Serialization: Intro enableExtendedDeserializationRecovery

Introduce a new deserialization mode `enableExtendedDeserializationRecovery`
for use when we can afford inconsistent information from a swiftmodule
file. It's enabled automatically in debugger mode, when user errors are
allowed and during index-while-building.

Author: xymus

include/swift/AST/ASTContext.h

@@ -381,11 +381,10 @@ class ASTContext final {
   /// files?
   bool IgnoreAdjacentModules = false;
 
-  /// Override to accept reading errors from swiftmodules and being generally
-  /// more tolerant to inconsistencies. This is enabled for
-  /// index-while-building as it runs last and it can afford to read an AST
-  /// with inconsistencies.
-  bool ForceAllowModuleWithCompilerErrors = false;
+  /// Accept recovering from more issues at deserialization, even if it can
+  /// lead to an inconsistent state. This is enabled for index-while-building
+  /// as it runs last and it can afford to read an AST with inconsistencies.
+  bool ForceExtendedDeserializationRecovery = false;
 
   // Define the set of known identifiers.
 #define IDENTIFIER_WITH_NAME(Name, IdStr) Identifier Id_##Name;

lib/Index/Index.cpp

@@ -2168,7 +2168,7 @@ void index::indexModule(ModuleDecl *module, IndexDataConsumer &consumer) {
     return;
   }
 
-  llvm::SaveAndRestore<bool> S(ctx.ForceAllowModuleWithCompilerErrors, true);
+  llvm::SaveAndRestore<bool> S(ctx.ForceExtendedDeserializationRecovery, true);
 
   IndexSwiftASTWalker walker(consumer, ctx);
   walker.visitModule(*module);

lib/Serialization/ModuleFile.cpp

@@ -135,8 +135,15 @@ ModuleFile::ModuleFile(std::shared_ptr<const ModuleFileSharedCore> core)
 }
 
 bool ModuleFile::allowCompilerErrors() const {
-  return getContext().LangOpts.AllowModuleWithCompilerErrors ||
-         getContext().ForceAllowModuleWithCompilerErrors;
+  return getContext().LangOpts.AllowModuleWithCompilerErrors;
+}
+
+bool ModuleFile::enableExtendedDeserializationRecovery() const {
+  ASTContext &ctx = getContext();
+  return ctx.LangOpts.EnableDeserializationRecovery &&
+         (allowCompilerErrors() ||
+          ctx.LangOpts.DebuggerSupport ||
+          ctx.ForceExtendedDeserializationRecovery);
 }
 
 Status

lib/Serialization/ModuleFile.h

@@ -691,6 +691,10 @@ class ModuleFile
   /// '-experimental-allow-module-with-compiler-errors' is currently enabled).
   bool allowCompilerErrors() const;
 
+  /// Allow recovering from errors that could be unsafe when compiling
+  /// the binary. Useful for the debugger and IDE support tools.
+  bool enableExtendedDeserializationRecovery() const;
+
   /// \c true if this module has incremental dependency information.
   bool hasIncrementalInfo() const { return Core->hasIncrementalInfo(); }