fdd5aec172
This refactors and improves the `#eval` command, introducing some new
features.
* Now evaluated results can be represented using `ToExpr` and pretty
printing. This means **hoverable output**. If `ToExpr` fails, it then
tries `Repr` and then `ToString`. The `eval.pp` option controls whether
or not to try `ToExpr`.
* There is now **auto-derivation** of `Repr` instances, enabled with the
`pp.derive.repr` option (default to **true**). For example:
```lean
inductive Baz
| a | b
#eval Baz.a
-- Baz.a
```
It simply does `deriving instance Repr for Baz` when there's no way to
represent `Baz`. If core Lean gets `ToExpr` derive handlers, they could
be used here as well.
* The option `eval.type` controls whether or not to include the type in
the output. For now the default is false.
* Now things like `#eval do return 2` work. It tries using
`CommandElabM`, `TermElabM`, or `IO` when the monad is unknown.
* Now there is no longer `Lean.Eval` or `Lean.MetaEval`. These each used
to be responsible for both adapting monads and printing results. The
concerns have been split into two. (1) The `MonadEval` class is
responsible for adapting monads for evaluation (it is similar to
`MonadLift`, but instances are allowed to use default data when
initializing state) and (2) finding a way to represent results is
handled separately.
* Error messages about failed instance synthesis are now more precise.
Once it detects that a `MonadEval` class applies, then the error message
will be specific about missing `ToExpr`/`Repr`/`ToString` instances.
* Fixes a bug where `Repr`/`ToString` instances can't be found by
unfolding types "under the monad". For example, this works now:
```lean
def Foo := List Nat
def Foo.mk (l : List Nat) : Foo := l
#eval show Lean.CoreM Foo from do return Foo.mk [1,2,3]
```
* Elaboration errors now abort evaluation. This eliminates some
not-so-relevant error messages.
* Now evaluating a value of type `m Unit` never prints a blank message.
* Fixes bugs where evaluating `MetaM` and `CoreM` wouldn't collect log
messages.
The `run_cmd`, `run_elab`, and `run_meta` commands are now frontends for
`#eval`.
123 lines
2.5 KiB
Text
123 lines
2.5 KiB
Text
def checkM (b : IO Bool) : IO Unit :=
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unless (← b) do throw $ IO.userError "failed"
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abbrev M := ExceptT String $ StateRefT Nat IO
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def f1 : M Nat :=
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throw "error 1"
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def f2 : M Nat :=
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throwThe IO.Error $ IO.userError "error 2"
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def tst1 : M Nat := do
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try
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try f1 finally set 100; IO.println "finisher executed"
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catch _ =>
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get
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def checkE {α ε : Type} [BEq α] (x : IO (Except ε α)) (expected : α) : IO Unit := do
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let r ← x;
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match r with
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| Except.ok a => unless a == expected do throw $ IO.userError "unexpected result"
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| Except.error _ => throw $ IO.userError "unexpected error"
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/--
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info: finisher executed
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---
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info: Except.ok 100
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-/
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#guard_msgs in
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#eval (tst1.run).run' 0
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/-- info: finisher executed -/
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#guard_msgs in
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#eval checkE ((tst1.run).run' 0) 100
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def tst2 : M Nat :=
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tryCatchThe IO.Error
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(tryFinally f2 (do set 100; IO.println "finisher executed"))
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(fun _ => get)
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/--
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info: finisher executed
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---
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info: Except.ok 100
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-/
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#guard_msgs in
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#eval (tst2.run).run' 0
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/-- info: finisher executed -/
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#guard_msgs in
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#eval checkE ((tst2.run).run' 0) 100
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def tst3 : M Nat :=
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tryCatchThe IO.Error
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(tryFinally
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(tryFinally f1 (do set 100; IO.println "inner finisher executed"; discard $ f2; pure ()))
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(do modify Nat.succ; IO.println "outer finisher executed"))
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(fun _ => get)
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/--
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info: inner finisher executed
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outer finisher executed
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---
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info: Except.ok 101
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-/
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#guard_msgs in
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#eval (tst3.run).run' 0
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/--
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info: inner finisher executed
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outer finisher executed
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-/
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#guard_msgs in
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#eval checkE ((tst3.run).run' 0) 101
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def tst4 : M Nat := do
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let a ← tryFinally
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(tryFinally (pure 42) (do set 100; IO.println "inner finisher executed"; pure ()))
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(do modify Nat.succ; IO.println "outer finisher executed");
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let s ← get;
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pure (a + s)
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/--
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info: inner finisher executed
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outer finisher executed
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---
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info: Except.ok 143
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-/
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#guard_msgs in
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#eval (tst4.run).run' 0
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/--
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info: inner finisher executed
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outer finisher executed
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-/
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#guard_msgs in
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#eval checkE ((tst4.run).run' 0) 143
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def tst5 : M Nat := do
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let (a, _) ← tryFinally' (pure 42) (fun a? => do IO.println ("finalizer received: " ++ toString a?));
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pure a
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/--
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info: finalizer received: (some 42)
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---
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info: Except.ok 42
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-/
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#guard_msgs in
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#eval (tst5.run).run' 0
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def tst6 : M Nat := do
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let (a, _) ← tryFinally' f2 (fun a? => do IO.println ("finalizer received: " ++ toString a?));
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pure a
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def tst7 : IO Unit :=
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tryCatchThe IO.Error (do discard $ (tst6.run).run' 0; pure ()) (fun _ => IO.println "failed as expected")
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/--
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info: finalizer received: none
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failed as expected
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-/
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#guard_msgs in
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#eval tst7
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