8424ddbb3e
This PR improves the “expected type mismatch” error message by omitting the type's types when they are defeq, and putting them into separate lines when not. I found it rather tediuos to parse the error message when the expected type is long, because I had to find the `:` in the middle of a large expression somewhere. Also, when both are of sort `Prop` or `Type` it doesn't add much value to print the sort (and it’s only one hover away anyways).
105 lines
1.8 KiB
Text
105 lines
1.8 KiB
Text
/-!
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# Better `calc` error messages
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RFC https://github.com/leanprover/lean4/issues/4318
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-/
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axiom testSorry {α : Sort _} : α
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/-!
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Term-mode `calc`. Errors about LHS and RHS not matching expected type.
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-/
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/--
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error: invalid 'calc' step, left-hand side is
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1 + n - n : Nat
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but is expected to be
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0 : Nat
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-/
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#guard_msgs in
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example (n : Nat) : 0 = 1 :=
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calc
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1 + n - n = 1 := testSorry
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/--
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error: invalid 'calc' step, right-hand side is
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n - n : Nat
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but is expected to be
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1 : Nat
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-/
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#guard_msgs in
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example (n : Nat) : 0 = 1 :=
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calc
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0 = n - n := testSorry
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/--
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error: 'calc' expression has type
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0 = 1
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but is expected to have type
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0 < 1
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-/
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#guard_msgs in
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example : 0 < 1 :=
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calc
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0 = 1 := testSorry
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/-!
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Tactic-mode `calc`. LHS failure.
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-/
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/--
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error: invalid 'calc' step, left-hand side is
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1 + n - n : Nat
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but is expected to be
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0 : Nat
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-/
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#guard_msgs in
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example (n : Nat) : 0 = 1 := by
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calc
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1 + n - n = 1 := testSorry
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/-!
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Tactic mode `calc`. RHS failure, but calc extension succeeds.
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-/
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example (n : Nat) : 0 ≤ 1 := by
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calc 0
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_ ≤ n - n := testSorry
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guard_target =ₛ n - n ≤ 1
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exact testSorry
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/-!
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Tactic mode `calc`. Calc extension fails due to expected type mismatch, so report original failure.
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-/
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/--
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error: 'calc' expression has type
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0 < n - n
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but is expected to have type
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0 ≤ 1
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-/
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#guard_msgs in
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example (n : Nat) : 0 ≤ 1 := by
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calc
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0 < n - n := testSorry
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/-!
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Tactic mode `calc`. Calc extension fails due to nontransitivity, so report original failure.
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-/
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/--
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error: invalid 'calc' step, right-hand side is
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1 : Nat
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but is expected to be
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2 : Nat
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-/
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#guard_msgs in
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example (n : Nat) : 0 ≠ 2 := by
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calc 0
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_ ≠ 1 := testSorry
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/-!
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Tactic mode `calc`. Calc extension succeeds.
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-/
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#guard_msgs in
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example : 0 < 1 := by
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calc 0
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_ ≤ 1 := testSorry
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guard_target =ₛ 1 < 1
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exact testSorry
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