1 files changed, 58 insertions, 0 deletions
diff --git a/compiler/rustc_lint/src/redundant_semicolon.rs b/compiler/rustc_lint/src/redundant_semicolon.rs
new file mode 100644
index 000000000..26f413453
--- /dev/null
+++ b/compiler/rustc_lint/src/redundant_semicolon.rs
@@ -0,0 +1,58 @@
+use crate::{EarlyContext, EarlyLintPass, LintContext};
+use rustc_ast::{Block, StmtKind};
+use rustc_errors::{fluent, Applicability};
+use rustc_span::Span;
+
+declare_lint! {
+    /// The `redundant_semicolons` lint detects unnecessary trailing
+    /// semicolons.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// let _ = 123;;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Extra semicolons are not needed, and may be removed to avoid confusion
+    /// and visual clutter.
+    pub REDUNDANT_SEMICOLONS,
+    Warn,
+    "detects unnecessary trailing semicolons"
+}
+
+declare_lint_pass!(RedundantSemicolons => [REDUNDANT_SEMICOLONS]);
+
+impl EarlyLintPass for RedundantSemicolons {
+    fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
+        let mut seq = None;
+        for stmt in block.stmts.iter() {
+            match (&stmt.kind, &mut seq) {
+                (StmtKind::Empty, None) => seq = Some((stmt.span, false)),
+                (StmtKind::Empty, Some(seq)) => *seq = (seq.0.to(stmt.span), true),
+                (_, seq) => maybe_lint_redundant_semis(cx, seq),
+            }
+        }
+        maybe_lint_redundant_semis(cx, &mut seq);
+    }
+}
+
+fn maybe_lint_redundant_semis(cx: &EarlyContext<'_>, seq: &mut Option<(Span, bool)>) {
+    if let Some((span, multiple)) = seq.take() {
+        // FIXME: Find a better way of ignoring the trailing
+        // semicolon from macro expansion
+        if span == rustc_span::DUMMY_SP {
+            return;
+        }
+
+        cx.struct_span_lint(REDUNDANT_SEMICOLONS, span, |lint| {
+            lint.build(fluent::lint::redundant_semicolons)
+                .set_arg("multiple", multiple)
+                .span_suggestion(span, fluent::lint::suggestion, "", Applicability::MaybeIncorrect)
+                .emit();
+        });
+    }
+}