[Coverage] Make ~ProfilerRAII restore the correct context

Swift permits function decls within function decls. ~ProfilerRAII would
destroy the current profiling context upon entering a nested function
decl instead of preserving it for later use. Fix the issue by recording
the correct context in ProfilerRAII.

Author: vedantk

lib/SILGen/SILGenProfiling.cpp

@@ -30,13 +30,14 @@ using namespace swift;
 using namespace Lowering;
 
 static bool isUnmappedDecl(Decl *D) {
-  return (D->isImplicit() && !isa<ConstructorDecl>(D) &&
-          !isa<DestructorDecl>(D)) ||
-         isa<EnumCaseDecl>(D);
+  if (isa<ConstructorDecl>(D) || isa<DestructorDecl>(D))
+    return false;
+
+  return D->isImplicit() || isa<EnumCaseDecl>(D);
 }
 
 ProfilerRAII::ProfilerRAII(SILGenModule &SGM, AbstractFunctionDecl *D)
-    : SGM(SGM) {
+    : SGM(SGM), PreviousProfiler(std::move(SGM.Profiler)) {
   const auto &Opts = SGM.M.getOptions();
   if (!Opts.GenerateProfile || isUnmappedDecl(D))
     return;
@@ -45,7 +46,7 @@ ProfilerRAII::ProfilerRAII(SILGenModule &SGM, AbstractFunctionDecl *D)
   SGM.Profiler->assignRegionCounters(D);
 }
 
-ProfilerRAII::~ProfilerRAII() { SGM.Profiler = nullptr; }
+ProfilerRAII::~ProfilerRAII() { SGM.Profiler = std::move(PreviousProfiler); }
 
 namespace {
 

lib/SILGen/SILGenProfiling.h

@@ -27,12 +27,7 @@ namespace Lowering {
 class SILGenModule;
 class SILGenBuilder;
 
-/// RAII object to set up profiling for a function.
-struct ProfilerRAII {
-  SILGenModule &SGM;
-  ProfilerRAII(SILGenModule &SGM, AbstractFunctionDecl *D);
-  ~ProfilerRAII();
-};
+struct ProfilerRAII;
 
 /// Profiling state.
 class SILGenProfiling {
@@ -67,6 +62,15 @@ class SILGenProfiling {
   friend struct ProfilerRAII;
 };
 
+/// RAII object to set up profiling for a function.
+struct ProfilerRAII {
+  SILGenModule &SGM;
+  std::unique_ptr<SILGenProfiling> PreviousProfiler;
+
+  ProfilerRAII(SILGenModule &SGM, AbstractFunctionDecl *D);
+  ~ProfilerRAII();
+};
+
 } // end namespace Lowering
 } // end namespace swift
 

test/SILGen/coverage_smoke.swift

@@ -53,4 +53,15 @@ func main() {
   let _ = Class1()
 }
 
+// rdar://problem/22761498 - enum declaration suppresses coverage
+func foo() {
+  var x : Int32 = 0   // CHECK-COV: 1|{{.*}}[[@LINE]]
+  enum ETy { case A } // CHECK-COV: 1|{{.*}}[[@LINE]]
+  repeat {            // CHECK-COV: 1|{{.*}}[[@LINE]]
+    x += 1            // CHECK-COV: 1|{{.*}}[[@LINE]]
+  } while x == 0      // CHECK-COV: 1|{{.*}}[[@LINE]]
+  x += 1              // CHECK-COV: 1|{{.*}}[[@LINE]]
+}
+
 main()
+foo()