Revert "[Concepts] Constraint Enforcement & Diagnostics"

This reverts commit ffa214ef22892d75340dc6720271863901dc2c90, it was
causing ASAN test failures on sanitizer-x86_64-linux-bootstrap.
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index f5d659a..a275e0c 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -12,7 +12,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Serialization/ASTReader.h"
-#include "clang/AST/ASTConcept.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/AttrIterator.h"
 #include "clang/AST/Decl.h"
@@ -743,33 +742,14 @@
   E->TemplateKWLoc = Record.readSourceLocation();
   E->ConceptNameLoc = Record.readSourceLocation();
   E->FoundDecl = ReadDeclAs<NamedDecl>();
-  E->NamedConcept = ReadDeclAs<ConceptDecl>();
+  E->NamedConcept.setPointer(ReadDeclAs<ConceptDecl>());
   const ASTTemplateArgumentListInfo *ArgsAsWritten =
       Record.readASTTemplateArgumentListInfo();
   llvm::SmallVector<TemplateArgument, 4> Args;
   for (unsigned I = 0; I < NumTemplateArgs; ++I)
     Args.push_back(Record.readTemplateArgument());
   E->setTemplateArguments(ArgsAsWritten, Args);
-  ConstraintSatisfaction Satisfaction;
-  Satisfaction.IsSatisfied = Record.readInt();
-  if (!Satisfaction.IsSatisfied) {
-    unsigned NumDetailRecords = Record.readInt();
-    for (unsigned i = 0; i != NumDetailRecords; ++i) {
-      Expr *ConstraintExpr = Record.readExpr();
-      bool IsDiagnostic = Record.readInt();
-      if (IsDiagnostic) {
-        SourceLocation DiagLocation = Record.readSourceLocation();
-        std::string DiagMessage = Record.readString();
-        Satisfaction.Details.emplace_back(
-            ConstraintExpr, new (Record.getContext())
-                                ConstraintSatisfaction::SubstitutionDiagnostic{
-                                    DiagLocation, DiagMessage});
-      } else
-        Satisfaction.Details.emplace_back(ConstraintExpr, Record.readExpr());
-    }
-  }
-  E->Satisfaction = ASTConstraintSatisfaction::Create(Record.getContext(),
-                                                      Satisfaction);
+  E->NamedConcept.setInt(Record.readInt() == 1);
 }
 
 void ASTStmtReader::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {