use rustc_front::hir::*;
use reexport::*;
use rustc_front::util::{is_comparison_binop, binop_to_string};
-use syntax::codemap::{Span, Spanned};
-use rustc_front::visit::FnKind;
+use syntax::codemap::{Span, Spanned, ExpnFormat};
+use rustc_front::intravisit::FnKind;
use rustc::middle::ty;
+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, span_lint, walk_ptrs_ty};
-use consts::constant;
+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,
- "a function argument is declared `ref` (i.e. `fn foo(ref x: u8)`, but not \
- `fn foo((ref x, ref y): (u8, u8))`)");
+ "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, k: FnKind, decl: &FnDecl, _: &Block, _: Span, _: NodeId) {
+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
}
}
}
+ 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, "_"))
+ );
+ }
+ };
+ }
}
+/// **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)");
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");
});
}
+/// **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,
"using `==` or `!=` on float values (as floating-point operations \
usually involve rounding errors, it is always better to check for approximate \
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 constant(cx, left).or_else(|| constant(cx, right)).map_or(
- false, |c| c.0.as_float().map_or(false, |f| f == 0.0)) {
- return;
- }
+ if is_allowed(cx, left) || is_allowed(cx, right) { return; }
if let Some(name) = get_item_name(cx, expr) {
- if name == "eq" || name == "ne" ||
- name.as_str().starts_with("eq_") ||
- name.as_str().ends_with("_eq") {
+ let name = name.as_str();
+ if name == "eq" || name == "ne" || name == "is_nan" ||
+ name.starts_with("eq_") ||
+ name.ends_with("_eq") {
return;
}
}
}
}
-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 {
}
}
+/// **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,
"creating owned instances for comparing with others, e.g. `x == \"foo\".to_string()`");
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 }
}
+/// **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)]
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;
- }
- }
- false
-}
-
+/// **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)]
fn get_lints(&self) -> LintArray {
lint_array!(REDUNDANT_PATTERN)
}
+}
- fn check_pat(&mut self, cx: &Context, pat: &Pat) {
+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(PatWildSingle) {
+ 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)
+ }
+ }
+ 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