[[var]] wikilink font-lock rule collides with Datalog/Datomic relation-binding syntax

[daveliepmann]

Affected mode

clojure-mode

Expected behavior

Datalog vars in [[double square brackets]] get the same syntax highlighting as elsewhere.

Actual behavior

The [[var]] docstring-wikilink font-lock rule (added in #496) matches any
[[symbol]]-shaped text regardless of syntactic context — it isn't gated by
syntax-ppss to comments/docstrings/strings. This causes false-positive
highlighting in live Datalog/Datomic code, where [[var]] is legitimate
binding syntax (a relation binding, as opposed to [var] for a tuple binding
or [var ...] for a collection binding).

Version: clojure-mode 20250527.840 (current master exhibits the same
behavior as of 2026-09-23).

Suggested fix: gate the [[var]] (and backtick `code`) rules on
(nth 3 (syntax-ppss (match-beginning 0))) or (nth 4 ...) so they only
fire inside strings/comments, matching their intended use for docstrings.

Steps to reproduce

Based on Datomic docs:

(d/q '[:find ?track ?name ?duration
       :where
       [(q '[:find (min ?duration)
             :where [_ :track/duration ?duration]]
           $) [[?duration]]] ; <--------------------- this guy ain't right
       [?track :track/duration ?duration]
       [?track :track/name ?name]]
     db)

All five occurrences of ?duration are the same logic variable, but the one
inside [[?duration]] gets font-lock-constant-face (matched by the
wikilink rule at clojure-mode.el:1229-1232) while the other four get the
default face — inconsistent highlighting with no semantic basis.

Reproducible with emacs -Q

• I've reproduced this with emacs -Q

clojure-mode version

20250527.840

Emacs version

GNU Emacs 30.2.50 (build 1, aarch64-apple-darwin24.6.0, Carbon Version 170 AppKit 2575.7) of 2026-03-09

Operating system

macOS Sequoia 15.8