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`.
52 lines
1.4 KiB
Text
52 lines
1.4 KiB
Text
@[inline] def f {α} (s : String) (x : IO α) : IO α := do
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IO.println "started";
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IO.println s;
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let a ← x;
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IO.println ("ended");
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pure a
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@[inline] def f'' {α m} [MonadControlT IO m] [Monad m] (msg : String) (x : m α) : m α := do
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controlAt IO fun runInBase => f msg (runInBase x)
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abbrev M := StateT Bool $ ExceptT String $ StateT String $ ReaderT Nat $ StateT Nat IO
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def tst : M Nat := do
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let a ← f'' "hello" do {
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let s ← getThe Nat; let ctx ← read; modifyThe Nat fun s => s + ctx; if s > 10 then { throw "ERROR" }; getThe Nat };
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modifyThe Nat Nat.succ;
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pure a
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/--
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info: started
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hello
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ended
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---
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info: ((Except.error "ERROR", "world"), 1011)
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-/
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#guard_msgs in
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#eval (((tst.run true).run "world").run 1000).run 11
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@[inline] def g {α} (s : String) (x : Nat → IO α) : IO α := do
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IO.println "started";
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IO.println s;
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let a ← x s.length;
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IO.println ("ended");
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pure a
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@[inline] def g' {α m} [MonadControlT IO m] [Monad m] (msg : String) (x : Nat → m α) : m α := do
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controlAt IO fun runInBase => g msg (fun n => runInBase (x n))
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def tst2 : M Nat := do
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let a ← g' "hello" fun x => do { let s ← getThe Nat; let ctx ← read; modifyThe Nat fun s => s + ctx + x; if s > 10 then { throw "ERROR" }; getThe Nat };
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modifyThe Nat Nat.succ;
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pure a
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/--
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info: started
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hello
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ended
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---
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info: ((Except.ok (1015, true), "world"), 1016)
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-/
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#guard_msgs in
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#eval (((tst2.run true).run "world").run 1000).run 10
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