117 lines
3.7 KiB
Rust
117 lines
3.7 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::source::snippet_with_macro_callsite;
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use clippy_utils::{is_else_clause, is_lang_ctor, meets_msrv, msrvs};
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use if_chain::if_chain;
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use rustc_hir::LangItem::{OptionNone, OptionSome};
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_semver::RustcVersion;
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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declare_clippy_lint! {
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/// **What it does:** Checks for if-else that could be written to `bool::then`.
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///
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/// **Why is this bad?** Looks a little redundant. Using `bool::then` helps it have less lines of code.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// # let v = vec![0];
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/// let a = if v.is_empty() {
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/// println!("true!");
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/// Some(42)
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/// } else {
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/// None
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/// };
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/// ```
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///
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/// Could be written:
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///
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/// ```rust
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/// # let v = vec![0];
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/// let a = v.is_empty().then(|| {
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/// println!("true!");
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/// 42
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/// });
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/// ```
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pub IF_THEN_SOME_ELSE_NONE,
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restriction,
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"Finds if-else that could be written using `bool::then`"
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}
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pub struct IfThenSomeElseNone {
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msrv: Option<RustcVersion>,
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}
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impl IfThenSomeElseNone {
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#[must_use]
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pub fn new(msrv: Option<RustcVersion>) -> Self {
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Self { msrv }
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}
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}
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impl_lint_pass!(IfThenSomeElseNone => [IF_THEN_SOME_ELSE_NONE]);
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impl LateLintPass<'_> for IfThenSomeElseNone {
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fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'tcx Expr<'_>) {
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if !meets_msrv(self.msrv.as_ref(), &msrvs::BOOL_THEN) {
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return;
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}
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if in_external_macro(cx.sess(), expr.span) {
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return;
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}
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// We only care about the top-most `if` in the chain
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if is_else_clause(cx.tcx, expr) {
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return;
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}
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if_chain! {
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if let ExprKind::If(cond, then, Some(els)) = expr.kind;
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if let ExprKind::Block(then_block, _) = then.kind;
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if let Some(then_expr) = then_block.expr;
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if let ExprKind::Call(then_call, [then_arg]) = then_expr.kind;
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if let ExprKind::Path(ref then_call_qpath) = then_call.kind;
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if is_lang_ctor(cx, then_call_qpath, OptionSome);
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if let ExprKind::Block(els_block, _) = els.kind;
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if els_block.stmts.is_empty();
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if let Some(els_expr) = els_block.expr;
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if let ExprKind::Path(ref qpath) = els_expr.kind;
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if is_lang_ctor(cx, qpath, OptionNone);
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then {
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let cond_snip = snippet_with_macro_callsite(cx, cond.span, "[condition]");
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let cond_snip = if matches!(cond.kind, ExprKind::Unary(_, _) | ExprKind::Binary(_, _, _)) {
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format!("({})", cond_snip)
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} else {
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cond_snip.into_owned()
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};
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let arg_snip = snippet_with_macro_callsite(cx, then_arg.span, "");
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let closure_body = if then_block.stmts.is_empty() {
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arg_snip.into_owned()
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} else {
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format!("{{ /* snippet */ {} }}", arg_snip)
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};
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let help = format!(
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"consider using `bool::then` like: `{}.then(|| {})`",
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cond_snip,
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closure_body,
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);
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span_lint_and_help(
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cx,
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IF_THEN_SOME_ELSE_NONE,
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expr.span,
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"this could be simplified with `bool::then`",
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None,
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&help,
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);
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}
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}
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}
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extract_msrv_attr!(LateContext);
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}
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