0684c95d35
Now, only `(<- ...)`s occurring in the condition of a pure if-then-else are lifted. That is, `if (<- foo) then ... else ...` is ok, but `if ... then (<- foo) else ...` is not. See #3713 closes #3713 This PR also adjusts this repo. Note that some of the `(<- ...)` were harmless since they were just accessing some read-only state.
35 lines
626 B
Text
35 lines
626 B
Text
import Lean
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open Lean Elab Meta
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def somethingBad : MetaM Nat := do
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IO.println "oh no"
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return 1
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/--
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error: invalid use of `(<- ...)`, must be nested inside a 'do' expression
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---
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info:
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-/
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#guard_msgs in
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#eval show MetaM Unit from do
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let t := if false then ← somethingBad else 9
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def foo : MetaM Bool :=
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return false
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/--
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error: invalid use of `(<- ...)`, must be nested inside a 'do' expression
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---
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info:
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-/
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#guard_msgs in
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#eval show MetaM Unit from do
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let t := if (← foo) then ← somethingBad else 9
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/--
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info: 1
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-/
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#guard_msgs in
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#eval show MetaM Nat from do
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let t := if (← foo) then 0 else 1
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return t
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