Revert "Add -async-main flag to favor asynchronous main"

This reverts commit da0a331.

Author: etcwilde

include/swift/Basic/LangOptions.h

@@ -223,9 +223,6 @@ namespace swift {
     /// Emit a remark after loading a module.
     bool EnableModuleLoadingRemarks = false;
 
-    /// Resolve main function as though it were called from an async context
-    bool EnableAsyncMainResolution = false;
-
     ///
     /// Support for alternate usage modes
     ///

include/swift/Option/Options.td

@@ -270,10 +270,6 @@ def pch_output_dir: Separate<["-"], "pch-output-dir">,
   Flags<[FrontendOption, HelpHidden, ArgumentIsPath]>,
   HelpText<"Directory to persist automatically created precompiled bridging headers">;
 
-def async_main: Flag<["-"], "async-main">,
-    Flags<[FrontendOption]>,
-    HelpText<"Resolve main function as if it were called from an asynchronous context">;
-
 // FIXME: Unhide this once it doesn't depend on an output file map.
 def incremental : Flag<["-"], "incremental">,
   Flags<[NoInteractiveOption, HelpHidden, DoesNotAffectIncrementalBuild]>,

include/swift/Sema/ConstraintSystem.h

@@ -1535,7 +1535,7 @@ enum class ConstraintSystemFlags {
   /// Note that this flag is automatically applied to all constraint systems,
   /// when \c DebugConstraintSolver is set in \c TypeCheckerOptions. It can be
   /// automatically enabled for select constraint solving attempts by setting
-  /// \c DebugConstraintSolverAttempt. Finally, it can also be automatically 
+  /// \c DebugConstraintSolverAttempt. Finally, it can also be automatically
   /// enabled for a pre-configured set of expressions on line numbers by setting
   /// \c DebugConstraintSolverOnLines.
   DebugConstraints = 0x10,
@@ -1559,10 +1559,6 @@ enum class ConstraintSystemFlags {
   /// calling conventions, say due to Clang attributes such as
   /// `__attribute__((ns_consumed))`.
   UseClangFunctionTypes = 0x80,
-
-  /// When set, nominal typedecl contexts are asynchronous contexts.
-  /// This is set while searching for the main function
-  ConsiderNominalTypeContextsAsync = 0x100,
 };
 
 /// Options that affect the constraint system as a whole.

include/swift/Sema/IDETypeChecking.h

@@ -21,7 +21,6 @@
 
 #include "swift/AST/Identifier.h"
 #include "swift/Basic/SourceLoc.h"
-#include "swift/Basic/OptionSet.h"
 #include <memory>
 #include <tuple>
 
@@ -51,8 +50,6 @@ namespace swift {
   class ConstraintSystem;
   class Solution;
   class SolutionApplicationTarget;
-  enum class ConstraintSystemFlags;
-  using ConstraintSystemOptions = OptionSet<ConstraintSystemFlags>;
   }
 
   /// Typecheck binding initializer at \p bindingIndex.
@@ -96,9 +93,8 @@ namespace swift {
   /// Unlike other member lookup functions, \c swift::resolveValueMember()
   /// should be used when you want to look up declarations with the same name as
   /// one you already have.
-  ResolvedMemberResult
-  resolveValueMember(DeclContext &DC, Type BaseTy, DeclName Name,
-                     constraints::ConstraintSystemOptions Options = {});
+  ResolvedMemberResult resolveValueMember(DeclContext &DC, Type BaseTy,
+                                          DeclName Name);
 
   /// Given a type and an extension to the original type decl of that type,
   /// decide if the extension has been applied, i.e. if the requirements of the

lib/Driver/ToolChains.cpp

@@ -300,7 +300,6 @@ void ToolChain::addCommonFrontendArgs(const OutputInfo &OI,
   inputArgs.AddLastArg(arguments, options::OPT_access_notes_path);
   inputArgs.AddLastArg(arguments, options::OPT_library_level);
   inputArgs.AddLastArg(arguments, options::OPT_enable_bare_slash_regex);
-  inputArgs.AddLastArg(arguments, options::OPT_async_main);
 
   // Pass on any build config options
   inputArgs.AddAllArgs(arguments, options::OPT_D);

lib/Frontend/CompilerInvocation.cpp

@@ -497,8 +497,6 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     Diags.diagnose(SourceLoc(), diag::warn_flag_deprecated,
                    "-enable-experimental-async-top-level");
 
-  Opts.EnableAsyncMainResolution = Args.hasArg(OPT_async_main);
-
   Opts.DiagnoseInvalidEphemeralnessAsError |=
       Args.hasArg(OPT_enable_invalid_ephemeralness_as_error);
 

lib/Sema/CSGen.cpp

@@ -4417,11 +4417,10 @@ getMemberDecls(InterestedMemberKind Kind) {
   llvm_unreachable("unhandled kind");
 }
 
-ResolvedMemberResult
-swift::resolveValueMember(DeclContext &DC, Type BaseTy, DeclName Name,
-                          ConstraintSystemOptions Options) {
+ResolvedMemberResult swift::resolveValueMember(DeclContext &DC, Type BaseTy,
+                                               DeclName Name) {
   ResolvedMemberResult Result;
-  ConstraintSystem CS(&DC, Options);
+  ConstraintSystem CS(&DC, None);
 
   // Look up all members of BaseTy with the given Name.
   MemberLookupResult LookupResult = CS.performMemberLookup(

lib/Sema/ConstraintSystem.cpp

@@ -2900,11 +2900,6 @@ bool ConstraintSystem::isAsynchronousContext(DeclContext *dc) {
         FunctionType::ExtInfo()).isAsync();
   }
 
-  if (Options.contains(
-          ConstraintSystemFlags::ConsiderNominalTypeContextsAsync) &&
-      isa<NominalTypeDecl>(dc))
-    return true;
-
   return false;
 }
 

lib/Sema/TypeCheckAttr.cpp

@@ -2171,14 +2171,8 @@ SynthesizeMainFunctionRequest::evaluate(Evaluator &evaluator,
   // mainType.main() from the entry point, and that would require fully
   // type-checking the call to mainType.main().
 
-  constraints::ConstraintSystemOptions lookupOptions;
-  if (context.LangOpts.EnableAsyncMainResolution)
-    lookupOptions |=
-        constraints::ConstraintSystemFlags::ConsiderNominalTypeContextsAsync;
-
   auto resolution = resolveValueMember(
-      *declContext, nominal->getInterfaceType(), context.Id_main,
-      lookupOptions);
+      *declContext, nominal->getInterfaceType(), context.Id_main);
   FuncDecl *mainFunction =
       resolveMainFunctionDecl(declContext, resolution, context);
   if (!mainFunction) {