Don't lint on redundant semicolons after item statements

This preserves the current lint behavior for now.

Linting after item statements currently prevents the compiler from bootstrapping.
Fixing this is blocked on fixing this upstream in Cargo, and bumping the Cargo
submodule.

compiler/rustc_lint/src/redundant_semicolon.rs

@@ -28,25 +28,40 @@ declare_lint_pass!(RedundantSemicolons => [REDUNDANT_SEMICOLONS]);
 
 impl EarlyLintPass for RedundantSemicolons {
     fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
+        let mut after_item_stmt = false;
         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),
+                (_, seq) => {
+                    maybe_lint_redundant_semis(cx, seq, after_item_stmt);
+                    after_item_stmt = matches!(stmt.kind, StmtKind::Item(_));
+                }
             }
         }
-        maybe_lint_redundant_semis(cx, &mut seq);
+        maybe_lint_redundant_semis(cx, &mut seq, after_item_stmt);
     }
 }
 
-fn maybe_lint_redundant_semis(cx: &EarlyContext<'_>, seq: &mut Option<(Span, bool)>) {
+fn maybe_lint_redundant_semis(
+    cx: &EarlyContext<'_>,
+    seq: &mut Option<(Span, bool)>,
+    after_item_stmt: 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;
         }
+
+        // FIXME: Lint on semicolons after item statements
+        // once doing so doesn't break bootstrapping
+        if after_item_stmt {
+            return;
+        }
+
         cx.struct_span_lint(REDUNDANT_SEMICOLONS, span, |lint| {
             let (msg, rem) = if multiple {
                 ("unnecessary trailing semicolons", "remove these semicolons")

src/test/ui/lint/redundant-semicolon/item-stmt-semi.rs

@@ -0,0 +1,10 @@
+// check-pass
+// This test should stop compiling
+// we decide to enable this lint for item statements.
+
+#![deny(redundant_semicolons)]
+
+fn main() {
+    fn inner() {};
+    struct Bar {};
+}