f771dea78b
This PR fixes an issue where the "eta feature" in the app elaborator, which is invoked when positional arguments are skipped due to named arguments, results in variables that can be captured by those named arguments. Now the temporary local variables that implement this feature get fresh names. The names used for the closed lambda expression still use the original parameter names. Closes #6373
50 lines
1.2 KiB
Text
50 lines
1.2 KiB
Text
/-!
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# Test for issue 6373, variable capture for app elaborator eta feature
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https://github.com/leanprover/lean4/issues/6373
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-/
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def sum3 (x y z : Nat) : Nat := x + y + z
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/-!
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The following two used to elaborate differently.
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Now in the second, we can see that the `x` in the `fun` (from the eta feature), does not shadow the `x` in the `let`.
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Note that in both, `y` can still be used as a named argument.
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-/
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/--
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info: fun x =>
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(let w := 15;
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fun x y => sum3 x y w)
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x 3 : Nat → Nat
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-/
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#guard_msgs in
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#check (let w := 15; sum3 (z := w)) (y := 3)
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/--
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info: fun x =>
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(let x := 15;
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fun x_1 y => sum3 x_1 y x)
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x 3 : Nat → Nat
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-/
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#guard_msgs in
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#check (let x := 15; sum3 (z := x)) (y := 3)
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/-!
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Verifying that each evaluates to the same value when evaluated at `0`.
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The second used to evaluate to `3` instead of `18`.
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-/
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/-- info: 18 -/
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#guard_msgs in
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#eval (let w := 15; sum3 (z := w)) (y := 3) <| 0
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/-- info: 18 -/
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#guard_msgs in
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#eval (let x := 15; sum3 (z := x)) (y := 3) <| 0
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/-!
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Same verification, but make sure that `0` can be passed as a named argument.
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-/
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/-- info: 18 -/
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#guard_msgs in
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#eval (let w := 15; sum3 (z := w)) (y := 3) (x := 0)
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/-- info: 18 -/
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#guard_msgs in
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#eval (let x := 15; sum3 (z := x)) (y := 3) (x := 0)
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