AST: Don't kick off getGenericSignature() from computeCanonicalType()

Author: slavapestov

lib/AST/Type.cpp

@@ -1468,10 +1468,9 @@ CanType TypeBase::computeCanonicalType() {
     // If we haven't set a depth for this generic parameter, try to do so.
     // FIXME: This is a dreadful hack.
     if (gpDecl->getDepth() == GenericTypeParamDecl::InvalidDepth) {
-      if (auto decl =
-            gpDecl->getDeclContext()->getInnermostDeclarationDeclContext())
-        if (auto valueDecl = decl->getAsGenericContext())
-          (void)valueDecl->getGenericSignature();
+      auto *dc = gpDecl->getDeclContext();
+      auto *gpList = dc->getAsDecl()->getAsGenericContext()->getGenericParams();
+      gpList->setDepth(dc->getGenericContextDepth());
     }
 
     assert(gpDecl->getDepth() != GenericTypeParamDecl::InvalidDepth &&