rust/clippy_lints/src/assertions_on_constants.rs
2019-03-05 18:45:08 -05:00

85 lines
3.2 KiB
Rust

use crate::consts::{constant, Constant};
use crate::rustc::hir::{Expr, ExprKind};
use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use crate::rustc::{declare_tool_lint, lint_array};
use crate::syntax::ast::LitKind;
use crate::utils::{in_macro, is_direct_expn_of, span_help_and_lint};
use if_chain::if_chain;
declare_clippy_lint! {
/// **What it does:** Check to call assert!(true/false)
///
/// **Why is this bad?** Will be optimized out by the compiler or should probably be replaced by a
/// panic!() or unreachable!()
///
/// **Known problems:** None
///
/// **Example:**
/// ```no_run
/// assert!(false);
/// // or
/// assert!(true);
/// // or
/// const B: bool = false;
/// assert!(B);
/// ```
pub ASSERTIONS_ON_CONSTANTS,
style,
"assert!(true/false) will be optimized out by the compiler/should probably be replaced by a panic!() or unreachable!()"
}
pub struct AssertionsOnConstants;
impl LintPass for AssertionsOnConstants {
fn get_lints(&self) -> LintArray {
lint_array![ASSERTIONS_ON_CONSTANTS]
}
fn name(&self) -> &'static str {
"AssertionsOnConstants"
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssertionsOnConstants {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
if_chain! {
if let Some(assert_span) = is_direct_expn_of(e.span, "assert");
if !in_macro(assert_span)
|| is_direct_expn_of(assert_span, "debug_assert").map_or(false, |span| !in_macro(span));
if let ExprKind::Unary(_, ref lit) = e.node;
then {
if let ExprKind::Lit(ref inner) = lit.node {
match inner.node {
LitKind::Bool(true) => {
span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
"assert!(true) will be optimized out by the compiler",
"remove it");
},
LitKind::Bool(false) => {
span_help_and_lint(
cx, ASSERTIONS_ON_CONSTANTS, e.span,
"assert!(false) should probably be replaced",
"use panic!() or unreachable!()");
},
_ => (),
}
} else if let Some(bool_const) = constant(cx, cx.tables, lit) {
match bool_const.0 {
Constant::Bool(true) => {
span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
"assert!(const: true) will be optimized out by the compiler",
"remove it");
},
Constant::Bool(false) => {
span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
"assert!(const: false) should probably be replaced",
"use panic!() or unreachable!()");
},
_ => (),
}
}
}
}
}
}