use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::hir::def::{Def, PathResolution};
-use rustc::hir::{Expr, Expr_, Stmt, StmtSemi, BlockCheckMode, UnsafeSource};
-use utils::{in_macro, span_lint, snippet_opt, span_lint_and_then};
+use rustc::{declare_lint, lint_array};
+use rustc::hir::def::Def;
+use rustc::hir::{BinOpKind, BlockCheckMode, Expr, ExprKind, Stmt, StmtKind, UnsafeSource};
+use crate::utils::{has_drop, in_macro, snippet_opt, span_lint, span_lint_and_sugg};
use std::ops::Deref;
-/// **What it does:** This lint checks for statements which have no effect.
+/// **What it does:** Checks for statements which have no effect.
///
-/// **Why is this bad?** Similar to dead code, these statements are actually executed. However, as they have no effect, all they do is make the code less readable.
+/// **Why is this bad?** Similar to dead code, these statements are actually
+/// executed. However, as they have no effect, all they do is make the code less
+/// readable.
///
/// **Known problems:** None.
///
-/// **Example:** `0;`
-declare_lint! {
+/// **Example:**
+/// ```rust
+/// 0;
+/// ```
+declare_clippy_lint! {
pub NO_EFFECT,
- Warn,
+ complexity,
"statements with no effect"
}
-/// **What it does:** This lint checks for expression statements that can be reduced to a sub-expression
+/// **What it does:** Checks for expression statements that can be reduced to a
+/// sub-expression.
///
-/// **Why is this bad?** Expressions by themselves often have no side-effects. Having such expressions reduces redability.
+/// **Why is this bad?** Expressions by themselves often have no side-effects.
+/// Having such expressions reduces readability.
///
/// **Known problems:** None.
///
-/// **Example:** `compute_array()[0];`
-declare_lint! {
+/// **Example:**
+/// ```rust
+/// compute_array()[0];
+/// ```
+declare_clippy_lint! {
pub UNNECESSARY_OPERATION,
- Warn,
+ complexity,
"outer expressions with no effect"
}
fn has_no_effect(cx: &LateContext, expr: &Expr) -> bool {
- if in_macro(cx, expr.span) {
+ if in_macro(expr.span) {
return false;
}
match expr.node {
- Expr_::ExprLit(..) |
- Expr_::ExprClosure(..) |
- Expr_::ExprPath(..) => true,
- Expr_::ExprIndex(ref a, ref b) |
- Expr_::ExprBinary(_, ref a, ref b) => has_no_effect(cx, a) && has_no_effect(cx, b),
- Expr_::ExprVec(ref v) |
- Expr_::ExprTup(ref v) => v.iter().all(|val| has_no_effect(cx, val)),
- Expr_::ExprRepeat(ref inner, _) |
- Expr_::ExprCast(ref inner, _) |
- Expr_::ExprType(ref inner, _) |
- Expr_::ExprUnary(_, ref inner) |
- Expr_::ExprField(ref inner, _) |
- Expr_::ExprTupField(ref inner, _) |
- Expr_::ExprAddrOf(_, ref inner) |
- Expr_::ExprBox(ref inner) => has_no_effect(cx, inner),
- Expr_::ExprStruct(_, ref fields, ref base) => {
- fields.iter().all(|field| has_no_effect(cx, &field.expr)) &&
- match *base {
+ ExprKind::Lit(..) | ExprKind::Closure(.., _) => true,
+ ExprKind::Path(..) => !has_drop(cx, expr),
+ ExprKind::Index(ref a, ref b) | ExprKind::Binary(_, ref a, ref b) => {
+ has_no_effect(cx, a) && has_no_effect(cx, b)
+ },
+ ExprKind::Array(ref v) | ExprKind::Tup(ref v) => v.iter().all(|val| has_no_effect(cx, val)),
+ ExprKind::Repeat(ref inner, _) |
+ ExprKind::Cast(ref inner, _) |
+ ExprKind::Type(ref inner, _) |
+ ExprKind::Unary(_, ref inner) |
+ ExprKind::Field(ref inner, _) |
+ ExprKind::AddrOf(_, ref inner) |
+ ExprKind::Box(ref inner) => has_no_effect(cx, inner),
+ ExprKind::Struct(_, ref fields, ref base) => {
+ !has_drop(cx, expr) && fields.iter().all(|field| has_no_effect(cx, &field.expr)) && match *base {
Some(ref base) => has_no_effect(cx, base),
None => true,
}
- }
- Expr_::ExprCall(ref callee, ref args) => {
- let def = cx.tcx.def_map.borrow().get(&callee.id).map(|d| d.full_def());
+ },
+ ExprKind::Call(ref callee, ref args) => if let ExprKind::Path(ref qpath) = callee.node {
+ let def = cx.tables.qpath_def(qpath, callee.hir_id);
match def {
- Some(Def::Struct(..)) |
- Some(Def::Variant(..)) => args.iter().all(|arg| has_no_effect(cx, arg)),
+ Def::Struct(..) | Def::Variant(..) | Def::StructCtor(..) | Def::VariantCtor(..) => {
+ !has_drop(cx, expr) && args.iter().all(|arg| has_no_effect(cx, arg))
+ },
_ => false,
}
- }
- Expr_::ExprBlock(ref block) => {
- block.stmts.is_empty() &&
- if let Some(ref expr) = block.expr {
+ } else {
+ false
+ },
+ ExprKind::Block(ref block, _) => {
+ block.stmts.is_empty() && if let Some(ref expr) = block.expr {
has_no_effect(cx, expr)
} else {
false
}
- }
+ },
_ => false,
}
}
#[derive(Copy, Clone)]
-pub struct NoEffectPass;
+pub struct Pass;
-impl LintPass for NoEffectPass {
+impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(NO_EFFECT, UNNECESSARY_OPERATION)
}
}
-impl LateLintPass for NoEffectPass {
- fn check_stmt(&mut self, cx: &LateContext, stmt: &Stmt) {
- if let StmtSemi(ref expr, _) = stmt.node {
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
+ fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
+ if let StmtKind::Semi(ref expr, _) = stmt.node {
if has_no_effect(cx, expr) {
span_lint(cx, NO_EFFECT, stmt.span, "statement with no effect");
} else if let Some(reduced) = reduce_expression(cx, expr) {
let mut snippet = String::new();
for e in reduced {
- if in_macro(cx, e.span) {
+ if in_macro(e.span) {
return;
}
if let Some(snip) = snippet_opt(cx, e.span) {
return;
}
}
- span_lint_and_then(cx, UNNECESSARY_OPERATION, stmt.span, "statement can be reduced", |db| {
- db.span_suggestion(stmt.span, "replace it with", snippet);
- });
+ span_lint_and_sugg(
+ cx,
+ UNNECESSARY_OPERATION,
+ stmt.span,
+ "statement can be reduced",
+ "replace it with",
+ snippet,
+ );
}
}
}
fn reduce_expression<'a>(cx: &LateContext, expr: &'a Expr) -> Option<Vec<&'a Expr>> {
- if in_macro(cx, expr.span) {
+ if in_macro(expr.span) {
return None;
}
match expr.node {
- Expr_::ExprIndex(ref a, ref b) |
- Expr_::ExprBinary(_, ref a, ref b) => Some(vec![&**a, &**b]),
- Expr_::ExprVec(ref v) |
- Expr_::ExprTup(ref v) => Some(v.iter().map(Deref::deref).collect()),
- Expr_::ExprRepeat(ref inner, _) |
- Expr_::ExprCast(ref inner, _) |
- Expr_::ExprType(ref inner, _) |
- Expr_::ExprUnary(_, ref inner) |
- Expr_::ExprField(ref inner, _) |
- Expr_::ExprTupField(ref inner, _) |
- Expr_::ExprAddrOf(_, ref inner) |
- Expr_::ExprBox(ref inner) => reduce_expression(cx, inner).or_else(|| Some(vec![inner])),
- Expr_::ExprStruct(_, ref fields, ref base) => Some(fields.iter().map(|f| &f.expr).chain(base).map(Deref::deref).collect()),
- Expr_::ExprCall(ref callee, ref args) => {
- match cx.tcx.def_map.borrow().get(&callee.id).map(PathResolution::full_def) {
- Some(Def::Struct(..)) |
- Some(Def::Variant(..)) => Some(args.iter().map(Deref::deref).collect()),
+ ExprKind::Index(ref a, ref b) => Some(vec![&**a, &**b]),
+ ExprKind::Binary(ref binop, ref a, ref b) if binop.node != BinOpKind::And && binop.node != BinOpKind::Or => {
+ Some(vec![&**a, &**b])
+ },
+ ExprKind::Array(ref v) | ExprKind::Tup(ref v) => Some(v.iter().collect()),
+ ExprKind::Repeat(ref inner, _) |
+ ExprKind::Cast(ref inner, _) |
+ ExprKind::Type(ref inner, _) |
+ ExprKind::Unary(_, ref inner) |
+ ExprKind::Field(ref inner, _) |
+ ExprKind::AddrOf(_, ref inner) |
+ ExprKind::Box(ref inner) => reduce_expression(cx, inner).or_else(|| Some(vec![inner])),
+ ExprKind::Struct(_, ref fields, ref base) => if has_drop(cx, expr) {
+ None
+ } else {
+ Some(
+ fields
+ .iter()
+ .map(|f| &f.expr)
+ .chain(base)
+ .map(Deref::deref)
+ .collect(),
+ )
+ },
+ ExprKind::Call(ref callee, ref args) => if let ExprKind::Path(ref qpath) = callee.node {
+ let def = cx.tables.qpath_def(qpath, callee.hir_id);
+ match def {
+ Def::Struct(..) | Def::Variant(..) | Def::StructCtor(..) | Def::VariantCtor(..)
+ if !has_drop(cx, expr) =>
+ {
+ Some(args.iter().collect())
+ },
_ => None,
}
- }
- Expr_::ExprBlock(ref block) => {
+ } else {
+ None
+ },
+ ExprKind::Block(ref block, _) => {
if block.stmts.is_empty() {
- block.expr.as_ref().and_then(|e| match block.rules {
- BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) => None,
- BlockCheckMode::DefaultBlock => Some(vec![&**e]),
- // in case of compiler-inserted signaling blocks
- _ => reduce_expression(cx, e),
+ block.expr.as_ref().and_then(|e| {
+ match block.rules {
+ BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) => None,
+ BlockCheckMode::DefaultBlock => Some(vec![&**e]),
+ // in case of compiler-inserted signaling blocks
+ _ => reduce_expression(cx, e),
+ }
})
} else {
None
}
- }
+ },
_ => None,
}
}
projects / rust.git / blobdiff