505 lines
18 KiB
Rust
505 lines
18 KiB
Rust
use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
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use clippy_utils::source::snippet_opt;
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use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
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use clippy_utils::{eq_expr_value, get_trait_def_id, in_macro, paths};
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use if_chain::if_chain;
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use rustc_ast::ast::LitKind;
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use rustc_errors::Applicability;
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use rustc_hir::intravisit::{walk_expr, FnKind, NestedVisitorMap, Visitor};
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use rustc_hir::{BinOpKind, Body, Expr, ExprKind, FnDecl, HirId, UnOp};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::hir::map::Map;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::source_map::Span;
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use rustc_span::sym;
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declare_clippy_lint! {
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/// **What it does:** Checks for boolean expressions that can be written more
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/// concisely.
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///
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/// **Why is this bad?** Readability of boolean expressions suffers from
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/// unnecessary duplication.
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///
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/// **Known problems:** Ignores short circuiting behavior of `||` and
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/// `&&`. Ignores `|`, `&` and `^`.
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///
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/// **Example:**
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/// ```ignore
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/// if a && true // should be: if a
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/// if !(a == b) // should be: if a != b
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/// ```
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pub NONMINIMAL_BOOL,
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complexity,
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"boolean expressions that can be written more concisely"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for boolean expressions that contain terminals that
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/// can be eliminated.
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///
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/// **Why is this bad?** This is most likely a logic bug.
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///
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/// **Known problems:** Ignores short circuiting behavior.
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///
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/// **Example:**
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/// ```ignore
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/// if a && b || a { ... }
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/// ```
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/// The `b` is unnecessary, the expression is equivalent to `if a`.
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pub LOGIC_BUG,
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correctness,
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"boolean expressions that contain terminals which can be eliminated"
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}
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// For each pairs, both orders are considered.
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const METHODS_WITH_NEGATION: [(&str, &str); 2] = [("is_some", "is_none"), ("is_err", "is_ok")];
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declare_lint_pass!(NonminimalBool => [NONMINIMAL_BOOL, LOGIC_BUG]);
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impl<'tcx> LateLintPass<'tcx> for NonminimalBool {
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fn check_fn(
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&mut self,
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cx: &LateContext<'tcx>,
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_: FnKind<'tcx>,
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_: &'tcx FnDecl<'_>,
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body: &'tcx Body<'_>,
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_: Span,
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_: HirId,
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) {
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NonminimalBoolVisitor { cx }.visit_body(body)
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}
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}
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struct NonminimalBoolVisitor<'a, 'tcx> {
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cx: &'a LateContext<'tcx>,
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}
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use quine_mc_cluskey::Bool;
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struct Hir2Qmm<'a, 'tcx, 'v> {
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terminals: Vec<&'v Expr<'v>>,
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cx: &'a LateContext<'tcx>,
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}
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impl<'a, 'tcx, 'v> Hir2Qmm<'a, 'tcx, 'v> {
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fn extract(&mut self, op: BinOpKind, a: &[&'v Expr<'_>], mut v: Vec<Bool>) -> Result<Vec<Bool>, String> {
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for a in a {
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if let ExprKind::Binary(binop, lhs, rhs) = &a.kind {
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if binop.node == op {
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v = self.extract(op, &[lhs, rhs], v)?;
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continue;
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}
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}
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v.push(self.run(a)?);
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}
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Ok(v)
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}
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fn run(&mut self, e: &'v Expr<'_>) -> Result<Bool, String> {
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fn negate(bin_op_kind: BinOpKind) -> Option<BinOpKind> {
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match bin_op_kind {
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BinOpKind::Eq => Some(BinOpKind::Ne),
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BinOpKind::Ne => Some(BinOpKind::Eq),
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BinOpKind::Gt => Some(BinOpKind::Le),
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BinOpKind::Ge => Some(BinOpKind::Lt),
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BinOpKind::Lt => Some(BinOpKind::Ge),
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BinOpKind::Le => Some(BinOpKind::Gt),
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_ => None,
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}
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}
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// prevent folding of `cfg!` macros and the like
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if !e.span.from_expansion() {
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match &e.kind {
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ExprKind::Unary(UnOp::Not, inner) => return Ok(Bool::Not(box self.run(inner)?)),
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ExprKind::Binary(binop, lhs, rhs) => match &binop.node {
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BinOpKind::Or => {
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return Ok(Bool::Or(self.extract(BinOpKind::Or, &[lhs, rhs], Vec::new())?));
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},
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BinOpKind::And => {
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return Ok(Bool::And(self.extract(BinOpKind::And, &[lhs, rhs], Vec::new())?));
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},
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_ => (),
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},
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ExprKind::Lit(lit) => match lit.node {
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LitKind::Bool(true) => return Ok(Bool::True),
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LitKind::Bool(false) => return Ok(Bool::False),
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_ => (),
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},
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_ => (),
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}
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}
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for (n, expr) in self.terminals.iter().enumerate() {
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if eq_expr_value(self.cx, e, expr) {
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#[allow(clippy::cast_possible_truncation)]
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return Ok(Bool::Term(n as u8));
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}
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if_chain! {
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if let ExprKind::Binary(e_binop, e_lhs, e_rhs) = &e.kind;
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if implements_ord(self.cx, e_lhs);
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if let ExprKind::Binary(expr_binop, expr_lhs, expr_rhs) = &expr.kind;
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if negate(e_binop.node) == Some(expr_binop.node);
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if eq_expr_value(self.cx, e_lhs, expr_lhs);
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if eq_expr_value(self.cx, e_rhs, expr_rhs);
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then {
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#[allow(clippy::cast_possible_truncation)]
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return Ok(Bool::Not(Box::new(Bool::Term(n as u8))));
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}
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}
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}
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let n = self.terminals.len();
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self.terminals.push(e);
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if n < 32 {
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#[allow(clippy::cast_possible_truncation)]
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Ok(Bool::Term(n as u8))
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} else {
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Err("too many literals".to_owned())
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}
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}
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}
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struct SuggestContext<'a, 'tcx, 'v> {
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terminals: &'v [&'v Expr<'v>],
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cx: &'a LateContext<'tcx>,
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output: String,
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}
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impl<'a, 'tcx, 'v> SuggestContext<'a, 'tcx, 'v> {
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fn recurse(&mut self, suggestion: &Bool) -> Option<()> {
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use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
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match suggestion {
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True => {
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self.output.push_str("true");
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},
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False => {
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self.output.push_str("false");
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},
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Not(inner) => match **inner {
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And(_) | Or(_) => {
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self.output.push('!');
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self.output.push('(');
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self.recurse(inner);
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self.output.push(')');
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},
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Term(n) => {
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let terminal = self.terminals[n as usize];
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if let Some(str) = simplify_not(self.cx, terminal) {
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self.output.push_str(&str)
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} else {
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self.output.push('!');
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let snip = snippet_opt(self.cx, terminal.span)?;
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self.output.push_str(&snip);
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}
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},
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True | False | Not(_) => {
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self.output.push('!');
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self.recurse(inner)?;
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},
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},
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And(v) => {
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for (index, inner) in v.iter().enumerate() {
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if index > 0 {
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self.output.push_str(" && ");
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}
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if let Or(_) = *inner {
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self.output.push('(');
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self.recurse(inner);
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self.output.push(')');
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} else {
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self.recurse(inner);
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}
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}
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},
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Or(v) => {
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for (index, inner) in v.iter().rev().enumerate() {
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if index > 0 {
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self.output.push_str(" || ");
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}
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self.recurse(inner);
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}
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},
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&Term(n) => {
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let snip = snippet_opt(self.cx, self.terminals[n as usize].span)?;
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self.output.push_str(&snip);
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},
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}
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Some(())
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}
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}
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fn simplify_not(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<String> {
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match &expr.kind {
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ExprKind::Binary(binop, lhs, rhs) => {
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if !implements_ord(cx, lhs) {
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return None;
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}
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match binop.node {
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BinOpKind::Eq => Some(" != "),
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BinOpKind::Ne => Some(" == "),
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BinOpKind::Lt => Some(" >= "),
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BinOpKind::Gt => Some(" <= "),
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BinOpKind::Le => Some(" > "),
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BinOpKind::Ge => Some(" < "),
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_ => None,
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}
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.and_then(|op| {
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Some(format!(
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"{}{}{}",
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snippet_opt(cx, lhs.span)?,
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op,
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snippet_opt(cx, rhs.span)?
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))
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})
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},
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ExprKind::MethodCall(path, _, args, _) if args.len() == 1 => {
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let type_of_receiver = cx.typeck_results().expr_ty(&args[0]);
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if !is_type_diagnostic_item(cx, type_of_receiver, sym::option_type)
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&& !is_type_diagnostic_item(cx, type_of_receiver, sym::result_type)
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{
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return None;
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}
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METHODS_WITH_NEGATION
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.iter()
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.cloned()
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.flat_map(|(a, b)| vec![(a, b), (b, a)])
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.find(|&(a, _)| {
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let path: &str = &path.ident.name.as_str();
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a == path
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})
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.and_then(|(_, neg_method)| Some(format!("{}.{}()", snippet_opt(cx, args[0].span)?, neg_method)))
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},
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_ => None,
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}
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}
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fn suggest(cx: &LateContext<'_>, suggestion: &Bool, terminals: &[&Expr<'_>]) -> String {
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let mut suggest_context = SuggestContext {
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terminals,
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cx,
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output: String::new(),
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};
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suggest_context.recurse(suggestion);
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suggest_context.output
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}
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fn simple_negate(b: Bool) -> Bool {
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use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
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match b {
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True => False,
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False => True,
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t @ Term(_) => Not(Box::new(t)),
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And(mut v) => {
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for el in &mut v {
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*el = simple_negate(::std::mem::replace(el, True));
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}
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Or(v)
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},
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Or(mut v) => {
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for el in &mut v {
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*el = simple_negate(::std::mem::replace(el, True));
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}
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And(v)
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},
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Not(inner) => *inner,
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}
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}
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#[derive(Default)]
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struct Stats {
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terminals: [usize; 32],
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negations: usize,
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ops: usize,
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}
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fn terminal_stats(b: &Bool) -> Stats {
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fn recurse(b: &Bool, stats: &mut Stats) {
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match b {
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True | False => stats.ops += 1,
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Not(inner) => {
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match **inner {
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And(_) | Or(_) => stats.ops += 1, // brackets are also operations
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_ => stats.negations += 1,
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}
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recurse(inner, stats);
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},
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And(v) | Or(v) => {
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stats.ops += v.len() - 1;
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for inner in v {
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recurse(inner, stats);
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}
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},
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&Term(n) => stats.terminals[n as usize] += 1,
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}
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}
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use quine_mc_cluskey::Bool::{And, False, Not, Or, Term, True};
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let mut stats = Stats::default();
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recurse(b, &mut stats);
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stats
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}
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impl<'a, 'tcx> NonminimalBoolVisitor<'a, 'tcx> {
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fn bool_expr(&self, e: &'tcx Expr<'_>) {
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let mut h2q = Hir2Qmm {
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terminals: Vec::new(),
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cx: self.cx,
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};
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if let Ok(expr) = h2q.run(e) {
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if h2q.terminals.len() > 8 {
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// QMC has exponentially slow behavior as the number of terminals increases
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// 8 is reasonable, it takes approximately 0.2 seconds.
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// See #825
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return;
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}
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let stats = terminal_stats(&expr);
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let mut simplified = expr.simplify();
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for simple in Bool::Not(Box::new(expr)).simplify() {
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match simple {
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Bool::Not(_) | Bool::True | Bool::False => {},
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_ => simplified.push(Bool::Not(Box::new(simple.clone()))),
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}
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let simple_negated = simple_negate(simple);
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if simplified.iter().any(|s| *s == simple_negated) {
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continue;
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}
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simplified.push(simple_negated);
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}
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let mut improvements = Vec::with_capacity(simplified.len());
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'simplified: for suggestion in &simplified {
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let simplified_stats = terminal_stats(suggestion);
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let mut improvement = false;
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for i in 0..32 {
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// ignore any "simplifications" that end up requiring a terminal more often
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// than in the original expression
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if stats.terminals[i] < simplified_stats.terminals[i] {
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continue 'simplified;
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}
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if stats.terminals[i] != 0 && simplified_stats.terminals[i] == 0 {
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span_lint_and_then(
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self.cx,
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LOGIC_BUG,
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e.span,
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"this boolean expression contains a logic bug",
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|diag| {
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diag.span_help(
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h2q.terminals[i].span,
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"this expression can be optimized out by applying boolean operations to the \
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outer expression",
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);
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diag.span_suggestion(
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e.span,
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"it would look like the following",
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suggest(self.cx, suggestion, &h2q.terminals),
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// nonminimal_bool can produce minimal but
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// not human readable expressions (#3141)
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Applicability::Unspecified,
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);
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},
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);
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// don't also lint `NONMINIMAL_BOOL`
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return;
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}
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// if the number of occurrences of a terminal decreases or any of the stats
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// decreases while none increases
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improvement |= (stats.terminals[i] > simplified_stats.terminals[i])
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|| (stats.negations > simplified_stats.negations && stats.ops == simplified_stats.ops)
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|| (stats.ops > simplified_stats.ops && stats.negations == simplified_stats.negations);
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}
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if improvement {
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improvements.push(suggestion);
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}
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}
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let nonminimal_bool_lint = |suggestions: Vec<_>| {
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span_lint_and_then(
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self.cx,
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NONMINIMAL_BOOL,
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e.span,
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"this boolean expression can be simplified",
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|diag| {
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diag.span_suggestions(
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e.span,
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"try",
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suggestions.into_iter(),
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// nonminimal_bool can produce minimal but
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// not human readable expressions (#3141)
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Applicability::Unspecified,
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);
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},
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);
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};
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if improvements.is_empty() {
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let mut visitor = NotSimplificationVisitor { cx: self.cx };
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visitor.visit_expr(e);
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} else {
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nonminimal_bool_lint(
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improvements
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.into_iter()
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.map(|suggestion| suggest(self.cx, suggestion, &h2q.terminals))
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.collect(),
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);
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}
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}
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}
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}
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impl<'a, 'tcx> Visitor<'tcx> for NonminimalBoolVisitor<'a, 'tcx> {
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type Map = Map<'tcx>;
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fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
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if in_macro(e.span) {
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return;
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}
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match &e.kind {
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ExprKind::Binary(binop, _, _) if binop.node == BinOpKind::Or || binop.node == BinOpKind::And => {
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self.bool_expr(e)
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},
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ExprKind::Unary(UnOp::Not, inner) => {
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if self.cx.typeck_results().node_types()[inner.hir_id].is_bool() {
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self.bool_expr(e);
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} else {
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walk_expr(self, e);
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}
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},
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_ => walk_expr(self, e),
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}
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}
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::None
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}
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}
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fn implements_ord<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> bool {
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let ty = cx.typeck_results().expr_ty(expr);
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get_trait_def_id(cx, &paths::ORD).map_or(false, |id| implements_trait(cx, ty, id, &[]))
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}
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struct NotSimplificationVisitor<'a, 'tcx> {
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cx: &'a LateContext<'tcx>,
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}
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impl<'a, 'tcx> Visitor<'tcx> for NotSimplificationVisitor<'a, 'tcx> {
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type Map = Map<'tcx>;
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fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
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if let ExprKind::Unary(UnOp::Not, inner) = &expr.kind {
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if let Some(suggestion) = simplify_not(self.cx, inner) {
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span_lint_and_sugg(
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self.cx,
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NONMINIMAL_BOOL,
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expr.span,
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"this boolean expression can be simplified",
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"try",
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suggestion,
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Applicability::MachineApplicable,
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);
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}
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}
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walk_expr(self, expr);
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}
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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|
NestedVisitorMap::None
|
|
}
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|
}
|