In a single match step, we match the first discriminant against the "head" of the first pattern of the first alternative. This datatype describes what kind of check this involves, which helps other patterns decide if they are covered by the same check and don't have to be checked again (see also MatchResult).

unconditional : HeadCheck
match step that always succeeds: _, x, `($x), ...
shape (k : List SyntaxNodeKind) (arity : Option Nat) : HeadCheck
match step based on kind and, optionally, arity of discriminant If arity is given, that number of new discriminants is introduced. covered patterns should then introduce the same number of new patterns. We actually check the arity at run time only in the case of null nodes since it should otherwise by implied by the node kind. without arity: `($x:k) with arity: any quotation without an antiquotation head pattern
slice (numPrefix numSuffix : Nat) : HeadCheck
Match step that succeeds on null nodes of arity at least numPrefix + numSuffix, introducing discriminants for the first numPrefix children, one null node for those in between, and for the numSuffix last children. example: ([$x, $xs,*, $y]) is slice 2 2`
other (pat : Syntax) : HeadCheck
other, complicated match step that will probably only cover identical patterns example: antiquotation splices `($[...]*)

Instances For

source

inductive Lean.Elab.Term.Quotation.MatchResult :

Type

Describe whether a pattern is covered by a head check (induced by the pattern itself or a different pattern).

covered (f : Alt → TermElabM Alt) (exhaustive : Bool) : MatchResult
Pattern agrees with head check, remove and transform remaining alternative. If exhaustive is false, also include unchanged alternative in the "no" branch.
uncovered : MatchResult
Pattern disagrees with head check, include in "no" branch only
undecided : MatchResult
Pattern is not quite sure yet; include unchanged in both branches

Instances For

source

@[implicit_reducible]

instance Lean.Elab.Term.Quotation.instReprMatchResult :

Repr MatchResult

source

structure Lean.Elab.Term.Quotation.HeadInfo :

Type

All necessary information on a pattern head.

check : HeadCheck
check induced by the pattern
onMatch (taken : HeadCheck) : MatchResult
compute compatibility of pattern with given head check
doMatch (yes : List Term → TermElabM Term) (no : TermElabM Term) : TermElabM Term
actually run the specified head check, with the discriminant bound to __discr