a1240f7b80
This PR fixes the `ControlInfo` inference for a do-block `match`: the
fold over the match arms started from `ControlInfo.pure` (defaults to
`numRegularExits := 1`, `noFallthrough := false`), but `alternative`
sums `numRegularExits` and ANDs `noFallthrough`, so the fold identity is
`{ numRegularExits := 0, noFallthrough := true }`. With the wrong base,
a `match` whose arms all `break`/`continue`/`return` reported
`numRegularExits = 1` and `noFallthrough = false`, suppressing the
dead-code warning on the continuation after the match. The fix corrects
both the inference handler in `InferControlInfo.lean` and the fold in
`elabDoMatchCore`.
82 lines
2.3 KiB
Text
82 lines
2.3 KiB
Text
set_option backward.do.legacy false
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-- When an inner doElem's `ControlInfo` has `numRegularExits := 0` (because all branches
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-- `break`/`continue`/`return`, or it is a non-terminating `repeat`), the trailing `return`
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-- inside the enclosing `for` body used to be dropped during inference, and the for elaborator
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-- then threw "Early returning ... but the info said there is no early return" even though the
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-- elaborator does visit the trailing element. `ofSeq`/`ControlInfo.sequence` now aggregate
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-- `breaks`/`continues`/`returnsEarly`/`reassigns` past `numRegularExits == 0` elements, so the
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-- inferred info matches what the elaborator actually sees.
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/--
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warning: This `do` element and its control-flow region are dead code. Consider refactoring your code to remove it.
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-/
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#guard_msgs in
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example (cond : Bool) : IO Nat := do
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for _ in [1, 2] do
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if cond then break else break
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return 42
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return 1
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/--
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warning: This `do` element and its control-flow region are dead code. Consider refactoring your code to remove it.
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-/
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#guard_msgs in
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example (cond : Bool) : IO Nat := do
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for _ in [1, 2] do
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if cond then continue else continue
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return 42
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return 1
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/--
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warning: This `do` element and its control-flow region are dead code. Consider refactoring your code to remove it.
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-/
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#guard_msgs in
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example (i : Nat) : IO Nat := do
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for _ in [1, 2] do
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match i with
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| 0 => break
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| _ => break
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return 42
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return 1
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/--
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warning: This `do` element and its control-flow region are dead code. Consider refactoring your code to remove it.
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-/
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#guard_msgs in
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example : IO Nat := do
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for _ in [1, 2] do
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try break catch _ => break
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return 42
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return 1
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/--
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warning: This `do` element and its control-flow region are dead code. Consider refactoring your code to remove it.
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-/
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#guard_msgs in
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example (cond : Bool) : IO Nat := do
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for _ in [1, 2] do
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unless cond do break
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if cond then break else break
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return 42
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return 1
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#guard_msgs in
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example : IO Nat := do
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for _ in [1, 2] do
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repeat
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pure ()
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return 42
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return 1
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-- The `return 2` is required to give the do block its `Id Nat` result type; no dead-code warning
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-- should fire on it.
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#guard_msgs in
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example (x : Nat) : Id Nat := do
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if x = 3 then
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repeat
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pure ()
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else
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repeat
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pure ()
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return 2
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