usageLogEnabled property
Opt-in instrumentation toggle. When true, extractBridgedArg and the
interpreter's generic-constructor path record each relaxer /
interface-proxy / type-coercion / generic-constructor hit and each
unresolved miss, keyed by category + base type + type-argument. The
accumulated data drives the mass-generation reduction work (P&R steps
4–5): it reveals which generated cases real scripts actually exercise.
Defaults to false. Every instrumentation call site guards on this flag
before composing any log key, so the log is completely silent and
zero-overhead when disabled.
Web note: this flag is purely programmatic here (no dart:io). The VM
D4rt facade additionally defaults it from the D4RT_LOG_RELAXER_USAGE
environment variable; the web-capable tom_d4rt_ast twin cannot read
environment variables, so callers enable it directly. This is the only
deliberate twin divergence for this feature.
Implementation
static bool usageLogEnabled = false;