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Code actions for typed holes and incomplete matches

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The language server can fill a hole with what fits it and add the
clauses a match lacks; the sections on typed holes and exhaustiveness
say so.

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Co-Authored-By: eca-agent <git@eca.dev>
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Linus Björnstam 2026-10-22 20:35:00 +02:00
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_01.Language-basics.sz
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@ -185,6 +185,8 @@ The bindings closest to the hole are listed first: locals, then your own module'
While a hole's type is still open, the other errors in the same definition are held back, since they are often caused by the hole. Once you fill it in, they show up. While a hole's type is still open, the other errors in the same definition are held back, since they are often caused by the hole. Once you fill it in, they show up.
In an editor that uses the Bjolang language server, a hole has code actions: fill it with one of the bindings that fit, with a constructor of its type such as @code{(Circle _)}, or, where a function is wanted, with @code{(fun (x y) _)}. What you fill in can have holes of its own, so you can build an expression a step at a time and let the compiler tell you what each part has to be.
@subsubsection{Unused definitions} @subsubsection{Unused definitions}
The compiler warns about definitions nothing uses: a top-level @code{def} or @code{defun} that the module doesn't export and nothing in it reads, and a local binding (a @code{let}, a @code{def} in a body, a loop variable) that nothing in its scope reads. Dead code piles up quietly in a large program, and this keeps it from doing so. The compiler warns about definitions nothing uses: a top-level @code{def} or @code{defun} that the module doesn't export and nothing in it reads, and a local binding (a @code{let}, a @code{def} in a body, a loop variable) that nothing in its scope reads. Dead code piles up quietly in a large program, and this keeps it from doing so.
@ -977,6 +979,8 @@ The counterexample is a real value, and for nested patterns it tells you exactly
Pattern Error at cards.bjo:8: this match does not cover every value. (Card (rank Ace) (suit Clubs)) reaches no clause. Pattern Error at cards.bjo:8: this match does not cover every value. (Card (rank Ace) (suit Clubs)) reaches no clause.
}| }|
In an editor that uses the Bjolang language server, an incomplete match has a code action that adds the clauses it lacks, nested cases spelled out, each with a typed hole as its body: @code{((Square _) _)}.
A clause that can never run, because the clauses above it already match everything it would, is also an error: A clause that can never run, because the clauses above it already match everything it would, is also an error:
@codeblock[#:lang "text"]|{ @codeblock[#:lang "text"]|{