[SILProfiler] Don't crash when coverage info for lazy getters is inco…

lib/SIL/SILProfiler.cpp

@@ -260,6 +260,16 @@ struct MapRegionCounters : public ASTWalker {
     } else if (auto *ACE = dyn_cast<AbstractClosureExpr>(E)) {
       return visitClosureExpr(*this, ACE, [&] { mapRegion(ACE); });
     }
+
+    // rdar://42792053
+    // TODO: There's an outstanding issue here with LazyInitializerExpr. A LIE
+    // is copied into the body of a property getter after type-checking (before
+    // coverage). ASTWalker only visits this expression once via the property's
+    // VarDecl, and does not visit it again within the getter. This results in
+    // missing coverage. SILGen treats the init expr as part of the getter, but
+    // its SILProfiler has no information about the init because the LIE isn't
+    // visited here.
+
     return {true, E};
   }
 };

lib/SILGen/SILGenFunction.cpp

@@ -653,8 +653,10 @@ void SILGenFunction::emitProfilerIncrement(ASTNode N) {
   auto &C = B.getASTContext();
   const auto &RegionCounterMap = SP->getRegionCounterMap();
   auto CounterIt = RegionCounterMap.find(N);
-  assert(CounterIt != RegionCounterMap.end() &&
-         "cannot increment non-existent counter");
+
+  // TODO: Assert that this cannot happen (rdar://42792053).
+  if (CounterIt == RegionCounterMap.end())
+    return;
 
   auto Int32Ty = getLoweredType(BuiltinIntegerType::get(32, C));
   auto Int64Ty = getLoweredType(BuiltinIntegerType::get(64, C));

test/Profiler/coverage_class.swift

@@ -39,3 +39,11 @@ struct S2 {
   // CHECK-NEXT: [[@LINE+1]]:26 -> [[@LINE+1]]:27 : (1 - 0)
   var m1: Int = g1 ? 0 : 1
 }
+
+// Test that the crash from SR-8429 is avoided. Follow-up work is
+// needed to generate the correct coverage mapping here. Coverage for
+// `offset` should be associated with its getter, not the class
+// constructor.
+class C2 {
+  lazy var offset: Int = true ? 30 : 55
+}