Add LifetimeDependenceDiagnoseTrivial feature.

A feature flag is needed so that newer compilers can build older standard
library interfaces.

Author: atrick

include/swift/Basic/Features.def

@@ -358,6 +358,9 @@ EXPERIMENTAL_FEATURE(StructLetDestructuring, true)
 /// Enable returning non-escapable types from functions.
 EXPERIMENTAL_FEATURE(LifetimeDependence, true)
 
+/// Enable LifetimeDependence diagnostics for trivial types.
+EXPERIMENTAL_FEATURE(LifetimeDependenceDiagnoseTrivial, false)
+
 /// Enable the `@_staticExclusiveOnly` attribute.
 EXPERIMENTAL_FEATURE(StaticExclusiveOnly, true)
 

lib/AST/FeatureSet.cpp

@@ -262,6 +262,8 @@ static bool usesFeatureLifetimeDependence(Decl *decl) {
       ->hasLifetimeDependencies();
 }
 
+UNINTERESTING_FEATURE(LifetimeDependenceDiagnoseTrivial)
+
 UNINTERESTING_FEATURE(DynamicActorIsolation)
 UNINTERESTING_FEATURE(NonfrozenEnumExhaustivity)
 UNINTERESTING_FEATURE(ClosureIsolation)