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Fix Issue 19213 - goto skips declaration of variable in std.algorithm… #6803

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merged 1 commit into from
Dec 31, 2018
Merged

Fix Issue 19213 - goto skips declaration of variable in std.algorithm… #6803

merged 1 commit into from
Dec 31, 2018

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edi33416
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….iteration.joiner

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dlang-bot commented Dec 12, 2018 •
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Thanks for your pull request and interest in making D better, @edi33416! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
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Bugzilla references

Auto-close Bugzilla Severity Description
✓ 19213 regression goto skips declaration of variable in std.algorithm.iteration.joiner

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Changes to popBackEmptyElements were made to be consistent with the changes required by popFrontEmptyElements.

Note: the regression can be fixed just with the changes done in popFrontEmptyElements

wilzbach
wilzbach previously requested changes Dec 12, 2018
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Needs a test

wilzbach
wilzbach reviewed Dec 12, 2018
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std/algorithm/iteration.d
// we need to .save each subrange we traverse.
static if (isForwardRange!RoR && isForwardRange!(ElementType!RoR))
_current = _items.front.save;
if (!_items.empty)
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This is sub-optimal as it will be executed one-more time than strictly necessary.

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It should be faster to do sth. this:

while (!_items.empty) {
   if (!_items.front.empty) {
      _items.popFront();
   } else {
     // <- static if code here
     break;
   }
}

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I still need the outside if (!_items.empty) { } else { } block, or the compiler will complain with Error: one path skips field _current.

This is because, in the case of an empty ROR, _current won't be initialised.

std/algorithm/iteration.d
end:
assert(1); // required to avoid 'EOF instead of statement' error
{
_current = typeof(_current).init;
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Why is this required?

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The compiler requires that _current is initialised on all possible paths.

std/algorithm/iteration.d
else
_currentBack = _items.back;
_current = typeof(_current).init;
_currentBack = typeof(_currentBack).init;
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Why is this required?

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Please see above comments

std/algorithm/iteration.d
// consumed when a .save'd copy of ourselves is iterated over. So
// we need to .save each subrange we traverse.
static if (isForwardRange!RoR && isForwardRange!(ElementType!RoR))
if (!_items.empty)
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This is sub-optimal as it will be executed one-more time than strictly necessary.

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Please see above comments

@edi33416 edi33416 force-pushed the issue_19213 branch 2 times, most recently from 48e2215 to 17b7366 Compare December 14, 2018 13:08
@edi33416 edi33416 changed the base branch from master to stable December 14, 2018 13:09
wilzbach
wilzbach reviewed Dec 18, 2018
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std/algorithm/iteration.d Outdated
auto results = [[1,2], [3,4]]
.map!(q => q.map!Rec.chunkBy!"a.foo")
.joiner;
}));
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No need to use __traits(compiles here. Use the range directly and even assert that its still iterated correctly.
Also, it would be good to add a test for iterating this range backwards and checking the result.

std/algorithm/iteration.d Outdated
@@ -2948,6 +2955,20 @@ if (isInputRange!RoR && isInputRange!(ElementType!RoR))
assert(!equal(js2, js));
}

// Bugzilla issue 19213
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Use links to Bugzilla.

wilzbach
wilzbach reviewed Dec 20, 2018
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std/algorithm/iteration.d Outdated
{
auto results = [[1,2], [3,4]].map!(q => q.chunkBy!"a").joiner;
int i = 1;
foreach(ref e; results)
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Style target fails here due to missing whitespace after foreach. Why not use equals?
Also, we should probably test the bidirectional code too (use e.g. retro)

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The result is not a bidirectional range, so I can't use retro.

@wilzbach wilzbach dismissed their stale review December 31, 2018 11:52

ok let's at least fix the bug before 2.084

@wilzbach wilzbach merged commit 07ea0e0 into dlang:stable Dec 31, 2018
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@wilzbach wilzbach wilzbach approved these changes

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@edi33416 @dlang-bot @wilzbach