Part of issue #645.

Part of issue #645.

The escaped caret was taken for a negated character class.  This caused test-data/arith1.zsh
to XPass: the arithmetic expansion was consumed by the 'while' loop.

This is not perfect: we don't try to detect cases such as «$((ls); (ls))»,
which look like arithmetic expansions but are in fact command substitutions.

Fixes part of #607.

Introduces #704.

Fixes #694.

Fixes #583.

Fixes #582.

No functional change.

Fixes #630.

Fixes #676.

Computing ${#array} is O(N), whereas checking 0 is O(1).

Uses the infrastructure added in the previous commit.

Fixes #678.

This prevents the baz pattern match from being attempted whenever the
bar pattern match was tried and failed.

No functional change.

Before this commit, the test was unable to XPass, since there is no
highlighting style called "normal".

Before this commit, the command word was highlighted as "unknown-token"
not because alias loops are invalid, as a comment incorrectly claimed,
but because the command word «a» resolved to a «b» that was ineligible
for being expanded as an alias, and there was no function/builtin/etc.
called "b".

Add a function "b" to demonstrate that alias loops are valid.  I've also
filed issue #695 about the overloading of "unknown-token".

Fixes #501.

Fixes #616 (the original form; not the form in
test-data/alias-comment1.zsh which is now considered o be #677 (see
previous commit for details)).

Fixes a latent bug in test-data/always2.zsh.

No user-visible effect, and therefore, no changelog entry.

See https://github.com/zsh-users/zsh-syntax-highlighting/issues/677#issuecomment-599225740 for details.

(In particular, there's already another test that calls itself #616.)

Fixes #651.

Fixes the test added in the penultimate (grandparent) commit.

Used by the next commit.

- pipes (issue #651)
- semicolons
- literal newlines
  (also discussed on #651)

Fixes #646.

It is fixed in the next commit.