+use rustc::lint::*;
use syntax::ptr::P;
-use syntax::ast;
-use syntax::ast::*;
-use syntax::ast_util::{is_comparison_binop, binop_to_string};
-use syntax::visit::{FnKind};
-use rustc::lint::{Context, LintPass, LintArray, Lint, Level};
+use rustc_front::hir::*;
+use reexport::*;
+use rustc_front::util::{is_comparison_binop, binop_to_string};
+use syntax::codemap::{Span, Spanned, ExpnFormat};
+use rustc_front::intravisit::FnKind;
use rustc::middle::ty;
-use syntax::codemap::{Span, Spanned};
-
-use utils::{match_path, snippet, span_lint, span_help_and_lint, walk_ptrs_ty};
-
-/// Handles uncategorized lints
-/// Currently handles linting of if-let-able matches
-#[allow(missing_copy_implementations)]
-pub struct MiscPass;
-
-
-declare_lint!(pub SINGLE_MATCH, Warn,
- "Warn on usage of matches with a single nontrivial arm");
-
-impl LintPass for MiscPass {
- fn get_lints(&self) -> LintArray {
- lint_array!(SINGLE_MATCH)
- }
-
- fn check_expr(&mut self, cx: &Context, expr: &Expr) {
- if let ExprMatch(ref ex, ref arms, ast::MatchSource::Normal) = expr.node {
- if arms.len() == 2 {
- if arms[0].guard.is_none() && arms[1].pats.len() == 1 {
- match arms[1].body.node {
- ExprTup(ref v) if v.is_empty() && arms[1].guard.is_none() => (),
- ExprBlock(ref b) if b.stmts.is_empty() && arms[1].guard.is_none() => (),
- _ => return
- }
- // In some cases, an exhaustive match is preferred to catch situations when
- // an enum is extended. So we only consider cases where a `_` wildcard is used
- if arms[1].pats[0].node == PatWild(PatWildSingle) &&
- arms[0].pats.len() == 1 {
- let body_code = snippet(cx, arms[0].body.span, "..");
- let suggestion = if let ExprBlock(_) = arms[0].body.node {
- body_code.into_owned()
- } else {
- format!("{{ {} }}", body_code)
- };
- span_help_and_lint(cx, SINGLE_MATCH, expr.span,
- "you seem to be trying to use match for \
- destructuring a single pattern. Did you mean to \
- use `if let`?",
- &*format!("try\nif let {} = {} {}",
- snippet(cx, arms[0].pats[0].span, ".."),
- snippet(cx, ex.span, ".."),
- suggestion)
- );
- }
- }
- }
- }
- }
-}
-
-
-declare_lint!(pub TOPLEVEL_REF_ARG, Warn, "Warn about pattern matches with top-level `ref` bindings");
+use rustc::middle::const_eval::ConstVal::Float;
+use rustc::middle::const_eval::eval_const_expr_partial;
+use rustc::middle::const_eval::EvalHint::ExprTypeChecked;
+
+use utils::{get_item_name, match_path, snippet, get_parent_expr, span_lint};
+use utils::{span_help_and_lint, walk_ptrs_ty, is_integer_literal};
+
+/// **What it does:** This lint checks for function arguments and let bindings denoted as `ref`. It is `Warn` by default.
+///
+/// **Why is this bad?** The `ref` declaration makes the function take an owned value, but turns the argument into a reference (which means that the value is destroyed when exiting the function). This adds not much value: either take a reference type, or take an owned value and create references in the body.
+///
+/// For let bindings, `let x = &foo;` is preferred over `let ref x = foo`. The type of `x` is more obvious with the former.
+///
+/// **Known problems:** If the argument is dereferenced within the function, removing the `ref` will lead to errors. This can be fixed by removing the dereferences, e.g. changing `*x` to `x` within the function.
+///
+/// **Example:** `fn foo(ref x: u8) -> bool { .. }`
+declare_lint!(pub TOPLEVEL_REF_ARG, Warn,
+ "An entire binding was declared as `ref`, in a function argument (`fn foo(ref x: Bar)`), \
+ or a `let` statement (`let ref x = foo()`). In such cases, it is preferred to take \
+ references with `&`.");
#[allow(missing_copy_implementations)]
pub struct TopLevelRefPass;
fn get_lints(&self) -> LintArray {
lint_array!(TOPLEVEL_REF_ARG)
}
+}
- fn check_fn(&mut self, cx: &Context, _: FnKind, decl: &FnDecl, _: &Block, _: Span, _: NodeId) {
- for ref arg in decl.inputs.iter() {
+impl LateLintPass for TopLevelRefPass {
+ fn check_fn(&mut self, cx: &LateContext, k: FnKind, decl: &FnDecl, _: &Block, _: Span, _: NodeId) {
+ if let FnKind::Closure = k {
+ // Does not apply to closures
+ return
+ }
+ for ref arg in &decl.inputs {
if let PatIdent(BindByRef(_), _, _) = arg.pat.node {
span_lint(cx,
TOPLEVEL_REF_ARG,
}
}
}
+ fn check_stmt(&mut self, cx: &LateContext, s: &Stmt) {
+ if_let_chain! {
+ [
+ let StmtDecl(ref d, _) = s.node,
+ let DeclLocal(ref l) = d.node,
+ let PatIdent(BindByRef(_), i, None) = l.pat.node,
+ let Some(ref init) = l.init
+ ], {
+ let tyopt = if let Some(ref ty) = l.ty {
+ format!(": {:?} ", ty)
+ } else {
+ "".to_owned()
+ };
+ span_help_and_lint(cx,
+ TOPLEVEL_REF_ARG,
+ l.pat.span,
+ "`ref` on an entire `let` pattern is discouraged, take a reference with & instead",
+ &format!("try `let {} {}= &{};`", snippet(cx, i.span, "_"),
+ tyopt, snippet(cx, init.span, "_"))
+ );
+ }
+ };
+ }
}
-declare_lint!(pub CMP_NAN, Deny, "Deny comparisons to std::f32::NAN or std::f64::NAN");
+/// **What it does:** This lint checks for comparisons to NAN. It is `Deny` by default.
+///
+/// **Why is this bad?** NAN does not compare meaningfully to anything – not even itself – so those comparisons are simply wrong.
+///
+/// **Known problems:** None
+///
+/// **Example:** `x == NAN`
+declare_lint!(pub CMP_NAN, Deny,
+ "comparisons to NAN (which will always return false, which is probably not intended)");
#[derive(Copy,Clone)]
pub struct CmpNan;
fn get_lints(&self) -> LintArray {
lint_array!(CMP_NAN)
}
+}
- fn check_expr(&mut self, cx: &Context, expr: &Expr) {
+impl LateLintPass for CmpNan {
+ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if let ExprBinary(ref cmp, ref left, ref right) = expr.node {
if is_comparison_binop(cmp.node) {
- if let &ExprPath(_, ref path) = &left.node {
+ if let ExprPath(_, ref path) = left.node {
check_nan(cx, path, expr.span);
}
- if let &ExprPath(_, ref path) = &right.node {
+ if let ExprPath(_, ref path) = right.node {
check_nan(cx, path, expr.span);
}
}
}
}
-fn check_nan(cx: &Context, path: &Path, span: Span) {
- path.segments.last().map(|seg| if seg.identifier.name == "NAN" {
+fn check_nan(cx: &LateContext, path: &Path, span: Span) {
+ path.segments.last().map(|seg| if seg.identifier.name.as_str() == "NAN" {
span_lint(cx, CMP_NAN, span,
- "doomed comparison with NAN, use `std::{f32,f64}::is_nan()` instead");
+ "doomed comparison with NAN, use `std::{f32,f64}::is_nan()` instead");
});
}
+/// **What it does:** This lint checks for (in-)equality comparisons on floating-point values (apart from zero), except in functions called `*eq*` (which probably implement equality for a type involving floats). It is `Warn` by default.
+///
+/// **Why is this bad?** Floating point calculations are usually imprecise, so asking if two values are *exactly* equal is asking for trouble. For a good guide on what to do, see [the floating point guide](http://www.floating-point-gui.de/errors/comparison).
+///
+/// **Known problems:** None
+///
+/// **Example:** `y == 1.23f64`
declare_lint!(pub FLOAT_CMP, Warn,
- "Warn on ==/!= comparison of floaty values");
+ "using `==` or `!=` on float values (as floating-point operations \
+ usually involve rounding errors, it is always better to check for approximate \
+ equality within small bounds)");
#[derive(Copy,Clone)]
pub struct FloatCmp;
fn get_lints(&self) -> LintArray {
lint_array!(FLOAT_CMP)
}
+}
- fn check_expr(&mut self, cx: &Context, expr: &Expr) {
+impl LateLintPass for FloatCmp {
+ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if let ExprBinary(ref cmp, ref left, ref right) = expr.node {
let op = cmp.node;
if (op == BiEq || op == BiNe) && (is_float(cx, left) || is_float(cx, right)) {
+ if is_allowed(cx, left) || is_allowed(cx, right) { return; }
+ if let Some(name) = get_item_name(cx, expr) {
+ let name = name.as_str();
+ if name == "eq" || name == "ne" || name == "is_nan" ||
+ name.starts_with("eq_") ||
+ name.ends_with("_eq") {
+ return;
+ }
+ }
span_lint(cx, FLOAT_CMP, expr.span, &format!(
- "{}-comparison of f32 or f64 detected. Consider changing this to `abs({} - {}) < epsilon` for some suitable value of epsilon.",
+ "{}-comparison of f32 or f64 detected. Consider changing this to \
+ `abs({} - {}) < epsilon` for some suitable value of epsilon",
binop_to_string(op), snippet(cx, left.span, ".."),
snippet(cx, right.span, "..")));
}
}
}
-fn is_float(cx: &Context, expr: &Expr) -> bool {
+fn is_allowed(cx: &LateContext, expr: &Expr) -> bool {
+ let res = eval_const_expr_partial(cx.tcx, expr, ExprTypeChecked, None);
+ if let Ok(Float(val)) = res {
+ val == 0.0 || val == ::std::f64::INFINITY || val == ::std::f64::NEG_INFINITY
+ } else { false }
+}
+
+fn is_float(cx: &LateContext, expr: &Expr) -> bool {
if let ty::TyFloat(_) = walk_ptrs_ty(cx.tcx.expr_ty(expr)).sty {
true
} else {
}
}
-declare_lint!(pub PRECEDENCE, Warn,
- "Warn on mixing bit ops with integer arithmetic without parenthesis");
-
-#[derive(Copy,Clone)]
-pub struct Precedence;
-
-impl LintPass for Precedence {
- fn get_lints(&self) -> LintArray {
- lint_array!(PRECEDENCE)
- }
-
- fn check_expr(&mut self, cx: &Context, expr: &Expr) {
- if let ExprBinary(Spanned { node: op, ..}, ref left, ref right) = expr.node {
- if is_bit_op(op) && (is_arith_expr(left) || is_arith_expr(right)) {
- span_lint(cx, PRECEDENCE, expr.span,
- "operator precedence can trip the unwary. Consider adding parenthesis to the subexpression.");
- }
- }
- }
-}
-
-fn is_arith_expr(expr : &Expr) -> bool {
- match expr.node {
- ExprBinary(Spanned { node: op, ..}, _, _) => is_arith_op(op),
- _ => false
- }
-}
-
-fn is_bit_op(op : BinOp_) -> bool {
- match op {
- BiBitXor | BiBitAnd | BiBitOr | BiShl | BiShr => true,
- _ => false
- }
-}
-
-fn is_arith_op(op : BinOp_) -> bool {
- match op {
- BiAdd | BiSub | BiMul | BiDiv | BiRem => true,
- _ => false
- }
-}
-
+/// **What it does:** This lint checks for conversions to owned values just for the sake of a comparison. It is `Warn` by default.
+///
+/// **Why is this bad?** The comparison can operate on a reference, so creating an owned value effectively throws it away directly afterwards, which is needlessly consuming code and heap space.
+///
+/// **Known problems:** None
+///
+/// **Example:** `x.to_owned() == y`
declare_lint!(pub CMP_OWNED, Warn,
- "Warn on creating an owned string just for comparison");
+ "creating owned instances for comparing with others, e.g. `x == \"foo\".to_string()`");
#[derive(Copy,Clone)]
pub struct CmpOwned;
fn get_lints(&self) -> LintArray {
lint_array!(CMP_OWNED)
}
+}
- fn check_expr(&mut self, cx: &Context, expr: &Expr) {
+impl LateLintPass for CmpOwned {
+ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if let ExprBinary(ref cmp, ref left, ref right) = expr.node {
if is_comparison_binop(cmp.node) {
- check_to_owned(cx, left, right.span);
- check_to_owned(cx, right, left.span)
+ check_to_owned(cx, left, right.span, true, cmp.span);
+ check_to_owned(cx, right, left.span, false, cmp.span)
}
}
}
}
-fn check_to_owned(cx: &Context, expr: &Expr, other_span: Span) {
- match &expr.node {
- &ExprMethodCall(Spanned{node: ref ident, ..}, _, ref args) => {
- let name = ident.name;
- if name == "to_string" ||
- name == "to_owned" && is_str_arg(cx, args) {
- span_lint(cx, CMP_OWNED, expr.span, &format!(
- "this creates an owned instance just for comparison. \
- Consider using `{}.as_slice()` to compare without allocation.",
- snippet(cx, other_span, "..")))
+fn check_to_owned(cx: &LateContext, expr: &Expr, other_span: Span, left: bool, op: Span) {
+ let snip = match expr.node {
+ ExprMethodCall(Spanned{node: ref name, ..}, _, ref args) if args.len() == 1 => {
+ if name.as_str() == "to_string" ||
+ name.as_str() == "to_owned" && is_str_arg(cx, args) {
+ snippet(cx, args[0].span, "..")
+ } else {
+ return
}
- },
- &ExprCall(ref path, _) => {
- if let &ExprPath(None, ref path) = &path.node {
+ }
+ ExprCall(ref path, ref v) if v.len() == 1 => {
+ if let ExprPath(None, ref path) = path.node {
if match_path(path, &["String", "from_str"]) ||
match_path(path, &["String", "from"]) {
- span_lint(cx, CMP_OWNED, expr.span, &format!(
- "this creates an owned instance just for comparison. \
- Consider using `{}.as_slice()` to compare without allocation.",
- snippet(cx, other_span, "..")))
+ snippet(cx, v[0].span, "..")
+ } else {
+ return
}
+ } else {
+ return
}
- },
- _ => ()
+ }
+ _ => return
+ };
+ if left {
+ span_lint(cx, CMP_OWNED, expr.span, &format!(
+ "this creates an owned instance just for comparison. Consider using \
+ `{} {} {}` to compare without allocation", snip,
+ snippet(cx, op, "=="), snippet(cx, other_span, "..")));
+ } else {
+ span_lint(cx, CMP_OWNED, expr.span, &format!(
+ "this creates an owned instance just for comparison. Consider using \
+ `{} {} {}` to compare without allocation",
+ snippet(cx, other_span, ".."), snippet(cx, op, "=="), snip));
}
+
}
-fn is_str_arg(cx: &Context, args: &[P<Expr>]) -> bool {
+fn is_str_arg(cx: &LateContext, args: &[P<Expr>]) -> bool {
args.len() == 1 && if let ty::TyStr =
- walk_ptrs_ty(cx.tcx.expr_ty(&*args[0])).sty { true } else { false }
+ walk_ptrs_ty(cx.tcx.expr_ty(&args[0])).sty { true } else { false }
}
-declare_lint!(pub MODULO_ONE, Warn, "Warn on expressions that include % 1, which is always 0");
+/// **What it does:** This lint checks for getting the remainder of a division by one. It is `Warn` by default.
+///
+/// **Why is this bad?** The result can only ever be zero. No one will write such code deliberately, unless trying to win an Underhanded Rust Contest. Even for that contest, it's probably a bad idea. Use something more underhanded.
+///
+/// **Known problems:** None
+///
+/// **Example:** `x % 1`
+declare_lint!(pub MODULO_ONE, Warn, "taking a number modulo 1, which always returns 0");
#[derive(Copy,Clone)]
pub struct ModuloOne;
fn get_lints(&self) -> LintArray {
lint_array!(MODULO_ONE)
}
+}
- fn check_expr(&mut self, cx: &Context, expr: &Expr) {
+impl LateLintPass for ModuloOne {
+ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if let ExprBinary(ref cmp, _, ref right) = expr.node {
- if let &Spanned {node: BinOp_::BiRem, ..} = cmp {
- if is_lit_one(right) {
+ if let Spanned {node: BinOp_::BiRem, ..} = *cmp {
+ if is_integer_literal(right, 1) {
cx.span_lint(MODULO_ONE, expr.span, "any number modulo 1 will be 0");
}
}
}
}
-fn is_lit_one(expr: &Expr) -> bool {
- if let ExprLit(ref spanned) = expr.node {
- if let LitInt(1, _) = spanned.node {
- return true;
+/// **What it does:** This lint checks for patterns in the form `name @ _`.
+///
+/// **Why is this bad?** It's almost always more readable to just use direct bindings.
+///
+/// **Known problems:** None
+///
+/// **Example**:
+/// ```
+/// match v {
+/// Some(x) => (),
+/// y @ _ => (), // easier written as `y`,
+/// }
+/// ```
+declare_lint!(pub REDUNDANT_PATTERN, Warn, "using `name @ _` in a pattern");
+
+#[derive(Copy,Clone)]
+pub struct PatternPass;
+
+impl LintPass for PatternPass {
+ fn get_lints(&self) -> LintArray {
+ lint_array!(REDUNDANT_PATTERN)
+ }
+}
+
+impl LateLintPass for PatternPass {
+ fn check_pat(&mut self, cx: &LateContext, pat: &Pat) {
+ if let PatIdent(_, ref ident, Some(ref right)) = pat.node {
+ if right.node == PatWild {
+ cx.span_lint(REDUNDANT_PATTERN, pat.span, &format!(
+ "the `{} @ _` pattern can be written as just `{}`",
+ ident.node.name, ident.node.name));
+ }
+ }
+ }
+}
+
+
+/// **What it does:** This lint checks for the use of bindings with a single leading underscore
+///
+/// **Why is this bad?** A single leading underscore is usually used to indicate that a binding
+/// will not be used. Using such a binding breaks this expectation.
+///
+/// **Known problems:** None
+///
+/// **Example**:
+/// ```
+/// let _x = 0;
+/// let y = _x + 1; // Here we are using `_x`, even though it has a leading underscore.
+/// // We should rename `_x` to `x`
+/// ```
+declare_lint!(pub USED_UNDERSCORE_BINDING, Warn,
+ "using a binding which is prefixed with an underscore");
+
+#[derive(Copy, Clone)]
+pub struct UsedUnderscoreBinding;
+
+impl LintPass for UsedUnderscoreBinding {
+ fn get_lints(&self) -> LintArray {
+ lint_array!(USED_UNDERSCORE_BINDING)
+ }
+}
+
+impl LateLintPass for UsedUnderscoreBinding {
+ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
+ if in_attributes_expansion(cx, expr) { // Don't lint things expanded by #[derive(...)], etc
+ return;
+ }
+ let needs_lint = match expr.node {
+ ExprPath(_, ref path) => {
+ let ident = path.segments.last()
+ .expect("path should always have at least one segment")
+ .identifier;
+ ident.name.as_str().chars().next() == Some('_') //starts with '_'
+ && ident.name.as_str().chars().skip(1).next() != Some('_') //doesn't start with "__"
+ && ident.name != ident.unhygienic_name //not in bang macro
+ && is_used(cx, expr)
+ },
+ ExprField(_, spanned) => {
+ let name = spanned.node.as_str();
+ name.chars().next() == Some('_')
+ && name.chars().skip(1).next() != Some('_')
+ },
+ _ => false
+ };
+ if needs_lint {
+ cx.span_lint(USED_UNDERSCORE_BINDING, expr.span,
+ "used binding which is prefixed with an underscore. A leading underscore \
+ signals that a binding will not be used.");
+ }
+ }
+}
+
+/// Heuristic to see if an expression is used. Should be compatible with `unused_variables`'s idea
+/// of what it means for an expression to be "used".
+fn is_used(cx: &LateContext, expr: &Expr) -> bool {
+ if let Some(ref parent) = get_parent_expr(cx, expr) {
+ match parent.node {
+ ExprAssign(_, ref rhs) => **rhs == *expr,
+ ExprAssignOp(_, _, ref rhs) => **rhs == *expr,
+ _ => is_used(cx, &parent)
}
}
- false
+ else {
+ true
+ }
+}
+
+/// Test whether an expression is in a macro expansion (e.g. something generated by #[derive(...)]
+/// or the like)
+fn in_attributes_expansion(cx: &LateContext, expr: &Expr) -> bool {
+ cx.sess().codemap().with_expn_info(expr.span.expn_id, |info_opt| {
+ info_opt.map_or(false, |info| {
+ match info.callee.format {
+ ExpnFormat::MacroAttribute(_) => true,
+ _ => false,
+ }
+ })
+ })
}
projects / rust.git / blobdiff