clippy_lints/src/unit_types/let_unit_value.rs

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use clippy_utils::higher;
   3 use clippy_utils::source::snippet_with_macro_callsite;
   4 use rustc_errors::Applicability;
   5 use rustc_hir::{Stmt, StmtKind};
   6 use rustc_lint::{LateContext, LintContext};
   7 use rustc_middle::lint::in_external_macro;
   8
   9 use super::LET_UNIT_VALUE;
  10
  11 pub(super) fn check(cx: &LateContext<'_>, stmt: &Stmt<'_>) {
  12     if let StmtKind::Local(ref local) = stmt.kind {
  13         if cx.typeck_results().pat_ty(&local.pat).is_unit() {
  14             if in_external_macro(cx.sess(), stmt.span) || local.pat.span.from_expansion() {
  15                 return;
  16             }
  17             if higher::is_from_for_desugar(local) {
  18                 return;
  19             }
  20             span_lint_and_then(
  21                 cx,
  22                 LET_UNIT_VALUE,
  23                 stmt.span,
  24                 "this let-binding has unit value",
  25                 |diag| {
  26                     if let Some(expr) = &local.init {
  27                         let snip = snippet_with_macro_callsite(cx, expr.span, "()");
  28                         diag.span_suggestion(
  29                             stmt.span,
  30                             "omit the `let` binding",
  31                             format!("{};", snip),
  32                             Applicability::MachineApplicable, // snippet
  33                         );
  34                     }
  35                 },
  36             );
  37         }
  38     }
  39 }