f40c999f68
as suggested in <https://leanprover.zulipchat.com/#narrow/stream/270676-lean4/topic/termination_by.20regression/near/419786430> Also refactored the code a bit and removed the code smell around `GuessLex`-produced termination arguments (which may not be surface-syntactically expressible) a bit by introducing an explicit flag for those.
135 lines
3.5 KiB
Text
135 lines
3.5 KiB
Text
/-!
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Here we test that lean correctly complains if `termination_by` has too many variables,
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and that it does the right thing if it has fewer variables.
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-/
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opaque dec1 : Nat → Nat
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axiom dec1_lt (n : Nat) : dec1 n < n
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opaque dec2 : Nat → Nat
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axiom dec2_lt (n : Nat) : dec2 n < n
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namespace Basic
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def tooManyVars (n : Nat) : Nat := tooManyVars (dec1 n)
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termination_by x => x -- Error
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decreasing_by apply dec1_lt
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def okVariables1 (n : Nat) : Nat := okVariables1 (dec1 n)
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termination_by n
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decreasing_by apply dec1_lt
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def blankArrow (n : Nat) : Nat := blankArrow (dec1 n)
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termination_by => x -- Error
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decreasing_by apply dec1_lt
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def fewerVariables1 (n : Nat) : Nat → Nat → Nat := fun a b => fewerVariables1 (dec2 n) a (dec1 b)
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termination_by n -- Not an error
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decreasing_by apply dec2_lt
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def fewerVariables2 (n : Nat) : Nat → Nat → Nat := fun a b => fewerVariables2 n (dec1 a) (dec2 b)
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termination_by a => a
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decreasing_by apply dec1_lt -- NB: dec2_lt would no work
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def okVariables2 (n : Nat) : Nat → Nat → Nat := fun a b => okVariables2 n (dec1 a) (dec2 b)
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termination_by a b => b
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decreasing_by apply dec2_lt
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def tooManyVariables2 (n : Nat) : Nat → Nat → Nat := fun a b => tooManyVariables2 n (dec1 a) (dec2 b)
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termination_by a b c => b
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decreasing_by apply dec1_lt
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end Basic
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namespace WithVariable
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variable (v : Nat)
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def tooManyVars (n : Nat) : Nat := tooManyVars (dec1 n) + v
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termination_by x => x -- Error
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decreasing_by apply dec1_lt
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def okVariables1 (n : Nat) : Nat := okVariables1 (dec1 n) + v
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termination_by n
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decreasing_by apply dec1_lt
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def blankArrow (n : Nat) : Nat := blankArrow (dec1 n) + v
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termination_by => x -- Error
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decreasing_by apply dec1_lt
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def fewerVariables1 (n : Nat) : Nat → Nat → Nat := fun a b =>
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fewerVariables1 (dec2 n) a (dec1 b) + v
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termination_by n
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decreasing_by apply dec2_lt
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def fewerVariables2 (n : Nat) : Nat → Nat → Nat := fun a b =>
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fewerVariables2 n (dec1 a) (dec2 b) + v
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termination_by a => a
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decreasing_by apply dec1_lt
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def okVariables2 (n : Nat) : Nat → Nat → Nat := fun a b =>
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okVariables2 n a (dec1 b) + v
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termination_by a b => b
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decreasing_by apply dec1_lt
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end WithVariable
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namespace InLetRec
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def foo1 (v : Nat) := 5
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where
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tooManyVars (n : Nat) : Nat := tooManyVars (dec1 n) + v
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termination_by x => x -- Error
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decreasing_by apply dec1_lt
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def foo2 (v : Nat) := 5
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where
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okVariables1 (n : Nat) : Nat := okVariables1 (dec1 n) + v
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termination_by n
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decreasing_by apply dec1_lt
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def foo3 (v : Nat) := 5
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where
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blankArrow (n : Nat) : Nat := blankArrow (dec1 n) + v
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termination_by => x -- Error
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decreasing_by apply dec1_lt
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def foo4 (v : Nat) := 5
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where
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fewerVariables1 (n : Nat) : Nat → Nat → Nat := fun a b =>
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fewerVariables1 (dec2 n) a (dec1 b) + v
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termination_by n
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decreasing_by apply dec2_lt
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def foo5 (v : Nat) := 5
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where
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fewerVariables2 (n : Nat) : Nat → Nat → Nat := fun a b =>
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fewerVariables2 n (dec1 a) (dec2 b) + v
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termination_by a => a
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decreasing_by apply dec1_lt
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def foo6 (v : Nat) := 5
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where
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okVariables2 (n : Nat) : Nat → Nat → Nat := fun a b =>
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okVariables2 n a (dec1 b) + v
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termination_by a b => b
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decreasing_by apply dec1_lt
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end InLetRec
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namespace ManyTooMany
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def tooManyVars (n : Nat) : Nat := tooManyVars (dec1 n)
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termination_by x y z => x -- Error
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decreasing_by apply dec1_lt
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end ManyTooMany
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namespace WithHelpfulComment
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def foo (n : Nat) : Nat := foo (dec1 n)
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termination_by foo n => n -- Error
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decreasing_by apply dec1_lt
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end WithHelpfulComment
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