Add some more AST node size assertions.

There is some redundancy here, but the extra assertions make it easier
to keep track of relative things, e.g. `ExprKind` is the biggest part
of `Expr`.

Author: nnethercote

compiler/rustc_ast/src/ast.rs

@@ -3035,6 +3035,7 @@ mod size_asserts {
     static_assert_size!(Attribute, 152);
     static_assert_size!(Block, 48);
     static_assert_size!(Expr, 104);
+    static_assert_size!(ExprKind, 72);
     static_assert_size!(Fn, 192);
     static_assert_size!(ForeignItem, 160);
     static_assert_size!(ForeignItemKind, 72);
@@ -3044,9 +3045,13 @@ mod size_asserts {
     static_assert_size!(Item, 200);
     static_assert_size!(ItemKind, 112);
     static_assert_size!(Lit, 48);
+    static_assert_size!(LitKind, 24);
     static_assert_size!(Pat, 120);
+    static_assert_size!(PatKind, 96);
     static_assert_size!(Path, 40);
     static_assert_size!(PathSegment, 24);
     static_assert_size!(Stmt, 32);
+    static_assert_size!(StmtKind, 16);
     static_assert_size!(Ty, 96);
+    static_assert_size!(TyKind, 72);
 }