Only -@ and +@ cannot be sent.
Added specs for Statement#initialize.
Added specs for Statement#to_sql.
Added specs for Clause#to_sql.
Speced BinaryExpr.
Speced UnaryExpr.
Changed how Injection#and / Injection#or nest expressions.
Began specing Injection.
Added Emitter#emit_clauses.
Added SQL::Emittable.
Added Fields#respond_to_missing?
Define Fields#to_ary so we can puts SQL objects.
Removed requirements to avoid circular requirement issues.
Speced Injection#to_sql.
Added requires to ronin/sql/program.