-// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-
-use crate::rustc::hir::def::Def;
-use crate::rustc::hir::{BinOpKind, BlockCheckMode, Expr, ExprKind, Stmt, StmtKind, UnsafeSource};
-use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use crate::rustc::{declare_tool_lint, lint_array};
-use crate::rustc_errors::Applicability;
use crate::utils::{has_drop, in_macro, snippet_opt, span_lint, span_lint_and_sugg};
+use rustc::hir::def::Def;
+use rustc::hir::{BinOpKind, BlockCheckMode, Expr, ExprKind, Stmt, StmtKind, UnsafeSource};
+use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use rustc::{declare_tool_lint, lint_array};
+use rustc_errors::Applicability;
use std::ops::Deref;
-/// **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.
-///
-/// **Known problems:** None.
-///
-/// **Example:**
-/// ```rust
-/// 0;
-/// ```
declare_clippy_lint! {
+ /// **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.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// 0;
+ /// ```
pub NO_EFFECT,
complexity,
"statements with no effect"
}
-/// **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 readability.
-///
-/// **Known problems:** None.
-///
-/// **Example:**
-/// ```rust
-/// compute_array()[0];
-/// ```
declare_clippy_lint! {
+ /// **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 readability.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// compute_array()[0];
+ /// ```
pub UNNECESSARY_OPERATION,
complexity,
"outer expressions with no effect"
}
match expr.node {
ExprKind::Lit(..) | ExprKind::Closure(.., _) => true,
- ExprKind::Path(..) => !has_drop(cx, expr),
+ ExprKind::Path(..) => !has_drop(cx, cx.tables.expr_ty(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::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,
- }
- },
- 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(..) => {
- !has_drop(cx, expr) && args.iter().all(|arg| has_no_effect(cx, arg))
- },
- _ => false,
- }
- } else {
- false
+ !has_drop(cx, cx.tables.expr_ty(expr))
+ && fields.iter().all(|field| has_no_effect(cx, &field.expr))
+ && match *base {
+ Some(ref base) => has_no_effect(cx, base),
+ None => true,
+ }
},
- ExprKind::Block(ref block, _) => {
- block.stmts.is_empty() && if let Some(ref expr) = block.expr {
- has_no_effect(cx, expr)
+ 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::Ctor(..) => {
+ !has_drop(cx, cx.tables.expr_ty(expr)) && args.iter().all(|arg| has_no_effect(cx, arg))
+ },
+ _ => false,
+ }
} 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,
}
}
fn get_lints(&self) -> LintArray {
lint_array!(NO_EFFECT, UNNECESSARY_OPERATION)
}
+
+ fn name(&self) -> &'static str {
+ "NoEffect"
+ }
}
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 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) {
}
}
-
fn reduce_expression<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<Vec<&'a Expr>> {
if in_macro(expr.span) {
return None;
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::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, cx.tables.expr_ty(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,
+ 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::Ctor(..) if !has_drop(cx, cx.tables.expr_ty(expr)) => {
+ Some(args.iter().collect())
+ },
+ _ => None,
+ }
+ } else {
+ None
}
- } else {
- None
},
ExprKind::Block(ref block, _) => {
if block.stmts.is_empty() {
projects / rust.git / blobdiff