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LDC-E2117 — A text pattern outside the supported grammar

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# LDC-E2117 — A text pattern outside the supported grammar

## What it means

Text matching uses a bounded pattern grammar: only the pattern shapes
the language defines are accepted. A pattern that breaks that grammar —
an unclosed class, a stray operator — cannot be compiled, so the
compiler rejects it at the literal and says which part went wrong.

Closing the class, escaping the stray character, or otherwise bringing
the pattern back inside the supported shapes fixes it. The message
quotes the offending pattern, so the repair starts there.

## Example

```law
language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity Akt;
relation value_of(a: Akt, v: Text) kind empirical;
relation ok(a: Akt) kind institutional;
rule R(a: Akt, v: Text) strict {
  when value_of(a, v) and text_matches(v, "[0-9");
  then ok(a);
}
```

## Fix

```law
language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity Akt;
relation value_of(a: Akt, v: Text) kind empirical;
relation ok(a: Akt) kind institutional;
rule R(a: Akt, v: Text) strict {
  when value_of(a, v) and text_matches(v, "[0-9]+");
  then ok(a);
}
```

## Engine message

The engine reports this in its own wording:

```text
example.law:9:43: error LDC-E2117: text_matches: pattern «[0-9» violates the §257.1 grammar: unclosed class `[`
```

## Related

- [Expressions and quantities](/constructs/expressions-quantities/) — how text matching is written.