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, 2 insertions, 2 deletions

diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index 7d454fe38cc..647e414a7fd 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -1332,8 +1332,8 @@ impl<'a> MethodDef<'a> {
             //  }
             let all_match = cx.expr_match(sp, match_arg, match_arms);
             let arm_expr = cx.expr_if(sp, discriminant_test, all_match, Some(arm_expr));
-            cx.expr_block(
-                cx.block_all(sp, index_let_stmts, Some(arm_expr)))
+            index_let_stmts.push(cx.stmt_expr(arm_expr));
+            cx.expr_block(cx.block(sp, index_let_stmts))
         } else if variants.is_empty() {
             // As an additional wrinkle, For a zero-variant enum A,
             // currently the compiler