3a309ba4eb
This PR improves the error message encountered in the case of a type class instance resolution failure, and adds an error explanation that discusses the common new-user case of binary operation overloading and points to the `trace.Meta.synthInstance` option for advanced debugging. ## Example ```lean4 def f (x : String) := x + x ``` Before: ``` failed to synthesize HAdd String String ?m.5 Hint: Additional diagnostic information may be available using the `set_option diagnostics true` command. ``` After: ``` failed to synthesize instance of type class HAdd String String ?m.5 Hint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command. Error code: lean.failedToSynthesizeTypeclassInstance [View explanation](https://lean-lang.org/doc/reference/latest/find/?domain=Manual.errorExplanation&name=lean.failedToSynthesizeTypeclassInstance) ``` The error message is changed in three important ways: * Explains *what* failed to synthesize, using the "type class" terminology that's more likely to be recognized than the "instance" terminology * Points to the `trace.Meta.synthInstance` option which is otherwise nearly undiscoverable but is quite powerful (see also leanprover/reference-manual#663 which is adding commentary on this option) * Gives an error explanation link (which won't actually work until the next release after this is merged) which prioritizes the common-case explanation of using the wrong binary operation
212 lines
4.9 KiB
Text
212 lines
4.9 KiB
Text
module
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prelude
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public import Module.Basic
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import Lean.DocString
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meta import Lean.Elab.Command
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/-! Definitions should be exported without their bodies by default -/
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/--
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info: def f : Nat :=
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<not imported>
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-/
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#guard_msgs in
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#print f
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/--
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error: Type mismatch
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rfl
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has type
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?m.5 = ?m.5
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but is expected to have type
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f = 1
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Note: The following definitions were not unfolded because their definition is not exposed:
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f ↦ 1
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-/
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#guard_msgs in
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example : f = 1 := rfl
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/--
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error: Tactic `apply` failed: could not unify the conclusion of `@rfl`
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?a = ?a
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with the goal
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f = 1
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Note: The full type of `@rfl` is
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∀ {α : Sort ?u.115} {a : α}, a = a
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Note: The following definitions were not unfolded because their definition is not exposed:
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f ↦ 1
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⊢ f = 1
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-/
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#guard_msgs in
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example : f = 1 := by apply rfl
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/-! Theorems should be exported without their bodies -/
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/--
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info: theorem t : f = 1 :=
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<not imported>
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-/
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#guard_msgs in
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#print t
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/--
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info: theorem trfl : f = 1 :=
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<not imported>
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-/
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#guard_msgs in
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#print trfl
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/-! Metadata of private decls should not be exported. -/
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-- Should not fail with 'unknown constant `inst*`
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/--
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error: failed to synthesize instance of type class
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X
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Hint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command.
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-/
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#guard_msgs in
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def fX : X := inferInstance
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/-- error: `dsimp` made no progress -/
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#guard_msgs in
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example : P f := by dsimp only [t]; exact hP1
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example : P f := by simp only [t]; exact hP1
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/-- error: `dsimp` made no progress -/
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#guard_msgs in
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example : P f := by dsimp only [trfl]; exact hP1
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/-- error: `dsimp` made no progress -/
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#guard_msgs in
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example : P f := by dsimp only [trfl']; exact hP1
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example : P fexp := by dsimp only [fexp_trfl]; exact hP1
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example : P fexp := by dsimp only [fexp_trfl']; exact hP1
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example : t = t := by dsimp only [trfl]
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/--
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error: Invalid field `eq_def`: The environment does not contain `Nat.eq_def`
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f
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has type
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Nat
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-/
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#guard_msgs in
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#check f.eq_def
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/--
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error: Invalid field `eq_unfold`: The environment does not contain `Nat.eq_unfold`
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f
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has type
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Nat
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-/
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#guard_msgs in
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#check f.eq_unfold
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/-- error: Unknown constant `f_struct.eq_1` -/
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#guard_msgs in
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#check f_struct.eq_1
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/-- error: Unknown constant `f_struct.eq_def` -/
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#guard_msgs in
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#check f_struct.eq_def
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/-- error: Unknown constant `f_struct.eq_unfold` -/
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#guard_msgs in
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#check f_struct.eq_unfold
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/-- error: Unknown constant `f_wfrec.eq_1` -/
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#guard_msgs in
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#check f_wfrec.eq_1
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/-- error: Unknown constant `f_wfrec.eq_def` -/
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#guard_msgs in
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#check f_wfrec.eq_def
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/-- error: Unknown constant `f_wfrec.eq_unfold` -/
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#guard_msgs in
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#check f_wfrec.eq_unfold
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/-- error: Unknown constant `f_wfrec.induct_unfolding` -/
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#guard_msgs(pass trace, all) in
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#check f_wfrec.induct_unfolding
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/-- info: f_exp_wfrec.eq_1 (x✝ : Nat) : f_exp_wfrec 0 x✝ = x✝ -/
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#guard_msgs in
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#check f_exp_wfrec.eq_1
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/--
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info: f_exp_wfrec.eq_def (x✝ x✝¹ : Nat) :
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f_exp_wfrec x✝ x✝¹ =
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match x✝, x✝¹ with
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| 0, acc => acc
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| n.succ, acc => f_exp_wfrec n (acc + 1)
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-/
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#guard_msgs in
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#check f_exp_wfrec.eq_def
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/--
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info: f_exp_wfrec.eq_unfold :
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f_exp_wfrec = fun x x_1 =>
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match x, x_1 with
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| 0, acc => acc
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| n.succ, acc => f_exp_wfrec n (acc + 1)
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-/
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#guard_msgs in
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#check f_exp_wfrec.eq_unfold
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/--
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info: f_exp_wfrec.induct_unfolding (motive : Nat → Nat → Nat → Prop) (case1 : ∀ (acc : Nat), motive 0 acc acc)
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(case2 : ∀ (n acc : Nat), motive n (acc + 1) (f_exp_wfrec n (acc + 1)) → motive n.succ acc (f_exp_wfrec n (acc + 1)))
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(a✝ a✝¹ : Nat) : motive a✝ a✝¹ (f_exp_wfrec a✝ a✝¹)
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-/
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#guard_msgs(pass trace, all) in
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#check f_exp_wfrec.induct_unfolding
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/-! Basic non-`meta` check. -/
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/-- error: Invalid definition `nonMeta`, may not access declaration `pubMeta` marked as `meta` -/
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#guard_msgs in
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def nonMeta := pubMeta
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/-! `simp` should not pick up inaccessible definitional equations. -/
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/-- error: `simp` made no progress -/
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#guard_msgs in
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theorem f_struct_eq : f_struct 0 = 0 := by
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simp
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/-! `[inherit_doc]` should work independently of visibility. -/
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/-- info: some "A private definition. " -/
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#guard_msgs in
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open Lean in
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#eval show CoreM _ from do findDocString? (← getEnv) ``pubInheritDoc
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/-! Cross-module `meta` checks, including involving compiler-introduced constants. -/
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attribute [local delab Nat] delab
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/--
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error: Cannot add attribute `[Lean.PrettyPrinter.Delaborator.delabAttribute]`: Declaration `noMetaDelab` must be marked as `meta`
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-/
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#guard_msgs in
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attribute [local delab Nat] noMetaDelab
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@[noinline] meta def pap (f : α → β) (a : α) : β := f a
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public meta def delab' : Lean.PrettyPrinter.Delaborator.Delab :=
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pap delab
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-- Used to complain about `_boxed` not being meta
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attribute [local delab Nat] delab'
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/--
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error: Invalid `meta` definition `metaUsingNonMeta`, `f` is not accessible here; consider adding `public meta import Module.Basic`
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-/
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#guard_msgs in
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public meta def metaUsingNonMeta : Nat :=
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f
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