jsAssignmentExpr not working

[larsbs]

syntax match   jsAssignmentExpr     /\v%([a-zA-Z_$]\k*\.)*[a-zA-Z_$]\k*\s*\=\(>\)\@!/ contains=jsFuncAssignExpr,jsAssignExpIdent,jsPrototype,jsOperator,jsThis,jsNoise,jsArgsObj
syntax match   jsAssignExpIdent     /\v[a-zA-Z_$]\k*\ze%(\s*\=)/ contained
syntax match   jsFuncAssignExpr     /\v%(%([a-zA-Z_$]\k*\.)*[a-zA-Z_$]\k*\s*\=\s*){-1,}\ze%(function\s*\*?\s*\()/ contains=jsFuncAssignObjChain,jsFuncAssignIdent,jsFunction,jsPrototype,jsOperator,jsThis,jsArgsObj contained
syntax match   jsFuncAssignObjChain /\v%([a-zA-Z_$]\k*\.)+/ contains=jsPrototype,jsNoise contained
syntax match   jsFuncAssignIdent    /\v[a-zA-Z_$]\k*\ze%(\s*\=)/ contained

This doesn't match anything by now and I've seen in previous pull request that this used to work. I'm using https://github.com/gerw/vim-HiLinkTrace to check it.

Look in the bottom bar that HiLinkTrace doesn't show anything when the cursor is positioned in the name of the function.

[larsbs]

The offending part of the regex is at the end of jsAssignmentExpr. If \(>\)\@! is removed, everything work like a charm. What's the purpose of those bits?

[larsbs]

This is the commit where the last part of the regex was included: 325c048

[wchargin]

The offending characters should read %(\>)@!, and I think just \>@! should work fine as well.

In normal vim regexes, \(>\)\@! means "match the group containing the character >, then perform a negative-lookahead," which ends up meaning "fail the match if the next character is >." In this case, the author wanted to match x = 3 but not x => 3.

However, this regex has \v at the start, which stands for "very magic" (:help \v), so the groups and lookahead don't need to have a backslash, and the > character does.

The %() group, as opposed to (), is better because it's non-capturing, so it's faster and can be used in some places that forbid capturing (I forget whether syntax is one of these). But @! matches the previous atom, and > is a single-character atom by itself, so the group is unnecessary.

Test document:

let myVar = 87;
let myFunc = x => 3;
// vim: hlsearch

Exactly myVar and myFunc should be highlighted.

[davidchambers]

Thanks for the explanation, @wchargin!