[Frontend] Add whether allowing compiler errors to the pretty stacktrace

While this will be in the compiler arguments, it's easy to miss when
skimming over the pretty stacktrace. Add an explicit message to make it
easier to see while looking over crashes.

Author: bnbarham

lib/FrontendTool/FrontendTool.cpp

@@ -1813,19 +1813,22 @@ createJSONFixItDiagnosticConsumerIfNeeded(
 
 /// A PrettyStackTraceEntry to print frontend information useful for debugging.
 class PrettyStackTraceFrontend : public llvm::PrettyStackTraceEntry {
-  const LangOptions &LangOpts;
+  const CompilerInvocation &Invocation;
 
 public:
-  PrettyStackTraceFrontend(const LangOptions &langOpts)
-      : LangOpts(langOpts) {}
+  PrettyStackTraceFrontend(const CompilerInvocation &invocation)
+      : Invocation(invocation) {}
 
   void print(llvm::raw_ostream &os) const override {
-    auto effective = LangOpts.EffectiveLanguageVersion;
+    auto effective = Invocation.getLangOptions().EffectiveLanguageVersion;
     if (effective != version::Version::getCurrentLanguageVersion()) {
       os << "Compiling with effective version " << effective;
     } else {
       os << "Compiling with the current language version";
     }
+    if (Invocation.getFrontendOptions().AllowModuleWithCompilerErrors) {
+      os << " while allowing modules with compiler errors";
+    }
     os << "\n";
   };
 };
@@ -1936,7 +1939,7 @@ int swift::performFrontend(ArrayRef<const char *> Args,
   /// (leaks checking is not thread safe).
   Invocation.getSILOptions().checkSILModuleLeaks = true;
 
-  PrettyStackTraceFrontend frontendTrace(Invocation.getLangOptions());
+  PrettyStackTraceFrontend frontendTrace(Invocation);
 
   // Make an array of PrettyStackTrace objects to dump the configuration files
   // we used to parse the arguments. These are RAII objects, so they and the

test/Frontend/crash.swift

@@ -2,7 +2,7 @@
 // RUN: not --crash %target-swift-frontend -typecheck -debug-crash-after-parse -filelist %t.filelist.txt 2>&1 | %FileCheck %s
 
 // Check that we see the contents of the input file list in the crash log.
-// CHECK-NOT: Compiling with {{.*}} while allowing modules with compiler errors enabled
+// CHECK-NOT: while allowing modules with compiler errors
 // CHECK-LABEL: Stack dump
 // CHECK-NEXT: Program arguments: {{.*swift(-frontend)?(c?)(\.exe)?}}
 // CHECK-NEXT: Swift version
@@ -14,12 +14,11 @@
 
 // RUN: not --crash %target-swift-frontend -typecheck -debug-crash-after-parse -experimental-allow-module-with-compiler-errors %s 2>&1 | %FileCheck -check-prefix CHECK-ALLOW %s
 // CHECK-ALLOW: Program arguments: {{.*}} -experimental-allow-module-with-compiler-errors
-// CHECK-ALLOW: Compiling with effective version
+// CHECK-ALLOW: Compiling with effective version {{.*}} while allowing modules with compiler errors
 
 // RUN: not --crash %target-swift-frontend -typecheck -debug-crash-after-parse -experimental-allow-module-with-compiler-errors -swift-version 5 %s 2>&1 | %FileCheck -check-prefix CHECK-CURRENT %s
 // CHECK-CURRENT: Program arguments: {{.*}} -experimental-allow-module-with-compiler-errors
-// CHECK-CURRENT: Compiling with the current language version
+// CHECK-CURRENT: Compiling with the current language version while allowing modules with compiler errors
 
 func anchor() {}
 anchor()
-