Typed filters double braces in string literals: x.Code != "{draft}" renders '{{draft}}' #70

Problem

A string literal containing { or } in a typed filter is stored with the braces doubled, and filters never undo that: ResolveFilter deliberately has no {{ escape, because '{{1,2},{3,4}}' is a valid PostgreSQL array literal.

b.HasComplexIndex(x => x.Code, x => x.Code != "{draft}", indexName: "ix_code_final");

scaffolds

CREATE INDEX "ix_code_final" ON ... ("Code") WHERE "Code" <> '{{draft}}';

On PostgreSQL SELECT '{draft}' <> '{{draft}}' is true, so rows whose code is {draft} are indexed, and constrained if the index is unique, while the model says they are excluded. No error at migrations add or at apply. The same goes for HasFilter<T>, AddComplexIndexFilter<T> and typed exclusion-constraint filters.

The doubling is right for typed expression indexes (NpgsqlLinqIndexTranslator.Translate), whose templates are unescaped when resolved; it is wrong for predicates, which go through the filter resolver.

Fix

Predicate literals keep their braces: TranslatePredicate must not escape braces inside string literals. ResolveFilter already skips everything inside single quotes, so an unescaped brace there can never be read as a placeholder.

Changed answer

A typed filter with a brace in a string literal re-creates its index or constraint on the first migrations add after upgrading. Ships in a minor with a ### Changed answers row.

Found by the 5.5.0 pre-tag analysis (code-analyst, PostgreSQL satellite). Present since typed filters shipped in 5.2.0.