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[SpaceEngine] Remove isUseful and don't include redundant spaces. #17805

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Merged
merged 2 commits into from
Jul 7, 2018
Merged

[SpaceEngine] Remove isUseful and don't include redundant spaces. #17805

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372fe24
[SpaceEngine] Don't include redundant cases into "covered" space
xedin Jul 6, 2018
840269b
[SpaceEngine] Remove `isUseful` due to eager empty sub-space pruning
xedin Jul 6, 2018
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38 changes: 4 additions & 34 deletions lib/Sema/TypeCheckSwitchStmt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -319,38 +319,6 @@ namespace {
return TypeAndVal.getInt();
}

// Defines a "usefulness" metric that returns whether the given space
// contributes meaningfully to the exhaustiveness of a pattern.
bool isUseful() const {
auto subspacesUseful = [](const Space &space) {
for (auto &subspace : space.getSpaces()) {
if (!subspace.isUseful()) {
return false;
}
}
return true;
};

switch (getKind()) {
case SpaceKind::Empty:
return false;
case SpaceKind::Type:
case SpaceKind::BooleanConstant:
case SpaceKind::UnknownCase:
return true;
case SpaceKind::Disjunct:
if (getSpaces().empty()) {
return false;
}
return subspacesUseful(*this);
case SpaceKind::Constructor:
if (getSpaces().empty()) {
return true;
}
return subspacesUseful(*this);
}
}

// An optimization that computes if the difference of this space and
// another space is empty.
bool isSubspace(const Space &other, TypeChecker &TC,
Expand Down Expand Up @@ -1178,13 +1146,14 @@ namespace {
Space projection = projectPattern(TC, caseItem.getPattern(),
sawDowngradablePattern);

if (projection.isUseful()
&& projection.isSubspace(Space::forDisjunct(spaces), TC, DC)) {
if (!projection.isEmpty() &&
projection.isSubspace(Space::forDisjunct(spaces), TC, DC)) {
sawRedundantPattern |= true;

TC.diagnose(caseItem.getStartLoc(),
diag::redundant_particular_case)
.highlight(caseItem.getSourceRange());
continue;
} else {
Expr *cachedExpr = nullptr;
if (checkRedundantLiteral(caseItem.getPattern(), cachedExpr)) {
Expand All @@ -1195,6 +1164,7 @@ namespace {
TC.diagnose(cachedExpr->getLoc(),
diag::redundant_particular_literal_case_here)
.highlight(cachedExpr->getSourceRange());
continue;
}
}
spaces.push_back(projection);
Expand Down