Sema: isPassThroughTypealias() is only used in one file

Author: slavapestov

lib/Sema/TypeCheckDecl.cpp

@@ -4689,7 +4689,25 @@ void TypeChecker::finalizeDecl(ValueDecl *decl) {
   (void)decl->isDynamic();
 }
 
-bool swift::isPassThroughTypealias(TypeAliasDecl *typealias) {
+/// Determine whether this is a "pass-through" typealias, which has the
+/// same type parameters as the nominal type it references and specializes
+/// the underlying nominal type with exactly those type parameters.
+/// For example, the following typealias \c GX is a pass-through typealias:
+///
+/// \code
+/// struct X<T, U> { }
+/// typealias GX<A, B> = X<A, B>
+/// \endcode
+///
+/// whereas \c GX2 and \c GX3 are not pass-through because \c GX2 has
+/// different type parameters and \c GX3 doesn't pass its type parameters
+/// directly through.
+///
+/// \code
+/// typealias GX2<A> = X<A, A>
+/// typealias GX3<A, B> = X<B, A>
+/// \endcode
+static bool isPassThroughTypealias(TypeAliasDecl *typealias) {
   // Pass-through only makes sense when the typealias refers to a nominal
   // type.
   Type underlyingType = typealias->getUnderlyingTypeLoc().getType();

lib/Sema/TypeChecker.h

@@ -2171,26 +2171,6 @@ bool isAcceptableDynamicMemberLookupSubscript(SubscriptDecl *decl,
                                               DeclContext *DC,
                                               TypeChecker &TC);
 
-/// Determine whether this is a "pass-through" typealias, which has the
-/// same type parameters as the nominal type it references and specializes
-/// the underlying nominal type with exactly those type parameters.
-/// For example, the following typealias \c GX is a pass-through typealias:
-///
-/// \code
-/// struct X<T, U> { }
-/// typealias GX<A, B> = X<A, B>
-/// \endcode
-///
-/// whereas \c GX2 and \c GX3 are not pass-through because \c GX2 has
-/// different type parameters and \c GX3 doesn't pass its type parameters
-/// directly through.
-///
-/// \code
-/// typealias GX2<A> = X<A, A>
-/// typealias GX3<A, B> = X<B, A>
-/// \endcode
-bool isPassThroughTypealias(TypeAliasDecl *typealias);
-
 /// Whether an overriding declaration requires the 'override' keyword.
 enum class OverrideRequiresKeyword {
   /// The keyword is never required.