Updated pattern match documents

[John Rose]

On Oct 1, 2018, at 9:48 PM, Tagir Valeev <amaembo at gmail.com> wrote:
> 
> I tried to think how to break this. Some interesting cases could arise
> if nullable type patterns are allowed for instanceof (which could be
> useful sometimes):

Yes, the trailing structure of the pattern gets tangled up with the
right-context of a typical expression.

One way to fix that is to make "x instanceof P" have a much lower
precedence than "x instanceof C", where C is a name and P is a
pattern which is not a name.

We don't have a precedent grammar, but we can demand that the
right-context of "x instanceof P" is comma, close paren, or the like.
Like this:

AssignmentExpression:
  ConditionalExpression
  PatternMatchExpression
  Assignment

Or this:

Expression:
  LambdaExpression 
  PatternMatchExpression
  AssignmentExpression

The practical effect of this will be to force people to put parentheses
around "x instanceof P" when there is ambiguity.

— John
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