyInt(IntTy::Is), Integral(Isize(Is64(::std::i64::MIN)))) | |
| (&ty::TyInt(IntTy::I8), Integral(I8(::std::i8::MIN))) | |
| (&ty::TyInt(IntTy::I16), Integral(I16(::std::i16::MIN))) | |
| (&ty::TyInt(IntTy::I32), Integral(I32(::std::i32::MIN))) | |
| (&ty::TyInt(IntTy::I64), Integral(I64(::std::i64::MIN))) | |
| (&ty::TyUint(UintTy::Us), Integral(Usize(Us32(::std::u32::MIN)))) | |
| (&ty::TyUint(UintTy::Us), Integral(Usize(Us64(::std::u64::MIN)))) | |
| (&ty::TyUint(UintTy::U8), Integral(U8(::std::u8::MIN))) | |
| (&ty::TyUint(UintTy::U16), Integral(U16(::std::u16::MIN))) | |
| (&ty::TyUint(UintTy::U32), Integral(U32(::std::u32::MIN))) | |
| (&ty::TyUint(UintTy::U64), Integral(U64(::std::u64::MIN))) => Minimum, |
| |
| (&ty::TyBool, Bool(true)) | |
| (&ty::TyInt(IntTy::Is), Integral(Isize(Is32(::std::i32::MAX)))) | |
| (&ty::TyInt(IntTy::Is), Integral(Isize(Is64(::std::i64::MAX)))) | |
| (&ty::TyInt(IntTy::I8), Integral(I8(::std::i8::MAX))) | |
| (&ty::TyInt(IntTy::I16), Integral(I16(::std::i16::MAX))) | |
| (&ty::TyInt(IntTy::I32), Integral(I32(::std::i32::MAX))) | |
| (&ty::TyInt(IntTy::I64), Integral(I64(::std::i64::MAX))) | |
| (&ty::TyUint(UintTy::Us), Integral(Usize(Us32(::std::u32::MAX)))) | |
| (&ty::TyUint(UintTy::Us), Integral(Usize(Us64(::std::u64::MAX)))) | |
| (&ty::TyUint(UintTy::U8), Integral(U8(::std::u8::MAX))) | |
| (&ty::TyUint(UintTy::U16), Integral(U16(::std::u16::MAX))) | |
| (&ty::TyUint(UintTy::U32), Integral(U32(::std::u32::MAX))) | |
| (&ty::TyUint(UintTy::U64), Integral(U64(::std::u64::MAX))) => Maximum, |
| |
| _ => return None, |
| }; |
| Some(ExtremeExpr { |
| which: which, |
| expr: expr, |
| }) |
| } |
| |
| impl LateLintPass for AbsurdExtremeComparisons { |
| fn check_expr(&mut self, cx: &LateContext, expr: &Expr) { |
| use types::ExtremeType::*; |
| use types::AbsurdComparisonResult::*; |
| |
| if let ExprBinary(ref cmp, ref lhs, ref rhs) = expr.node { |
| if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) { |
| if !in_macro(cx, expr.span) { |
| let msg = "this comparison involving the minimum or maximum element for this \ |
| type contains a case that is always true or always false"; |
| |
| let conclusion = match result { |
| AlwaysFalse => "this comparison is always false".to_owned(), |
| AlwaysTrue => "this comparison is always true".to_owned(), |
| InequalityImpossible => { |
| format!("the case where the two sides are not equal never occurs, consider using {} == {} \ |
| instead", |
| snippet(cx, lhs.span, "lhs"), |
| snippet(cx, rhs.span, "rhs")) |
| } |
| }; |
| |
| let help = format!("because {} is the {} value for this type, {}", |
| snippet(cx, culprit.expr.span, "x"), |
| match culprit.which { |
| Minimum => "minimum", |
| Maximum => "maximum", |
| }, |
| conclusion); |
| |
| span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help); |
| } |
| } |
| } |
| } |
| } |
| |
| /// **What it does:** Checks for comparisons where the relation is always either |
| /// true or false, but where one side has been upcast so that the comparison is |
| /// necessary. Only integer types are checked. |
| /// |
| /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300` |
| /// will mistakenly imply that it is possible for `x` to be outside the range of |
| /// `u8`. |
| /// |
| /// **Known problems:** https://github.com/Manishearth/rust-clippy/issues/886 |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let x : u8 = ...; (x as u32) > 300 |
| /// ``` |
| declare_lint! { |
| pub INVALID_UPCAST_COMPARISONS, |
| Allow, |
| "a comparison involving an upcast which is always true or false" |
| } |
| |
| pub struct InvalidUpcastComparisons; |
| |
| impl LintPass for InvalidUpcastComparisons { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(INVALID_UPCAST_COMPARISONS) |
| } |
| } |
| |
| #[derive(Copy, Clone, Debug, Eq)] |
| enum FullInt { |
| S(i64), |
| U(u64), |
| } |
| |
| impl FullInt { |
| #[allow(cast_sign_loss)] |
| fn cmp_s_u(s: i64, u: u64) -> Ordering { |
| if s < 0 { |
| Ordering::Less |
| } else if u > (i64::max_value() as u64) { |
| Ordering::Greater |
| } else { |
| (s as u64).cmp(&u) |
| } |
| } |
| } |
| |
| impl PartialEq for FullInt { |
| fn eq(&self, other: &Self) -> bool { |
| self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal |
| } |
| } |
| |
| impl PartialOrd for FullInt { |
| fn partial_cmp(&self, other: &Self) -> Option<Ordering> { |
| Some(match (self, other) { |
| (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o), |
| (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o), |
| (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o), |
| (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(), |
| }) |
| } |
| } |
| impl Ord for FullInt { |
| fn cmp(&self, other: &Self) -> Ordering { |
| self.partial_cmp(other).expect("partial_cmp for FullInt can never return None") |
| } |
| } |
| |
| |
| fn numeric_cast_precast_bounds<'a>(cx: &LateContext, expr: &'a Expr) -> Option<(FullInt, FullInt)> { |
| use rustc::ty::TypeVariants::{TyInt, TyUint}; |
| use syntax::ast::{IntTy, UintTy}; |
| use std::*; |
| |
| if let ExprCast(ref cast_exp, _) = expr.node { |
| match cx.tcx.tables().expr_ty(cast_exp).sty { |
| TyInt(int_ty) => { |
| Some(match int_ty { |
| IntTy::I8 => (FullInt::S(i8::min_value() as i64), FullInt::S(i8::max_value() as i64)), |
| IntTy::I16 => (FullInt::S(i16::min_value() as i64), FullInt::S(i16::max_value() as i64)), |
| IntTy::I32 => (FullInt::S(i32::min_value() as i64), FullInt::S(i32::max_value() as i64)), |
| IntTy::I64 => (FullInt::S(i64::min_value() as i64), FullInt::S(i64::max_value() as i64)), |
| IntTy::Is => (FullInt::S(isize::min_value() as i64), FullInt::S(isize::max_value() as i64)), |
| }) |
| } |
| TyUint(uint_ty) => { |
| Some(match uint_ty { |
| UintTy::U8 => (FullInt::U(u8::min_value() as u64), FullInt::U(u8::max_value() as u64)), |
| UintTy::U16 => (FullInt::U(u16::min_value() as u64), FullInt::U(u16::max_value() as u64)), |
| UintTy::U32 => (FullInt::U(u32::min_value() as u64), FullInt::U(u32::max_value() as u64)), |
| UintTy::U64 => (FullInt::U(u64::min_value() as u64), FullInt::U(u64::max_value() as u64)), |
| UintTy::Us => (FullInt::U(usize::min_value() as u64), FullInt::U(usize::max_value() as u64)), |
| }) |
| } |
| _ => None, |
| } |
| } else { |
| None |
| } |
| } |
| |
| fn node_as_const_fullint(cx: &LateContext, expr: &Expr) -> Option<FullInt> { |
| use rustc::middle::const_val::ConstVal::*; |
| use rustc_const_eval::EvalHint::ExprTypeChecked; |
| use rustc_const_eval::eval_const_expr_partial; |
| use rustc_const_math::ConstInt; |
| |
| match eval_const_expr_partial(cx.tcx, expr, ExprTypeChecked, None) { |
| Ok(val) => { |
| if let Integral(const_int) = val { |
| Some(match const_int.erase_type() { |
| ConstInt::InferSigned(x) => FullInt::S(x as i64), |
| ConstInt::Infer(x) => FullInt::U(x as u64), |
| _ => unreachable!(), |
| }) |
| } else { |
| None |
| } |
| } |
| Err(_) => None, |
| } |
| } |
| |
| fn err_upcast_comparison(cx: &LateContext, span: &Span, expr: &Expr, always: bool) { |
| if let ExprCast(ref cast_val, _) = expr.node { |
| span_lint(cx, |
| INVALID_UPCAST_COMPARISONS, |
| *span, |
| &format!( |
| "because of the numeric bounds on `{}` prior to casting, this expression is always {}", |
| snippet(cx, cast_val.span, "the expression"), |
| if always { "true" } else { "false" }, |
| )); |
| } |
| } |
| |
| fn upcast_comparison_bounds_err(cx: &LateContext, span: &Span, rel: comparisons::Rel, |
| lhs_bounds: Option<(FullInt, FullInt)>, lhs: &Expr, rhs: &Expr, invert: bool) { |
| use utils::comparisons::*; |
| |
| if let Some((lb, ub)) = lhs_bounds { |
| if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) { |
| if rel == Rel::Eq || rel == Rel::Ne { |
| if norm_rhs_val < lb || norm_rhs_val > ub { |
| err_upcast_comparison(cx, span, lhs, rel == Rel::Ne); |
| } |
| } else if match rel { |
| Rel::Lt => { |
| if invert { |
| norm_rhs_val < lb |
| } else { |
| ub < norm_rhs_val |
| } |
| } |
| Rel::Le => { |
| if invert { |
| norm_rhs_val <= lb |
| } else { |
| ub <= norm_rhs_val |
| } |
| } |
| Rel::Eq | Rel::Ne => unreachable!(), |
| } { |
| err_upcast_comparison(cx, span, lhs, true) |
| } else if match rel { |
| Rel::Lt => { |
| if invert { |
| norm_rhs_val >= ub |
| } else { |
| lb >= norm_rhs_val |
| } |
| } |
| Rel::Le => { |
| if invert { |
| norm_rhs_val > ub |
| } else { |
| lb > norm_rhs_val |
| } |
| } |
| Rel::Eq | Rel::Ne => unreachable!(), |
| } { |
| err_upcast_comparison(cx, span, lhs, false) |
| } |
| } |
| } |
| } |
| |
| impl LateLintPass for InvalidUpcastComparisons { |
| fn check_expr(&mut self, cx: &LateContext, expr: &Expr) { |
| if let ExprBinary(ref cmp, ref lhs, ref rhs) = expr.node { |
| |
| let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs); |
| let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized { |
| val |
| } else { |
| return; |
| }; |
| |
| let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs); |
| let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs); |
| |
| upcast_comparison_bounds_err(cx, &expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false); |
| upcast_comparison_bounds_err(cx, &expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true); |
| } |
| } |
| } |
