AST: Replace recently-added IsInOut bit with simpler check, NFC

Thanks to @lattner for the suggestion.

include/swift/AST/Decl.h

@@ -288,11 +288,6 @@ class alignas(1 << DeclAlignInBits) Decl {
     /// once (either in its declaration, or once later), making it immutable.
     unsigned IsLet : 1;
 
-    /// \brief Whether this is an 'inout' parameter; this is preferable
-    /// to checking if the parameter type is an InOutType, because invalid
-    /// inout parameters have an error type.
-    unsigned IsInOut : 1;
-
     /// \brief Whether this vardecl has an initial value bound to it in a way
     /// that isn't represented in the AST with an initializer in the pattern
     /// binding.  This happens in cases like "for i in ...", switch cases, etc.
@@ -306,7 +301,7 @@ class alignas(1 << DeclAlignInBits) Decl {
     /// a.storage for lazy var a is a decl that cannot be accessed.
     unsigned IsUserAccessible : 1;
   };
-  enum { NumVarDeclBits = NumAbstractStorageDeclBits + 6 };
+  enum { NumVarDeclBits = NumAbstractStorageDeclBits + 5 };
   static_assert(NumVarDeclBits <= 32, "fits in an unsigned");
   
   class EnumElementDeclBitfields {
@@ -4250,7 +4245,6 @@ protected:
     VarDeclBits.IsUserAccessible = true;
     VarDeclBits.IsStatic = IsStatic;
     VarDeclBits.IsLet = IsLet;
-    VarDeclBits.IsInOut = false;
     VarDeclBits.IsDebuggerVar = false;
     VarDeclBits.HasNonPatternBindingInit = false;
     setType(Ty);
@@ -4348,10 +4342,6 @@ public:
   bool isLet() const { return VarDeclBits.IsLet; }
   void setLet(bool IsLet) { VarDeclBits.IsLet = IsLet; }
 
-  /// Is this an 'inout' parameter?
-  bool isInOut() const { return VarDeclBits.IsInOut; }
-  void setInOut(bool InOut) { VarDeclBits.IsInOut = InOut; }
-
   /// Return true if this vardecl has an initial value bound to it in a way
   /// that isn't represented in the AST with an initializer in the pattern
   /// binding.  This happens in cases like "for i in ...", switch cases, etc.

lib/Parse/ParsePattern.cpp

@@ -387,10 +387,8 @@ mapParsedParameters(Parser &parser,
     // If a type was provided, create the type for the parameter.
     if (auto type = paramInfo.Type) {
       // If 'inout' was specified, turn the type into an in-out type.
-      if (specifierKind == Parser::ParsedParameter::InOut) {
+      if (specifierKind == Parser::ParsedParameter::InOut)
         type = new (ctx) InOutTypeRepr(type, paramInfo.LetVarInOutLoc);
-        param->setInOut(true);
-      }
 
       param->getTypeLoc() = TypeLoc(type);
     } else if (paramContext != Parser::ParameterContextKind::Closure) {

lib/Sema/TypeCheckDecl.cpp

@@ -1121,7 +1121,6 @@ Type swift::configureImplicitSelf(TypeChecker &tc,
   // 'self' is 'let' for reference types (i.e., classes) or when 'self' is
   // neither inout.
   selfDecl->setLet(!selfTy->is<InOutType>());
-  selfDecl->setInOut(selfTy->is<InOutType>());
   selfDecl->overwriteType(selfTy);
   
   // Install the self type on the Parameter that contains it.  This ensures that

lib/Sema/TypeCheckPattern.cpp

@@ -781,7 +781,7 @@ static bool validateParameterType(ParamDecl *decl, DeclContext *DC,
   // If the param is not a 'let' and it is not an 'inout'.
   // It must be a 'var'. Provide helpful diagnostics like a shadow copy
   // in the function body to fix the 'var' attribute.
-  if (!decl->isLet() && !decl->isInOut()) {
+  if (!decl->isLet() && !Ty->is<InOutType>() && !hadError) {
     auto func = dyn_cast_or_null<AbstractFunctionDecl>(DC);
     diagnoseAndMigrateVarParameterToBody(decl, func, TC);
     decl->setInvalid();
@@ -829,7 +829,6 @@ bool TypeChecker::typeCheckParameterList(ParameterList *PL, DeclContext *DC,
     
     checkTypeModifyingDeclAttributes(param);
     if (param->getType()->is<InOutType>()) {
-      param->setInOut(true);
       param->setLet(false);
     }
   }
@@ -1101,7 +1100,6 @@ bool TypeChecker::coercePatternToType(Pattern *&P, DeclContext *dc, Type type,
 
     checkTypeModifyingDeclAttributes(var);
     if (type->is<InOutType>()) {
-      NP->getDecl()->setInOut(true);
       NP->getDecl()->setLet(false);
     }
     if (var->getAttrs().hasAttribute<OwnershipAttr>())
@@ -1563,7 +1561,6 @@ bool TypeChecker::coerceParameterListToType(ParameterList *P, DeclContext *DC,
 
     if (!ty->isMaterializable()) {
       if (ty->is<InOutType>()) {
-        param->setInOut(true);
         param->setLet(false);
       } else if (param->hasName()) {
         diagnose(param->getStartLoc(),

validation-test/IDE/crashers/069-swift-typechecker-typecheckparameterlist.swift

@@ -1,3 +0,0 @@
-// RUN: not --crash %target-swift-ide-test -code-completion -code-completion-token=A -source-filename=%s
-// REQUIRES: asserts
-func b(e:({#^A^#var e){

validation-test/IDE/crashers_fixed/069-swift-typechecker-typecheckparameterlist.swift

@@ -0,0 +1,3 @@
+// RUN: %target-swift-ide-test -code-completion -code-completion-token=A -source-filename=%s
+// REQUIRES: asserts
+func b(e:({#^A^#var e){