[SR-6909] libSyntax doesn't know about operator precedence

[dabrahams]

Previous ID	SR-6909
Radar	None
Original Reporter	@dabrahams
Type	Bug

Additional Detail from JIRA

Votes	0
Component/s	Source Tooling
Labels	Bug, Syntax
Assignee	None
Priority	Medium

md5: 2493838608afee26863c2c17f96fb301

Issue Description:

If you want to line-break an expression, you want to break it near lower-precedence operators, so you end up with

longThing1 * longThing2
+ longThing3 * longThing4

rather than

longThing1 * longThing2 + longThing3
   * longThing4

or worse:

longThing1
    * longThing2 + longThing3
    * longThing4

But libSyntax is flattening all of that into SequenceExprSyntax so that information is lost. I realize that file-at-a-time processing can't always do this reliably, but... it could try. And it could know about the precedences in the standard library.

[AnthonyLatsis]

libSyntax was removed in #62145 and succeeded by swift-syntax.