rust/src/no_effect.rs
2015-10-29 15:50:35 +09:00

62 lines
1.7 KiB
Rust

use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use rustc::middle::def::{DefStruct, DefVariant};
use rustc_front::hir::{Expr, ExprCall, ExprLit, ExprPath, ExprStruct};
use rustc_front::hir::{Stmt, StmtSemi};
use utils::in_macro;
use utils::span_lint;
declare_lint! {
pub NO_EFFECT,
Warn,
"statements with no effect"
}
fn has_no_effect(cx: &LateContext, expr: &Expr) -> bool {
if in_macro(cx, expr.span) {
return false;
}
match expr.node {
ExprLit(..) |
ExprPath(..) => true,
ExprStruct(_, ref fields, ref base) => {
fields.iter().all(|field| has_no_effect(cx, &field.expr)) &&
match *base {
Some(ref base) => has_no_effect(cx, base),
None => true,
}
}
ExprCall(ref callee, ref args) => {
let def = cx.tcx.def_map.borrow().get(&callee.id).map(|d| d.full_def());
match def {
Some(DefStruct(..)) |
Some(DefVariant(..)) => {
args.iter().all(|arg| has_no_effect(cx, arg))
}
_ => false,
}
}
_ => false,
}
}
#[derive(Copy, Clone)]
pub struct NoEffectPass;
impl LintPass for NoEffectPass {
fn get_lints(&self) -> LintArray {
lint_array!(NO_EFFECT)
}
}
impl LateLintPass for NoEffectPass {
fn check_stmt(&mut self, cx: &LateContext, stmt: &Stmt) {
if let StmtSemi(ref expr, _) = stmt.node {
if has_no_effect(cx, expr) {
span_lint(cx, NO_EFFECT, stmt.span,
"statement with no effect");
}
}
}
}