NFC: SimpleRequest::diagnoseCycle will debug dump in asserts

Author: kavon

include/swift/AST/SimpleRequest.h

@@ -318,6 +318,7 @@ class SimpleRequest<Derived, Output(Inputs...), Caching> {
   }
 
   void diagnoseCycle(DiagnosticEngine &diags) const {
+    debugDumpCycles = CONDITIONAL_ASSERT_enabled();
     diags.diagnose(asDerived().getNearestLoc(), diag::circular_reference);
   }
 

lib/AST/Evaluator.cpp

@@ -90,39 +90,45 @@ void Evaluator::finishedRequest(const ActiveRequest &request) {
 }
 
 void Evaluator::diagnoseCycle(const ActiveRequest &request) {
-  if (debugDumpCycles) {
-    const auto printIndent = [](llvm::raw_ostream &OS, unsigned indent) {
-      OS.indent(indent);
-      OS << "`--";
-    };
-
-    unsigned indent = 1;
-    auto &OS = llvm::errs();
-
-    OS << "===CYCLE DETECTED===\n";
-    for (const auto &step : activeRequests) {
-      printIndent(OS, indent);
-      if (step == request) {
-        OS.changeColor(llvm::raw_ostream::GREEN);
-        simple_display(OS, step);
-        OS.resetColor();
-      } else {
-        simple_display(OS, step);
+  auto dumpCycles = [&]() {
+    if (debugDumpCycles) {
+      const auto printIndent = [](llvm::raw_ostream &OS, unsigned indent) {
+        OS.indent(indent);
+        OS << "`--";
+      };
+
+      unsigned indent = 1;
+      auto &OS = llvm::errs();
+
+      OS << "===CYCLE DETECTED===\n";
+      for (const auto &step : activeRequests) {
+        printIndent(OS, indent);
+        if (step == request) {
+          OS.changeColor(llvm::raw_ostream::GREEN);
+          simple_display(OS, step);
+          OS.resetColor();
+        } else {
+          simple_display(OS, step);
+        }
+        OS << "\n";
+        indent += 4;
       }
-      OS << "\n";
-      indent += 4;
-    }
 
-    printIndent(OS, indent);
-    OS.changeColor(llvm::raw_ostream::GREEN);
-    simple_display(OS, request);
+      printIndent(OS, indent);
+      OS.changeColor(llvm::raw_ostream::GREEN);
+      simple_display(OS, request);
 
-    OS.changeColor(llvm::raw_ostream::RED);
-    OS << " (cyclic dependency)";
-    OS.resetColor();
+      OS.changeColor(llvm::raw_ostream::RED);
+      OS << " (cyclic dependency)";
+      OS.resetColor();
 
-    OS << "\n";
-  }
+      OS << "\n";
+    }
+  };
+  
+  // -debug-cycles is deferred to allow SimpleRequest to enable dumping if
+  // the request has not overridden diagnoseCycle.
+  SWIFT_DEFER { dumpCycles(); }
 
   // Perform some filtering to avoid emitting duplicate 'through reference here'
   // notes.