[Sema] NFC: Remove diagnoseMoveOnlyPatternMatchSubject

This appears to be a dead function now.

Author: hamishknight

lib/Sema/MiscDiagnostics.cpp

@@ -4407,30 +4407,9 @@ void swift::performAbstractFuncDeclDiagnostics(AbstractFunctionDecl *AFD) {
   }
 }
 
-static void
-diagnoseMoveOnlyPatternMatchSubject(ASTContext &C,
-                                    const DeclContext *DC,
-                                    Expr *subjectExpr) {
-  // For now, move-only types must use the `consume` operator to be
-  // pattern matched. Pattern matching is only implemented as a consuming
-  // operation today, but we don't want to be stuck with that as the default
-  // in the fullness of time when we get borrowing pattern matching later.
-  
-  // Don't bother if the subject wasn't given a valid type, or is a copyable
-  // type.
-  auto subjectType = subjectExpr->getType();
-  if (!subjectType
-      || subjectType->hasError()
-      || !subjectType->isNoncopyable()) {
-    return;
-  }
-}
-
 // Perform MiscDiagnostics on Switch Statements.
 static void checkSwitch(ASTContext &ctx, const SwitchStmt *stmt,
                         DeclContext *DC) {
-  diagnoseMoveOnlyPatternMatchSubject(ctx, DC, stmt->getSubjectExpr());
-                        
   // We want to warn about "case .Foo, .Bar where 1 != 100:" since the where
   // clause only applies to the second case, and this is surprising.
   for (auto cs : stmt->getCases()) {
@@ -5184,9 +5163,7 @@ static void checkLabeledStmtConditions(ASTContext &ctx,
 
     switch (elt.getKind()) {
     case StmtConditionElement::CK_Boolean:
-      break;
     case StmtConditionElement::CK_PatternBinding:
-      diagnoseMoveOnlyPatternMatchSubject(ctx, DC, elt.getInitializer());
       break;
     case StmtConditionElement::CK_Availability: {
       auto info = elt.getAvailability();