Fix parsing of indented modules #63
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Indented modules weren't parsing due to an error in how the recovery routine derived the current indent column. Recovery derived the indent from the layout stack in the token stream. This layout stack, however, represents the stack after the current token. This is usually OK, but has an edge case when the current token is TokLayoutEnd. For the purposes of recovery, we want TokLayoutEnd's column to represent the current indent. In the specific case of top-level module/declaration parsing, we invoke recovery for all declarations, which are also wrapped in a `many`. Indentation recovery eats any token indented more than the current indentation. Once we get to a TokLayoutEnd for the module, which closes the top-level `where` block, the current layout stack is only LytRoot, so the indent defaults to 0. Because the module is also indented to 0, this will fail the recovery predicate as we expect, resulting in a correct module parse. When the indent is more than 0, it will satisfy the recovery predicate (since TokLayoutEnd col is greater than 0), eating the TokLayoutEnd token. Module parsing would then fail due to an unexpected EOF (where TokLayoutEnd was expected). When take the TokLayoutEnd column into account when deriving the current indent, then the recovery predicate will fail as expected, resulting in a correct parse. Fixes #56
While there are no currently known bugs due to this, the consumed semantics are implemented incorrectly. Consumed should act as a Semigroup across binds (Writer).
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