TryStatement should use handler instead of handlers

[ariya]

The TryStatement node has changed according to estree/estree#1 from

interface TryStatement <: Statement {
    type: "TryStatement";
    block: BlockStatement;
    handlers: [ CatchClause ];
    guardedHandlers: [];
    finalizer: BlockStatement | null;
}

to

interface TryStatement <: Statement {
    type: "TryStatement";
    block: BlockStatement;
    handler: CatchClause | null;
    finalizer: BlockStatement | null;
}

The differences are:

• handlers (an array of CatchClause) is changed to handler (a single CatchClause, if any)
• guardedHandlers is gone

See also https://bugzilla.mozilla.org/show_bug.cgi?id=742612.

(Migrated from https://code.google.com/p/esprima/issues/detail?id=433)

[ariya]

Since this a breaking change for Esprima (requiring a major version bump), I will also file an issue for a transition step.

[ariya]

I've updated it so that the empty guardedHandlers should be also removed (ref estree/estree#24).

[ariya]

From our downstream tests, this is going to break (at least) js2cofee and webpack. I plan to propose a change to those projects before changing this.