Match and Pattern compilation checklist

This is a brain dump of the various bits of match expressions that we
aren't currently compiling. Probably incomplete.

Patterns https://doc.rust-lang.org/reference/patterns.html

• Literal Patterns 1, 'a'
• Identifier Patterns and bindings e @ 1..=5
• Wildcard Patterns _
• Rest Patterns ..
• Range Patterns 1..=5
• Reference Patterns
• Struct Patterns
• TupleStruct Patterns
• Tuple Patterns
  Done? at least in match expressions
• Grouped Patterns &(0..=5)
• Path Patterns
• Or-patterns Foo::A | Foo::B
• Slice Patterns [a, b, _]

Match to-dos (done items not listed)

• path-to-tuple scrutinee #1478 is one fix)
• struct scrutinee (i.e. non-enum ADT)
• nested tuple scrutinee match ((Foo::A, 1), ('c', Foo::B))
• match arm guards Some(x) if x < 10