[libcxx-commits] [clang] [libcxx] [Clang] Normalize constraints before checking for satisfaction (PR #141776)

[Corentin Jabot via libcxx-commits]

================
@@ -16,130 +16,385 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Expr.h"
+#include "clang/AST/ExprConcepts.h"
 #include "clang/Basic/SourceLocation.h"
+#include "clang/Sema/Ownership.h"
 #include "llvm/ADT/FoldingSet.h"
-#include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/STLFunctionalExtras.h"
+#include "llvm/ADT/SmallBitVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include <optional>
 #include <utility>
 
 namespace clang {
 class Sema;
+class MultiLevelTemplateArgumentList;
 
-enum { ConstraintAlignment = 8 };
+/// \brief A normalized constraint, as defined in C++ [temp.constr.normal], is
+/// either an atomic constraint, a conjunction of normalized constraints or a
+/// disjunction of normalized constraints.
+struct NormalizedConstraint {
+
+  enum class ConstraintKind : unsigned char {
+    Atomic = 0,
+    ConceptId,
+    FoldExpanded,
+    Compound,
+  };
+
+  enum CompoundConstraintKind : unsigned char {
+    CCK_Conjunction,
+    CCK_Disjunction
+  };
+  enum class FoldOperatorKind : unsigned char { And, Or };
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cor3ntin wrote:

They all are different things. I would prefer they remain separate to match the wording

A constraint can be either a Compound constraint, or a FoldExpanded constraint.
a Compound constraint can be either a conjunction or a disjunction.

a FoldExpanded has an operator. the reason we have an enum for that instead of reusing `BinaryOperatorKind` is that we don't need/want to use more than one bits (and none of the operator produce a fold expanded constraint)
 

https://github.com/llvm/llvm-project/pull/141776