[NFC, Scoped Enum] Convert Sema::ExpressionEvaluationContext into a scoped Enum

- also replace direct equality checks against the ConstantEvaluated enumerator  with isConstantEvaluted(), in anticipation of adding finer granularity to the various ConstantEvaluated contexts and reinstating certain restrictions on where lambda expressions can occur in C++17.

- update the clang tablegen backend that uses these Enumerators, and add the relevant scope where needed.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@299316 91177308-0d34-0410-b5e6-96231b3b80d8

Author: faisalv

include/clang/Sema/Sema.h

@@ -681,7 +681,8 @@ class Sema {
       : S(S), SavedContext(S, DC)
     {
       S.PushFunctionScope();
-      S.PushExpressionEvaluationContext(Sema::PotentiallyEvaluated);
+      S.PushExpressionEvaluationContext(
+          Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
     }
 
     ~SynthesizedFunctionScope() {
@@ -802,7 +803,7 @@ class Sema {
 
   /// \brief Describes how the expressions currently being parsed are
   /// evaluated at run-time, if at all.
-  enum ExpressionEvaluationContext {
+  enum class ExpressionEvaluationContext {
     /// \brief The current expression and its subexpressions occur within an
     /// unevaluated operand (C++11 [expr]p7), such as the subexpression of
     /// \c sizeof, where the type of the expression may be significant but
@@ -908,8 +909,12 @@ class Sema {
     MangleNumberingContext &getMangleNumberingContext(ASTContext &Ctx);
 
     bool isUnevaluated() const {
-      return Context == Unevaluated || Context == UnevaluatedAbstract ||
-             Context == UnevaluatedList;
+      return Context == ExpressionEvaluationContext::Unevaluated ||
+             Context == ExpressionEvaluationContext::UnevaluatedAbstract ||
+             Context == ExpressionEvaluationContext::UnevaluatedList;
+    }
+    bool isConstantEvaluated() const {
+      return Context == ExpressionEvaluationContext::ConstantEvaluated;
     }
   };
 
@@ -10315,6 +10320,7 @@ class EnterExpressionEvaluationContext {
   bool Entered = true;
 
 public:
+
   EnterExpressionEvaluationContext(Sema &Actions,
                                    Sema::ExpressionEvaluationContext NewContext,
                                    Decl *LambdaContextDecl = nullptr,
@@ -10345,8 +10351,8 @@ class EnterExpressionEvaluationContext {
     // a context.
     if (ShouldEnter && Actions.isUnevaluatedContext() &&
         Actions.getLangOpts().CPlusPlus11) {
-      Actions.PushExpressionEvaluationContext(Sema::UnevaluatedList, nullptr,
-                                              false);
+      Actions.PushExpressionEvaluationContext(
+          Sema::ExpressionEvaluationContext::UnevaluatedList, nullptr, false);
       Entered = true;
     }
   }

lib/Parse/ParseCXXInlineMethods.cpp

@@ -344,9 +344,9 @@ void Parser::ParseLexedMethodDeclaration(LateParsedMethodDeclaration &LM) {
 
       // The argument isn't actually potentially evaluated unless it is
       // used.
-      EnterExpressionEvaluationContext Eval(Actions,
-                                            Sema::PotentiallyEvaluatedIfUsed,
-                                            Param);
+      EnterExpressionEvaluationContext Eval(
+          Actions,
+          Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed, Param);
 
       ExprResult DefArgResult;
       if (getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace)) {

lib/Parse/ParseDecl.cpp

@@ -308,7 +308,9 @@ unsigned Parser::ParseAttributeArgsCommon(
     do {
       bool Uneval = attributeParsedArgsUnevaluated(*AttrName);
       EnterExpressionEvaluationContext Unevaluated(
-          Actions, Uneval ? Sema::Unevaluated : Sema::ConstantEvaluated,
+          Actions,
+          Uneval ? Sema::ExpressionEvaluationContext::Unevaluated
+                 : Sema::ExpressionEvaluationContext::ConstantEvaluated,
           /*LambdaContextDecl=*/nullptr,
           /*IsDecltype=*/false);
 
@@ -4093,8 +4095,8 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
       // anything that's a simple-type-specifier followed by '(' as an
       // expression. This suffices because function types are not valid
       // underlying types anyway.
-      EnterExpressionEvaluationContext Unevaluated(Actions,
-                                                   Sema::ConstantEvaluated);
+      EnterExpressionEvaluationContext Unevaluated(
+          Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
       TPResult TPR = isExpressionOrTypeSpecifierSimple(NextToken().getKind());
       // If the next token starts an expression, we know we're parsing a
       // bit-field. This is the common case.
@@ -6270,9 +6272,10 @@ void Parser::ParseParameterDeclarationClause(
 
           // The argument isn't actually potentially evaluated unless it is
           // used.
-          EnterExpressionEvaluationContext Eval(Actions,
-                                              Sema::PotentiallyEvaluatedIfUsed,
-                                                Param);
+          EnterExpressionEvaluationContext Eval(
+              Actions,
+              Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed,
+              Param);
 
           ExprResult DefArgResult;
           if (getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace)) {
@@ -6422,8 +6425,8 @@ void Parser::ParseBracketDeclarator(Declarator &D) {
     if (getLangOpts().CPlusPlus) {
       NumElements = ParseConstantExpression();
     } else {
-      EnterExpressionEvaluationContext Unevaluated(Actions,
-                                                   Sema::ConstantEvaluated);
+      EnterExpressionEvaluationContext Unevaluated(
+          Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
       NumElements =
           Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression());
     }
@@ -6558,8 +6561,9 @@ void Parser::ParseTypeofSpecifier(DeclSpec &DS) {
 
   const bool hasParens = Tok.is(tok::l_paren);
 
-  EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated,
-                                               Sema::ReuseLambdaContextDecl);
+  EnterExpressionEvaluationContext Unevaluated(
+      Actions, Sema::ExpressionEvaluationContext::Unevaluated,
+      Sema::ReuseLambdaContextDecl);
 
   bool isCastExpr;
   ParsedType CastTy;

lib/Parse/ParseDeclCXX.cpp

@@ -935,8 +935,9 @@ SourceLocation Parser::ParseDecltypeSpecifier(DeclSpec &DS) {
 
       // C++11 [dcl.type.simple]p4:
       //   The operand of the decltype specifier is an unevaluated operand.
-      EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated,
-                                                   nullptr,/*IsDecltype=*/true);
+      EnterExpressionEvaluationContext Unevaluated(
+          Actions, Sema::ExpressionEvaluationContext::Unevaluated, nullptr,
+          /*IsDecltype=*/true);
       Result =
           Actions.CorrectDelayedTyposInExpr(ParseExpression(), [](Expr *E) {
             return E->hasPlaceholderType() ? ExprError() : E;
@@ -2897,9 +2898,8 @@ ExprResult Parser::ParseCXXMemberInitializer(Decl *D, bool IsFunction,
   assert(Tok.isOneOf(tok::equal, tok::l_brace)
          && "Data member initializer not starting with '=' or '{'");
 
-  EnterExpressionEvaluationContext Context(Actions, 
-                                           Sema::PotentiallyEvaluated,
-                                           D);
+  EnterExpressionEvaluationContext Context(
+      Actions, Sema::ExpressionEvaluationContext::PotentiallyEvaluated, D);
   if (TryConsumeToken(tok::equal, EqualLoc)) {
     if (Tok.is(tok::kw_delete)) {
       // In principle, an initializer of '= delete p;' is legal, but it will

lib/Parse/ParseExpr.cpp

@@ -198,8 +198,8 @@ ExprResult Parser::ParseConstantExpression(TypeCastState isTypeCast) {
   //   An expression is potentially evaluated unless it appears where an
   //   integral constant expression is required (see 5.19) [...].
   // C++98 and C++11 have no such rule, but this is only a defect in C++98.
-  EnterExpressionEvaluationContext ConstantEvaluated(Actions,
-                                               Sema::ConstantEvaluated);
+  EnterExpressionEvaluationContext ConstantEvaluated(
+      Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
 
   ExprResult LHS(ParseCastExpression(false, false, isTypeCast));
   ExprResult Res(ParseRHSOfBinaryExpression(LHS, prec::Conditional));
@@ -1313,7 +1313,8 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
     // C++11 [expr.unary.noexcept]p1:
     //   The noexcept operator determines whether the evaluation of its operand,
     //   which is an unevaluated operand, can throw an exception.
-    EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
+    EnterExpressionEvaluationContext Unevaluated(
+        Actions, Sema::ExpressionEvaluationContext::Unevaluated);
     ExprResult Result = ParseExpression();
 
     T.consumeClose();
@@ -1882,9 +1883,10 @@ ExprResult Parser::ParseUnaryExprOrTypeTraitExpression() {
 
     if (!Name)
       return ExprError();
-    
-    EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated,
-                                                 Sema::ReuseLambdaContextDecl);
+
+    EnterExpressionEvaluationContext Unevaluated(
+        Actions, Sema::ExpressionEvaluationContext::Unevaluated,
+        Sema::ReuseLambdaContextDecl);
 
     return Actions.ActOnSizeofParameterPackExpr(getCurScope(),
                                                 OpTok.getLocation(), 
@@ -1895,8 +1897,9 @@ ExprResult Parser::ParseUnaryExprOrTypeTraitExpression() {
   if (OpTok.isOneOf(tok::kw_alignof, tok::kw__Alignof))
     Diag(OpTok, diag::warn_cxx98_compat_alignof);
 
-  EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated,
-                                               Sema::ReuseLambdaContextDecl);
+  EnterExpressionEvaluationContext Unevaluated(
+      Actions, Sema::ExpressionEvaluationContext::Unevaluated,
+      Sema::ReuseLambdaContextDecl);
 
   bool isCastExpr;
   ParsedType CastTy;
@@ -2569,7 +2572,8 @@ ExprResult Parser::ParseGenericSelectionExpression() {
   {
     // C11 6.5.1.1p3 "The controlling expression of a generic selection is
     // not evaluated."
-    EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
+    EnterExpressionEvaluationContext Unevaluated(
+        Actions, Sema::ExpressionEvaluationContext::Unevaluated);
     ControllingExpr =
         Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression());
     if (ControllingExpr.isInvalid()) {

lib/Parse/ParseExprCXX.cpp

@@ -866,8 +866,8 @@ Optional<unsigned> Parser::ParseLambdaIntroducer(LambdaIntroducer &Intro,
         // Each lambda init-capture forms its own full expression, which clears
         // Actions.MaybeODRUseExprs. So create an expression evaluation context
         // to save the necessary state, and restore it later.
-        EnterExpressionEvaluationContext EC(Actions,
-                                            Sema::PotentiallyEvaluated);
+        EnterExpressionEvaluationContext EC(
+            Actions, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
 
         if (TryConsumeToken(tok::equal))
           InitKind = LambdaCaptureInitKind::CopyInit;
@@ -1405,8 +1405,9 @@ ExprResult Parser::ParseCXXTypeid() {
   // We enter the unevaluated context before trying to determine whether we
   // have a type-id, because the tentative parse logic will try to resolve
   // names, and must treat them as unevaluated.
-  EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated,
-                                               Sema::ReuseLambdaContextDecl);
+  EnterExpressionEvaluationContext Unevaluated(
+      Actions, Sema::ExpressionEvaluationContext::Unevaluated,
+      Sema::ReuseLambdaContextDecl);
 
   if (isTypeIdInParens()) {
     TypeResult Ty = ParseTypeName();
@@ -1469,7 +1470,8 @@ ExprResult Parser::ParseCXXUuidof() {
                                     Ty.get().getAsOpaquePtr(), 
                                     T.getCloseLocation());
   } else {
-    EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
+    EnterExpressionEvaluationContext Unevaluated(
+        Actions, Sema::ExpressionEvaluationContext::Unevaluated);
     Result = ParseExpression();
 
     // Match the ')'.

lib/Parse/ParseStmt.cpp

@@ -1179,7 +1179,8 @@ StmtResult Parser::ParseIfStatement(SourceLocation *TrailingElseLoc) {
   StmtResult ThenStmt;
   {
     EnterExpressionEvaluationContext PotentiallyDiscarded(
-        Actions, Sema::DiscardedStatement, nullptr, false,
+        Actions, Sema::ExpressionEvaluationContext::DiscardedStatement, nullptr,
+        false,
         /*ShouldEnter=*/ConstexprCondition && !*ConstexprCondition);
     ThenStmt = ParseStatement(&InnerStatementTrailingElseLoc);
   }
@@ -1212,7 +1213,8 @@ StmtResult Parser::ParseIfStatement(SourceLocation *TrailingElseLoc) {
                           Tok.is(tok::l_brace));
 
     EnterExpressionEvaluationContext PotentiallyDiscarded(
-        Actions, Sema::DiscardedStatement, nullptr, false,
+        Actions, Sema::ExpressionEvaluationContext::DiscardedStatement, nullptr,
+        false,
         /*ShouldEnter=*/ConstexprCondition && *ConstexprCondition);
     ElseStmt = ParseStatement();
 

lib/Parse/ParseTemplate.cpp

@@ -701,8 +701,8 @@ Parser::ParseNonTypeTemplateParameter(unsigned Depth, unsigned Position) {
     //   end of the template-parameter-list rather than a greater-than
     //   operator.
     GreaterThanIsOperatorScope G(GreaterThanIsOperator, false);
-    EnterExpressionEvaluationContext ConstantEvaluated(Actions,
-                                                       Sema::ConstantEvaluated);
+    EnterExpressionEvaluationContext ConstantEvaluated(
+        Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
 
     DefaultArg = Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression());
     if (DefaultArg.isInvalid())
@@ -1275,7 +1275,8 @@ bool Parser::IsTemplateArgumentList(unsigned Skip) {
 bool
 Parser::ParseTemplateArgumentList(TemplateArgList &TemplateArgs) {
   // Template argument lists are constant-evaluation contexts.
-  EnterExpressionEvaluationContext EvalContext(Actions,Sema::ConstantEvaluated);
+  EnterExpressionEvaluationContext EvalContext(
+      Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
   ColonProtectionRAIIObject ColonProtection(*this, false);
 
   do {

lib/Sema/Sema.cpp

@@ -122,8 +122,9 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
   // Tell diagnostics how to render things from the AST library.
   Diags.SetArgToStringFn(&FormatASTNodeDiagnosticArgument, &Context);
 
-  ExprEvalContexts.emplace_back(PotentiallyEvaluated, 0, CleanupInfo{}, nullptr,
-                                false);
+  ExprEvalContexts.emplace_back(
+      ExpressionEvaluationContext::PotentiallyEvaluated, 0, CleanupInfo{},
+      nullptr, false);
 
   FunctionScopes.push_back(new FunctionScopeInfo(Diags));
 

lib/Sema/SemaDecl.cpp

@@ -10850,7 +10850,8 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
     // Regardless, we don't want to ignore array nesting when
     // constructing this copy.
     if (type->isStructureOrClassType()) {
-      EnterExpressionEvaluationContext scope(*this, PotentiallyEvaluated);
+      EnterExpressionEvaluationContext scope(
+          *this, ExpressionEvaluationContext::PotentiallyEvaluated);
       SourceLocation poi = var->getLocation();
       Expr *varRef =new (Context) DeclRefExpr(var, false, type, VK_LValue, poi);
       ExprResult result