src/tools/clippy/clippy_lints/src/unit_types/let_unit_value.rs

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