[meta] Expressions

[Hywan]

Address #11.

Specification

https://github.com/php/php-langspec/blob/master/spec/19-grammar.md#expressions

Progression

• [x] Primary expressions,
• [ ] Postfix operators,
• [ ] Unary operators,
• [ ] Assignment operators:
  • [ ] Conditional operator,
    • [x] instanceof operator,
    • [x] Multiplicative operators,
    • [x] Additive operators,
    • [x] Bitwise shift operators,
    • [x] Relational operators,
    • [x] Equality operators,
    • [x] Bitwise logical operators,
    • [x] Logical operators (form 1),
    • [ ] Logical operators (form 2),
  • [x] Coalesce operator,
• [ ] yield operator,
• [ ] Script inclusion operators,
• [ ] Constants expressions.