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Introduce then statements

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These allow multi-statement `if`/`switch` expression
branches that can produce a value at the end by
saying `then <expr>`. This is gated behind
`-enable-experimental-feature ThenStatements`
pending evolution discussion.
This commit is contained in:
Hamish Knight
2023-09-01 14:32:14 +01:00
parent 99a36b3f00
commit 6ee44f09b4
47 changed files with 1063 additions and 196 deletions
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22
lib/Sema/CSSimplify.cpp
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@@ -6370,7 +6370,7 @@ bool ConstraintSystem::repairFailures(
}
case ConstraintLocator::TernaryBranch:
case ConstraintLocator::SingleValueStmtBranch: {
case ConstraintLocator::SingleValueStmtResult: {
recordAnyTypeVarAsPotentialHole(lhs);
recordAnyTypeVarAsPotentialHole(rhs);
@@ -7813,16 +7813,20 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
// value statements.
//
// As with the previous checks, we only allow the Void conversion in
// an implicit single-expression closure. In the more general case, we
// only allow the Never conversion.
// an implicit single-expression closure. In the more general case for
// implicit branches, we only allow the Never conversion. For explicit
// branches, no conversions are allowed.
auto *loc = getConstraintLocator(locator);
if (auto branchKind = loc->isForSingleValueStmtBranch()) {
bool allowConversion = false;
switch (*branchKind) {
case SingleValueStmtBranchKind::Regular:
case SingleValueStmtBranchKind::Explicit:
allowConversion = false;
break;
case SingleValueStmtBranchKind::Implicit:
allowConversion = type1->isUninhabited();
break;
case SingleValueStmtBranchKind::InSingleExprClosure:
case SingleValueStmtBranchKind::ImplicitInSingleExprClosure:
allowConversion = true;
break;
}
@@ -15200,12 +15204,12 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
impact = 5;
}
}
using SingleValueStmtBranch = LocatorPathElt::SingleValueStmtBranch;
if (auto branchElt = locator->getLastElementAs<SingleValueStmtBranch>()) {
using SingleValueStmtResult = LocatorPathElt::SingleValueStmtResult;
if (auto branchElt = locator->getLastElementAs<SingleValueStmtResult>()) {
// Similar to a ternary, except we have N branches. Let's prefer the fix
// on the first branch, and discount subsequent branches by index.
if (branchElt->getExprBranchIndex() > 0)
impact = 9 + branchElt->getExprBranchIndex();
if (branchElt->getIndex() > 0)
impact = 9 + branchElt->getIndex();
}
// Increase impact of invalid conversions to `Any` and `AnyHashable`
// associated with collection elements (i.e. for-in sequence element)