Make deriveProtocolRequirement a static utility

Author: CodaFi

lib/Sema/TypeCheckProtocol.cpp

@@ -3358,7 +3358,8 @@ ResolveWitnessResult ConformanceChecker::resolveWitnessViaDerivation(
   }
 
   // Attempt to derive the witness.
-  auto derived = TC.deriveProtocolRequirement(DC, derivingTypeDecl, requirement);
+  auto derived =
+      TypeChecker::deriveProtocolRequirement(DC, derivingTypeDecl, requirement);
   if (!derived)
     return ResolveWitnessResult::ExplicitFailed;
 

lib/Sema/TypeChecker.h

@@ -1550,9 +1550,9 @@ class TypeChecker final : public LazyResolver {
   /// \returns nullptr if the derivation failed, or the derived declaration
   ///          if it succeeded. If successful, the derived declaration is added
   ///          to TypeDecl's body.
-  ValueDecl *deriveProtocolRequirement(DeclContext *DC,
-                                       NominalTypeDecl *TypeDecl,
-                                       ValueDecl *Requirement);
+  static ValueDecl *deriveProtocolRequirement(DeclContext *DC,
+                                              NominalTypeDecl *TypeDecl,
+                                              ValueDecl *Requirement);
 
   /// Derive an implicit type witness for the given associated type in
   /// the conformance of the given nominal type to some known