[analyzer] EnumCastOutOfRangeChecker: report the value (llvm#74503)

...that is causing the bug report when it's converted to the enum type.
This commit only improves the diagnostics and does not affect the set of
reports.

clang/lib/StaticAnalyzer/Checkers/EnumCastOutOfRangeChecker.cpp

@@ -22,10 +22,12 @@
 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+#include "llvm/Support/FormatVariadic.h"
 #include <optional>
 
 using namespace clang;
 using namespace ento;
+using llvm::formatv;
 
 namespace {
 // This evaluator checks two SVals for equality. The first SVal is provided via
@@ -87,17 +89,22 @@ void EnumCastOutOfRangeChecker::reportWarning(CheckerContext &C,
       EnumValueCastOutOfRange.reset(
           new BugType(this, "Enum cast out of range"));
 
-    llvm::SmallString<128> Msg{"The value provided to the cast expression is "
-                               "not in the valid range of values for "};
-    StringRef EnumName{E->getName()};
-    if (EnumName.empty()) {
-      Msg += "the enum";
-    } else {
-      Msg += '\'';
-      Msg += EnumName;
-      Msg += '\'';
+    std::string ValueStr = "", NameStr = "the enum";
+
+    // Try to add details to the message:
+    const auto ConcreteValue =
+        C.getSVal(CE->getSubExpr()).getAs<nonloc::ConcreteInt>();
+    if (ConcreteValue) {
+      ValueStr = formatv(" '{0}'", ConcreteValue->getValue());
+    }
+    if (StringRef EnumName{E->getName()}; !EnumName.empty()) {
+      NameStr = formatv("'{0}'", EnumName);
     }
 
+    std::string Msg = formatv("The value{0} provided to the cast expression is "
+                              "not in the valid range of values for {1}",
+                              ValueStr, NameStr);
+
     auto BR = std::make_unique<PathSensitiveBugReport>(*EnumValueCastOutOfRange,
                                                        Msg, N);
     bugreporter::trackExpressionValue(N, CE->getSubExpr(), *BR);