[NFC] Simplify some code using ValueDecl::getParameterList

Author: AnthonyLatsis

lib/AST/NameLookup.cpp

@@ -3710,13 +3710,14 @@ createOpaqueParameterGenericParams(GenericContext *genericContext, GenericParamL
     return { };
 
   // Functions, initializers, and subscripts can contain opaque parameters.
-  ParameterList *params = nullptr;
-  if (auto func = dyn_cast<AbstractFunctionDecl>(value))
-    params = func->getParameters();
-  else if (auto subscript = dyn_cast<SubscriptDecl>(value))
-    params = subscript->getIndices();
-  else
+  // FIXME: What's wrong with allowing them in macro decls?
+  if (isa<MacroDecl>(value)) {
     return { };
+  }
+  auto *params = value->getParameterList();
+  if (!params) {
+    return {};
+  }
 
   // Look for parameters that have "some" types in them.
   unsigned index = parsedGenericParams ? parsedGenericParams->size() : 0;

lib/Sema/TypeCheckConcurrency.cpp

@@ -7262,7 +7262,7 @@ static AnyFunctionType *applyUnsafeConcurrencyToFunctionType(
 
   SmallVector<AnyFunctionType::Param, 4> newTypeParams;
   auto typeParams = fnType->getParams();
-  auto paramDecls = func ? func->getParameters() : subscript->getIndices();
+  auto paramDecls = decl->getParameterList();
   assert(typeParams.size() == paramDecls->size());
   bool knownUnsafeParams = func && hasKnownUnsafeSendableFunctionParams(func);
   bool stripConcurrency =

lib/Sema/TypeCheckGeneric.cpp

@@ -714,10 +714,8 @@ GenericSignatureRequest::evaluate(Evaluator &evaluator,
                                         /*unboundTyOpener*/ nullptr,
                                         /*placeholderHandler*/ nullptr,
                                         /*packElementOpener*/ nullptr);
-      auto params = func ? func->getParameters()
-                      : subscr ? subscr->getIndices()
-                      : macro->parameterList;
-      for (auto param : *params) {
+
+      for (auto param : *VD->getParameterList()) {
         auto *typeRepr = param->getTypeRepr();
         if (typeRepr == nullptr)
             continue;