# JETLS warning \`md\` is not concretized

**URL:** https://discourse.julialang.org/t/jetls-warning-md-is-not-concretized/134820
**Category:** General Usage
**Tags:** question, package, jetls
**Created:** [December 31, 2025, 8:42pm UTC](https://discourse.julialang.org/t/jetls-warning-md-is-not-concretized/134820 "2025-12-31T20:42:07Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)
#### Post date: [December 31, 2025, 8:42pm UTC](https://discourse.julialang.org/t/jetls-warning-md-is-not-concretized/134820/1 "2025-12-31T20:42:07Z")

</div>

I have a script that contains the lines:

```julia-auto
using DataFrames
md::DataFrame = DataFrame()
...

```

I get the following JETLS.jl warning:

```julia-auto
`md` is not concretized but JET needs to use its actual value in order to define types or methods.
- If this binding can be declared as a constant, try to declare it as a constant (i.e. `const md = ...`).
- You may need to specify `:(md = x_)` pattern to the `concretization_patterns`
  configuration to allow JET to actually evaluate this binding, e.g.,
  `report_file("path/to/file.jl"; concretization_patterns = [:(md = x_)])`.
- If the above approaches do not work, try `concretization_patterns = [:(x_)]` to
  concretize all top-level code in the module (recommended as a last resort since it
  would incur any side effects in your code and may cause the analysis to take longer time).

```

I would like to fix it. The variable is not constant, but the type is. But what should I add to my configuration file `.JETLSConfig.toml`?

I tried:

```julia-auto
concretization_patterns = [
    ":(md = x_)"
]

```

But that does not fix the warning.

---

<div class="post-metadata">

### Author: ![jling](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jling/32/212909_2.png) [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [January 1, 2026, 1:22am UTC](https://discourse.julialang.org/t/jetls-warning-md-is-not-concretized/134820/2 "2026-01-01T01:22:32Z")

</div>

idk if this would work but the message says

```julia-auto
[:(md = x_)])

```

not `["..."]`

---

<div class="post-metadata">

### Author: ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)
#### Post date: [January 1, 2026, 1:30am UTC](https://discourse.julialang.org/t/jetls-warning-md-is-not-concretized/134820/3 "2026-01-01T01:30:37Z")

</div>

The point is, I think the message provides Julia code and not YAML. It is likely a message intended for JET users, rather than JETLS users.