Stubs

The checker has no R runtime, so it cannot look up what nchar() returns. It reads stubs: declaration-only files that describe a package’s types, the way rust-analyzer knows std without running it.

What ships

Only a small kernel is built in — the operators, plus c() and list(). Everything else comes from the shipped corpus:

	Namespaces
Fully typed	base, stats, utils, methods, graphics, grDevices, datasets — attached by default
Typed when your project uses them	data.table, dplyr, ggplot2, testthat
Export lists only	the tidyverse (and library(tidyverse) itself), knitr, rlang, glue, magrittr, scales, jsonlite, R6, and every namespace R ships

The difference between the last two rows matters. A typed namespace gives calls through it real types. An export list gives no types, but it does tell the checker which names exist — which is what keeps unresolved working, so a typo next to a real export is still caught.

When a package is not known

Attaching a package ry has never heard of weakens the unresolved check across the project: any bare name could be one of that package’s exports, so unresolved names are tolerated rather than reported.

Two things limit the damage. A near-miss of a name your own project binds is still reported — library(shiny) cannot explain repositry sitting next to a repository parameter. And strict = true makes every tolerated read visible.

The real fix is to declare the package yourself.

Teaching it about a package

Drop a .Rtypes file under stubs/ in your project. The file name is the namespace, so stubs/mypkg.Rtypes declares mypkg.

A couple of lines are enough to restore full checking for the names you actually use:

@type Session
connect: fn(host: character) -> Session

Stub declarations are bare — no #: prefix, and @type in a stub names an opaque type rather than giving it a representation. That is usually what you want for a package’s own objects: you care that connect() returns a Session and that a Session is not a character, not what is inside it.

That gives you three things at once: connect() gets a real signature, mypkg::connect validates as a known namespace, and the unknown-namespace warning goes away.

You do not have to describe the whole package. Declare what you call.

Overriding a shipped declaration

The same mechanism corrects the shipped corpus. A declaration in your stubs/ directory replaces the shipped one of the same name, so if a return type is wrong, or a name is missing for your version of a package, you can fix it locally without waiting for a release.

Overriding a name does not remove it from its own namespace: stats::sd stays valid under an sd override.

Nothing here fails silently. ry check reports every declaration it had to drop — a line that does not parse, or one naming a type that does not exist — as an error on that stub line, and your editor shows the same while the .Rtypes file is open.

Next

• Authoring stubs — the full declaration format, overload sets, and export manifests
• Limitations — what stubs cannot fix