83a82a1d86
The default level is always given in the declare_lint! macro, no need to add it inconsistently in the documentation.
66 lines
1.9 KiB
Rust
66 lines
1.9 KiB
Rust
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::middle::def::Def;
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use rustc_front::hir::{Expr, ExprCall, ExprLit, ExprPath, ExprStruct};
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use rustc_front::hir::{Stmt, StmtSemi};
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use utils::in_macro;
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use utils::span_lint;
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/// **What it does:** This lint checks for statements which have no effect.
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///
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/// **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.
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///
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/// **Known problems:** None.
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///
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/// **Example:** `0;`
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declare_lint! {
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pub NO_EFFECT,
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Warn,
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"statements with no effect"
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}
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fn has_no_effect(cx: &LateContext, expr: &Expr) -> bool {
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if in_macro(cx, expr.span) {
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return false;
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}
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match expr.node {
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ExprLit(..) |
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ExprPath(..) => true,
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ExprStruct(_, ref fields, ref base) => {
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fields.iter().all(|field| has_no_effect(cx, &field.expr)) &&
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match *base {
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Some(ref base) => has_no_effect(cx, base),
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None => true,
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}
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}
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ExprCall(ref callee, ref args) => {
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let def = cx.tcx.def_map.borrow().get(&callee.id).map(|d| d.full_def());
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match def {
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Some(Def::Struct(..)) |
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Some(Def::Variant(..)) => args.iter().all(|arg| has_no_effect(cx, arg)),
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_ => false,
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}
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}
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_ => false,
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}
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}
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#[derive(Copy, Clone)]
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pub struct NoEffectPass;
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impl LintPass for NoEffectPass {
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fn get_lints(&self) -> LintArray {
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lint_array!(NO_EFFECT)
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}
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}
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impl LateLintPass for NoEffectPass {
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fn check_stmt(&mut self, cx: &LateContext, stmt: &Stmt) {
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if let StmtSemi(ref expr, _) = stmt.node {
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if has_no_effect(cx, expr) {
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span_lint(cx, NO_EFFECT, stmt.span, "statement with no effect");
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}
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}
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}
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}
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