syntax_data: {"ast_node_type":"variable","tokens":[{"end":68,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 //     fields. We don't want `let x: ();` to compile
context_before:                 // (c) handle the case where the type Foo has no
context_after:                 //     to the same MIR as `let x = ();`.