2015-05-01 22:35:49 +00:00
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//! Checks for needless boolean results of if-else expressions
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//!
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2015-05-04 05:17:15 +00:00
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//! This lint is **warn** by default
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2015-05-01 22:35:49 +00:00
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2018-05-30 08:15:50 +00:00
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use crate::utils::sugg::Sugg;
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2018-11-30 13:21:11 +00:00
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use crate::utils::{in_macro, span_lint, span_lint_and_sugg};
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2018-12-29 15:04:45 +00:00
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::{declare_tool_lint, lint_array};
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use rustc_errors::Applicability;
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use syntax::ast::LitKind;
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use syntax::source_map::Spanned;
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2015-05-01 22:35:49 +00:00
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2017-08-09 07:30:56 +00:00
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/// **What it does:** Checks for expressions of the form `if c { true } else {
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/// false }`
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2016-07-15 22:25:44 +00:00
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/// (or vice versa) and suggest using the condition directly.
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2015-12-11 00:22:27 +00:00
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///
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/// **Why is this bad?** Redundant code.
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///
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2016-08-06 07:55:04 +00:00
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/// **Known problems:** Maybe false positives: Sometimes, the two branches are
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/// painstakingly documented (which we of course do not detect), so they *may*
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/// have some value. Even then, the documentation can be rewritten to match the
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/// shorter code.
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2015-12-11 00:22:27 +00:00
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///
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2016-07-15 22:25:44 +00:00
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/// **Example:**
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/// ```rust
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2018-11-27 20:14:15 +00:00
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/// if x {
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/// false
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/// } else {
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/// true
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/// }
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2016-07-15 22:25:44 +00:00
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/// ```
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2018-03-28 13:24:26 +00:00
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declare_clippy_lint! {
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2018-11-27 20:49:09 +00:00
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pub NEEDLESS_BOOL,
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complexity,
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"if-statements with plain booleans in the then- and else-clause, e.g. `if p { true } else { false }`"
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2015-05-01 22:35:49 +00:00
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}
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2018-12-07 00:50:16 +00:00
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/// **What it does:** Checks for expressions of the form `x == true`,
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/// `x != true` and order comparisons such as `x < true` (or vice versa) and
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/// suggest using the variable directly.
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2016-02-09 19:10:22 +00:00
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///
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/// **Why is this bad?** Unnecessary code.
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///
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/// **Known problems:** None.
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///
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2016-08-06 07:55:04 +00:00
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/// **Example:**
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/// ```rust
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2018-11-27 20:14:15 +00:00
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/// if x == true {} // could be `if x { }`
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2016-08-06 07:55:04 +00:00
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/// ```
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2018-03-28 13:24:26 +00:00
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declare_clippy_lint! {
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2016-02-09 19:10:22 +00:00
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pub BOOL_COMPARISON,
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2018-03-29 11:41:53 +00:00
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complexity,
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2018-11-30 13:21:11 +00:00
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"comparing a variable to a boolean, e.g. `if x == true` or `if x != true`"
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2016-02-09 19:10:22 +00:00
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}
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2017-08-09 07:30:56 +00:00
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#[derive(Copy, Clone)]
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2015-05-01 22:35:49 +00:00
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pub struct NeedlessBool;
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impl LintPass for NeedlessBool {
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fn get_lints(&self) -> LintArray {
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lint_array!(NEEDLESS_BOOL)
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}
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2015-09-19 02:53:04 +00:00
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}
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2015-08-11 18:22:20 +00:00
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2016-12-07 12:13:40 +00:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessBool {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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2016-03-14 15:41:41 +00:00
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use self::Expression::*;
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2018-07-12 07:30:57 +00:00
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if let ExprKind::If(ref pred, ref then_block, Some(ref else_expr)) = e.node {
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2019-01-20 15:15:00 +00:00
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2016-07-03 23:17:31 +00:00
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let reduce = |ret, not| {
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2018-11-27 14:13:57 +00:00
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let mut applicability = Applicability::MachineApplicable;
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let snip = Sugg::hir_with_applicability(cx, pred, "<predicate>", &mut applicability);
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2016-12-20 17:21:30 +00:00
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let snip = if not { !snip } else { snip };
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2016-07-03 23:17:31 +00:00
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2019-01-20 15:15:00 +00:00
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let mut hint = if ret {
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2016-07-06 13:36:42 +00:00
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format!("return {}", snip)
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2016-07-03 23:17:31 +00:00
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} else {
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snip.to_string()
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};
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2019-01-20 15:15:00 +00:00
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if parent_node_is_if_expr(&e, &cx) {
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hint = format!("{{ {} }}", hint);
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}
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2017-08-09 07:30:56 +00:00
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span_lint_and_sugg(
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cx,
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NEEDLESS_BOOL,
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e.span,
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"this if-then-else expression returns a bool literal",
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"you can reduce it to",
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hint,
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2018-11-27 14:13:57 +00:00
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applicability,
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2017-08-09 07:30:56 +00:00
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);
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2016-03-14 15:41:41 +00:00
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};
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2018-07-12 07:30:57 +00:00
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if let ExprKind::Block(ref then_block, _) = then_block.node {
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2017-04-12 09:06:32 +00:00
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match (fetch_bool_block(then_block), fetch_bool_expr(else_expr)) {
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2017-09-05 09:33:04 +00:00
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(RetBool(true), RetBool(true)) | (Bool(true), Bool(true)) => {
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2017-08-09 07:30:56 +00:00
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span_lint(
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cx,
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NEEDLESS_BOOL,
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e.span,
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"this if-then-else expression will always return true",
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);
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2017-04-12 09:06:32 +00:00
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},
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2017-09-05 09:33:04 +00:00
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(RetBool(false), RetBool(false)) | (Bool(false), Bool(false)) => {
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2017-08-09 07:30:56 +00:00
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span_lint(
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cx,
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NEEDLESS_BOOL,
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e.span,
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"this if-then-else expression will always return false",
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);
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2017-04-12 09:06:32 +00:00
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},
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(RetBool(true), RetBool(false)) => reduce(true, false),
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(Bool(true), Bool(false)) => reduce(false, false),
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(RetBool(false), RetBool(true)) => reduce(true, true),
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(Bool(false), Bool(true)) => reduce(false, true),
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_ => (),
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}
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2017-03-31 21:46:08 +00:00
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} else {
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2018-07-12 07:30:57 +00:00
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panic!("IfExpr 'then' node is not an ExprKind::Block");
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2017-03-31 21:46:08 +00:00
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}
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2015-08-11 18:22:20 +00:00
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}
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2015-05-01 22:35:49 +00:00
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}
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}
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2019-01-20 15:15:00 +00:00
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fn parent_node_is_if_expr<'a, 'b>(expr: &Expr, cx: &LateContext<'a, 'b>) -> bool {
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let parent_id = cx.tcx.hir().get_parent_node(expr.id);
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let parent_node = cx.tcx.hir().get(parent_id);
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if let rustc::hir::Node::Expr(e) = parent_node {
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if let ExprKind::If(_,_,_) = e.node {
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2019-01-21 10:14:34 +00:00
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return true;
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2019-01-20 15:15:00 +00:00
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}
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}
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false
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}
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2017-08-09 07:30:56 +00:00
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#[derive(Copy, Clone)]
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2016-02-09 19:10:22 +00:00
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pub struct BoolComparison;
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impl LintPass for BoolComparison {
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fn get_lints(&self) -> LintArray {
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lint_array!(BOOL_COMPARISON)
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}
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}
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2016-12-07 12:13:40 +00:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoolComparison {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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2018-10-29 21:23:45 +00:00
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if in_macro(e.span) {
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return;
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}
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2018-11-02 11:12:14 +00:00
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2018-11-30 13:21:11 +00:00
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if let ExprKind::Binary(Spanned { node, .. }, ..) = e.node {
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2018-12-07 00:50:16 +00:00
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let ignore_case = None::<(fn(_) -> _, &str)>;
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let ignore_no_literal = None::<(fn(_, _) -> _, &str)>;
|
2018-11-30 13:21:11 +00:00
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match node {
|
2018-12-07 00:50:16 +00:00
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BinOpKind::Eq => {
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let true_case = Some((|h| h, "equality checks against true are unnecessary"));
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let false_case = Some((
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|h: Sugg<'_>| !h,
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"equality checks against false can be replaced by a negation",
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));
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check_comparison(cx, e, true_case, false_case, true_case, false_case, ignore_no_literal)
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},
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BinOpKind::Ne => {
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let true_case = Some((
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|h: Sugg<'_>| !h,
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"inequality checks against true can be replaced by a negation",
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));
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let false_case = Some((|h| h, "inequality checks against false are unnecessary"));
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check_comparison(cx, e, true_case, false_case, true_case, false_case, ignore_no_literal)
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},
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BinOpKind::Lt => check_comparison(
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2018-11-30 13:21:11 +00:00
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cx,
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e,
|
2018-12-07 00:50:16 +00:00
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ignore_case,
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Some((|h| h, "greater than checks against false are unnecessary")),
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Some((
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|h: Sugg<'_>| !h,
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"less than comparison against true can be replaced by a negation",
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)),
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ignore_case,
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Some((
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2018-12-17 18:32:24 +00:00
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|l: Sugg<'_>, r: Sugg<'_>| (!l).bit_and(&r),
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2018-12-07 00:50:16 +00:00
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"order comparisons between booleans can be simplified",
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)),
|
2018-11-30 13:21:11 +00:00
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),
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2018-12-07 00:50:16 +00:00
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BinOpKind::Gt => check_comparison(
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2018-11-30 13:21:11 +00:00
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cx,
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e,
|
2018-12-07 00:50:16 +00:00
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Some((
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|h: Sugg<'_>| !h,
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"less than comparison against true can be replaced by a negation",
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)),
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ignore_case,
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ignore_case,
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Some((|h| h, "greater than checks against false are unnecessary")),
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Some((
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2018-12-17 18:32:24 +00:00
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|l: Sugg<'_>, r: Sugg<'_>| l.bit_and(&(!r)),
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2018-12-07 00:50:16 +00:00
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"order comparisons between booleans can be simplified",
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)),
|
2018-11-30 13:21:11 +00:00
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),
|
2018-10-29 21:23:45 +00:00
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_ => (),
|
2016-02-09 19:10:22 +00:00
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}
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}
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}
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}
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2018-11-30 13:21:11 +00:00
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fn check_comparison<'a, 'tcx>(
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cx: &LateContext<'a, 'tcx>,
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e: &'tcx Expr,
|
2018-12-07 00:50:16 +00:00
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left_true: Option<(impl FnOnce(Sugg<'a>) -> Sugg<'a>, &str)>,
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left_false: Option<(impl FnOnce(Sugg<'a>) -> Sugg<'a>, &str)>,
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right_true: Option<(impl FnOnce(Sugg<'a>) -> Sugg<'a>, &str)>,
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right_false: Option<(impl FnOnce(Sugg<'a>) -> Sugg<'a>, &str)>,
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no_literal: Option<(impl FnOnce(Sugg<'a>, Sugg<'a>) -> Sugg<'a>, &str)>,
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2018-11-30 13:21:11 +00:00
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) {
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use self::Expression::*;
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if let ExprKind::Binary(_, ref left_side, ref right_side) = e.node {
|
2018-12-07 00:50:16 +00:00
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|
let mut applicability = Applicability::MachineApplicable;
|
2018-11-30 13:21:11 +00:00
|
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match (fetch_bool_expr(left_side), fetch_bool_expr(right_side)) {
|
2018-12-07 00:50:16 +00:00
|
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|
(Bool(true), Other) => left_true.map_or((), |(h, m)| {
|
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suggest_bool_comparison(cx, e, right_side, applicability, m, h)
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}),
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(Other, Bool(true)) => right_true.map_or((), |(h, m)| {
|
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|
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suggest_bool_comparison(cx, e, left_side, applicability, m, h)
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|
}),
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|
(Bool(false), Other) => left_false.map_or((), |(h, m)| {
|
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|
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suggest_bool_comparison(cx, e, right_side, applicability, m, h)
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|
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|
}),
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|
(Other, Bool(false)) => right_false.map_or((), |(h, m)| {
|
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|
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suggest_bool_comparison(cx, e, left_side, applicability, m, h)
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|
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|
}),
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|
(Other, Other) => no_literal.map_or((), |(h, m)| {
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|
|
|
let (l_ty, r_ty) = (cx.tables.expr_ty(left_side), cx.tables.expr_ty(right_side));
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|
|
|
if l_ty.is_bool() && r_ty.is_bool() {
|
|
|
|
let left_side = Sugg::hir_with_applicability(cx, left_side, "..", &mut applicability);
|
|
|
|
let right_side = Sugg::hir_with_applicability(cx, right_side, "..", &mut applicability);
|
|
|
|
span_lint_and_sugg(
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|
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|
cx,
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|
|
BOOL_COMPARISON,
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|
|
|
e.span,
|
|
|
|
m,
|
|
|
|
"try simplifying it as shown",
|
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|
|
h(left_side, right_side).to_string(),
|
|
|
|
applicability,
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|
|
|
)
|
|
|
|
}
|
|
|
|
}),
|
2018-11-30 13:21:11 +00:00
|
|
|
_ => (),
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
fn suggest_bool_comparison<'a, 'tcx>(
|
|
|
|
cx: &LateContext<'a, 'tcx>,
|
|
|
|
e: &'tcx Expr,
|
|
|
|
expr: &Expr,
|
|
|
|
mut applicability: Applicability,
|
|
|
|
message: &str,
|
2018-12-07 00:50:16 +00:00
|
|
|
conv_hint: impl FnOnce(Sugg<'a>) -> Sugg<'a>,
|
2018-11-30 13:21:11 +00:00
|
|
|
) {
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|
|
|
let hint = Sugg::hir_with_applicability(cx, expr, "..", &mut applicability);
|
|
|
|
span_lint_and_sugg(
|
|
|
|
cx,
|
|
|
|
BOOL_COMPARISON,
|
|
|
|
e.span,
|
|
|
|
message,
|
|
|
|
"try simplifying it as shown",
|
|
|
|
conv_hint(hint).to_string(),
|
|
|
|
applicability,
|
|
|
|
);
|
|
|
|
}
|
|
|
|
|
2016-03-14 15:41:41 +00:00
|
|
|
enum Expression {
|
|
|
|
Bool(bool),
|
|
|
|
RetBool(bool),
|
|
|
|
Other,
|
|
|
|
}
|
|
|
|
|
|
|
|
fn fetch_bool_block(block: &Block) -> Expression {
|
|
|
|
match (&*block.stmts, block.expr.as_ref()) {
|
2016-06-10 17:47:10 +00:00
|
|
|
(&[], Some(e)) => fetch_bool_expr(&**e),
|
2018-11-27 20:14:15 +00:00
|
|
|
(&[ref e], None) => {
|
|
|
|
if let StmtKind::Semi(ref e, _) = e.node {
|
|
|
|
if let ExprKind::Ret(_) = e.node {
|
|
|
|
fetch_bool_expr(&**e)
|
|
|
|
} else {
|
|
|
|
Expression::Other
|
|
|
|
}
|
2016-03-14 15:41:41 +00:00
|
|
|
} else {
|
|
|
|
Expression::Other
|
|
|
|
}
|
2016-12-20 17:21:30 +00:00
|
|
|
},
|
2016-03-14 15:41:41 +00:00
|
|
|
_ => Expression::Other,
|
2016-01-04 04:26:12 +00:00
|
|
|
}
|
2015-05-01 22:35:49 +00:00
|
|
|
}
|
2015-08-11 18:22:20 +00:00
|
|
|
|
2016-03-14 15:41:41 +00:00
|
|
|
fn fetch_bool_expr(expr: &Expr) -> Expression {
|
2015-08-21 18:44:48 +00:00
|
|
|
match expr.node {
|
2018-07-12 07:30:57 +00:00
|
|
|
ExprKind::Block(ref block, _) => fetch_bool_block(block),
|
2018-11-27 20:14:15 +00:00
|
|
|
ExprKind::Lit(ref lit_ptr) => {
|
|
|
|
if let LitKind::Bool(value) = lit_ptr.node {
|
|
|
|
Expression::Bool(value)
|
|
|
|
} else {
|
|
|
|
Expression::Other
|
|
|
|
}
|
2016-12-20 17:21:30 +00:00
|
|
|
},
|
2018-07-12 07:30:57 +00:00
|
|
|
ExprKind::Ret(Some(ref expr)) => match fetch_bool_expr(expr) {
|
2017-09-05 09:33:04 +00:00
|
|
|
Expression::Bool(value) => Expression::RetBool(value),
|
|
|
|
_ => Expression::Other,
|
2016-12-20 17:21:30 +00:00
|
|
|
},
|
2016-03-14 15:41:41 +00:00
|
|
|
_ => Expression::Other,
|
2015-08-11 18:22:20 +00:00
|
|
|
}
|
2015-05-01 22:35:49 +00:00
|
|
|
}
|