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`.
38 lines
890 B
Text
38 lines
890 B
Text
import Lean.Meta
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open Lean
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open Lean.Meta
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def tst1 : MetaM Unit :=
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withLocalDeclD `y (mkConst `Nat) $ fun y => do
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withLetDecl `x (mkConst `Nat) (mkNatLit 0) $ fun x => do {
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let mvar ← mkFreshExprMVar (mkConst `Nat) MetavarKind.syntheticOpaque;
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trace[Meta.debug] mvar;
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let r ← mkLambdaFVars #[y, x] mvar;
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trace[Message.debug] r;
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let v := mkApp2 (mkConst `Nat.add) x y;
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mvar.mvarId!.assign v;
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trace[Meta.debug] mvar;
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trace[Meta.debug] r;
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let mctx ← getMCtx;
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mctx.decls.forM fun mvarId mvarDecl => do
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trace[Meta.debug] m!"?{mvarId.name} : {mvarDecl.type}"
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}
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set_option pp.mvars false
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set_option trace.Meta.debug true
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/--
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info: [Meta.debug] ?_
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[Meta.debug] x.add y
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[Meta.debug] fun y =>
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let x := 0;
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x.add y
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[Meta.debug] ?_uniq.3014 : Nat
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[Meta.debug] ?_uniq.3015 : Nat →
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Nat →
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let x := 0;
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Nat
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-/
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#guard_msgs in
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#eval tst1
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