Rollup merge of #34436 - jseyfried:no_block_expr, r=eddyb

To allow these braced macro invocation, this PR removes the optional expression from `ast::Block` and instead uses a `StmtKind::Expr` at the end of the statement list.

Currently, braced macro invocations in blocks can expand into statements (and items) except when they are last in a block, in which case they can only expand into expressions.

For example,
```rust
macro_rules! make_stmt {
    () => { let x = 0; }
}

fn f() {
    make_stmt! {} //< This is OK...
    let x = 0; //< ... unless this line is commented out.
}
```

Fixes #34418.

1 files changed, 4 insertions, 6 deletions

diff --git a/src/libsyntax_ext/deriving/clone.rs b/src/libsyntax_ext/deriving/clone.rs
index 00714002875..1e47ebb8583 100644
--- a/src/libsyntax_ext/deriving/clone.rs
+++ b/src/libsyntax_ext/deriving/clone.rs
@@ -145,12 +145,10 @@ fn cs_clone(
 
     match mode {
         Mode::Shallow => {
-            cx.expr_block(cx.block(trait_span,
-                                   all_fields.iter()
-                                             .map(subcall)
-                                             .map(|e| cx.stmt_expr(e))
-                                             .collect(),
-                                   Some(cx.expr_deref(trait_span, cx.expr_self(trait_span)))))
+            let mut stmts: Vec<_> =
+                all_fields.iter().map(subcall).map(|e| cx.stmt_expr(e)).collect();
+            stmts.push(cx.stmt_expr(cx.expr_deref(trait_span, cx.expr_self(trait_span))));
+            cx.expr_block(cx.block(trait_span, stmts))
         }
         Mode::Deep => {
             match *vdata {