src/tools/clippy/clippy_lints/src/semicolon_if_nothing_returned.rs

   1 use crate::rustc_lint::LintContext;
   2 use clippy_utils::diagnostics::span_lint_and_sugg;
   3 use clippy_utils::source::snippet_with_macro_callsite;
   4 use clippy_utils::sugg;
   5 use if_chain::if_chain;
   6 use rustc_errors::Applicability;
   7 use rustc_hir::{Block, ExprKind};
   8 use rustc_lint::{LateContext, LateLintPass};
   9 use rustc_session::{declare_lint_pass, declare_tool_lint};
  10
  11 declare_clippy_lint! {
  12     /// ### What it does
  13     /// Looks for blocks of expressions and fires if the last expression returns
  14     /// `()` but is not followed by a semicolon.
  15     ///
  16     /// ### Why is this bad?
  17     /// The semicolon might be optional but when extending the block with new
  18     /// code, it doesn't require a change in previous last line.
  19     ///
  20     /// ### Example
  21     /// ```rust
  22     /// fn main() {
  23     ///     println!("Hello world")
  24     /// }
  25     /// ```
  26     /// Use instead:
  27     /// ```rust
  28     /// fn main() {
  29     ///     println!("Hello world");
  30     /// }
  31     /// ```
  32     #[clippy::version = "1.52.0"]
  33     pub SEMICOLON_IF_NOTHING_RETURNED,
  34     pedantic,
  35     "add a semicolon if nothing is returned"
  36 }
  37
  38 declare_lint_pass!(SemicolonIfNothingReturned => [SEMICOLON_IF_NOTHING_RETURNED]);
  39
  40 impl<'tcx> LateLintPass<'tcx> for SemicolonIfNothingReturned {
  41     fn check_block(&mut self, cx: &LateContext<'tcx>, block: &'tcx Block<'tcx>) {
  42         if_chain! {
  43             if !block.span.from_expansion();
  44             if let Some(expr) = block.expr;
  45             let t_expr = cx.typeck_results().expr_ty(expr);
  46             if t_expr.is_unit();
  47             if let snippet = snippet_with_macro_callsite(cx, expr.span, "}");
  48             if !snippet.ends_with('}') && !snippet.ends_with(';');
  49             if cx.sess().source_map().is_multiline(block.span);
  50             then {
  51                 // filter out the desugared `for` loop
  52                 if let ExprKind::DropTemps(..) = &expr.kind {
  53                     return;
  54                 }
  55
  56                 let sugg = sugg::Sugg::hir_with_macro_callsite(cx, expr, "..");
  57                 let suggestion = format!("{sugg};");
  58                 span_lint_and_sugg(
  59                     cx,
  60                     SEMICOLON_IF_NOTHING_RETURNED,
  61                     expr.span.source_callsite(),
  62                     "consider adding a `;` to the last statement for consistent formatting",
  63                     "add a `;` here",
  64                     suggestion,
  65                     Applicability::MaybeIncorrect,
  66                 );
  67             }
  68         }
  69     }
  70 }