Standardize on SymbolInfo.None vs. default(SymbolInfo)

Fixes #9261.

src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs

@@ -4616,7 +4616,7 @@ protected sealed override SymbolInfo GetSpeculativeSymbolInfoCore(int position,
             }
             else
             {
-                return default(SymbolInfo);
+                return SymbolInfo.None;
             }
         }
 
@@ -4624,7 +4624,7 @@ protected sealed override TypeInfo GetSpeculativeTypeInfoCore(int position, Synt
         {
             return expression is ExpressionSyntax
                 ? GetSpeculativeTypeInfo(position, (ExpressionSyntax)expression, bindingOption)
-                : default(TypeInfo);
+                : CSharpTypeInfo.None;
         }
 
         protected sealed override IAliasSymbol GetSpeculativeAliasInfoCore(int position, SyntaxNode nameSyntax, SpeculativeBindingOption bindingOption)

src/Compilers/CSharp/Portable/Compilation/MemberSemanticModel.cs

@@ -799,7 +799,7 @@ private BoundQueryClause GetBoundQueryClause(CSharpSyntaxNode node)
         private QueryClauseInfo GetQueryClauseInfo(BoundQueryClause bound)
         {
             if (bound == null) return default(QueryClauseInfo);
-            var castInfo = (bound.Cast == null) ? default(SymbolInfo) : GetSymbolInfoForNode(SymbolInfoOptions.DefaultOptions, bound.Cast, bound.Cast, boundNodeForSyntacticParent: null, binderOpt: null);
+            var castInfo = (bound.Cast == null) ? SymbolInfo.None : GetSymbolInfoForNode(SymbolInfoOptions.DefaultOptions, bound.Cast, bound.Cast, boundNodeForSyntacticParent: null, binderOpt: null);
             var operationInfo = GetSymbolInfoForQuery(bound);
             return new QueryClauseInfo(castInfo: castInfo, operationInfo: operationInfo);
         }
@@ -809,7 +809,7 @@ private SymbolInfo GetSymbolInfoForQuery(BoundQueryClause bound)
             var call = bound?.Operation as BoundCall;
             if (call == null)
             {
-                return default(SymbolInfo);
+                return SymbolInfo.None;
             }
 
             var operation = call.IsDelegateCall ? call.ReceiverOpt : call;

src/Compilers/CSharp/Portable/Compilation/SyntaxTreeSemanticModel.cs

@@ -419,14 +419,14 @@ public override SymbolInfo GetSymbolInfo(SelectOrGroupClauseSyntax node, Cancell
         {
             CheckSyntaxNode(node);
             var model = this.GetMemberModel(node);
-            return (model == null) ? default(SymbolInfo) : model.GetSymbolInfo(node, cancellationToken);
+            return (model == null) ? SymbolInfo.None : model.GetSymbolInfo(node, cancellationToken);
         }
 
         public override TypeInfo GetTypeInfo(SelectOrGroupClauseSyntax node, CancellationToken cancellationToken = default(CancellationToken))
         {
             CheckSyntaxNode(node);
             var model = this.GetMemberModel(node);
-            return (model == null) ? default(TypeInfo) : model.GetTypeInfo(node, cancellationToken);
+            return (model == null) ? CSharpTypeInfo.None : model.GetTypeInfo(node, cancellationToken);
         }
 
         public override IPropertySymbol GetDeclaredSymbol(AnonymousObjectMemberDeclaratorSyntax declaratorSyntax, CancellationToken cancellationToken = default(CancellationToken))
@@ -482,7 +482,7 @@ public override SymbolInfo GetSymbolInfo(OrderingSyntax node, CancellationToken
         {
             CheckSyntaxNode(node);
             var model = this.GetMemberModel(node);
-            return (model == null) ? default(SymbolInfo) : model.GetSymbolInfo(node, cancellationToken);
+            return (model == null) ? SymbolInfo.None : model.GetSymbolInfo(node, cancellationToken);
         }
 
         private ConsList<Symbol> GetBasesBeingResolved(TypeSyntax expression)