Shared style variables

Variable scope (08.6)

Shared paint,filter and query expressions support let/var. Variables are visible in the let result; inner bindings shadow outer ones. Binding values resolve only enclosing-scope variables. Bindings evaluate on demand,so unused runtime errors do not execute. Names use nonempty ASCII letters/digits/underscores,up to256 bytes. Unbound names and invalid structures reject before mutation.

map.setPaintProperty('places-layer','circle-color',
  ['let','selected',['boolean',['feature-state','selected'],false],
   ['case',['var','selected'],'#ff00ff','#0000ff']]);
map.setPaintProperty('places-layer','circle-radius',
  ['let','large',18,['step',['zoom'],6,4,['var','large']]]);
await map.sqs.flush({render:true});

Camera zoom may drive a terminal step/interpolate inside outer let expressions; it cannot appear in binding values or other positions. Shared layers continue reevaluating actual zoom. Each evaluation permits8192 steps/64 levels; AST limits remain1024 nodes/32 levels. Budget failures use existing paint defaults/warnings; layer/query filters report RESOURCE_LIMIT and mutations leave no partial layer/reference.

The complete HTML and portable script include all buttons,credits and cleanup through native and real WASM main-thread/strict Worker. Implementation is independent against the public expression specification,without MapLibre code. Remaining operators and complete layer types continue in tasks.