averello/swift-mirror
1
0
Fork 0
mirror of https://github.com/apple/swift.git synced 2025-12-14 20:36:38 +01:00
Code Issues Packages Projects Releases Wiki Activity

Prevent non-ephemeral fix from affecting overload resolution

Browse Source 
This commit changes the behaviour of the error for
passing a temporary pointer conversion to an
@_nonEphemeral parameter such that it doesn't
affect overload resolution. This is done by recording
the fix with an impact of zero, meaning that we don't
touch the solution's score.

In addition, this change means we no longer need
to perform the ranking hack where we favour
array-to-pointer, as the disjunction short-circuiting
will continue to happen even with the fix recorded.
This commit is contained in:
Hamish Knight
2019-10-31 09:39:28 -07:00
parent 8cccbe0118
commit e7fe2a7a48
6 changed files with 35 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
lib/Sema/CSSimplify.cpp
View File

@@ -7933,14 +7933,15 @@ bool ConstraintSystem::recordFix(ConstraintFix *fix, unsigned impact) {
// Record the fix.
// If this is just a warning it's shouldn't affect the solver.
if (!fix->isWarning()) {
// Otherswise increase the score. If this would make the current
// solution worse than the best solution we've seen already, stop now.
// If this is just a warning, it shouldn't affect the solver. Otherwise,
// increase the score.
if (!fix->isWarning())
increaseScore(SK_Fix, impact);
if (worseThanBestSolution())
return true;
}
// If we've made the current solution worse than the best solution we've seen
// already, stop now.
if (worseThanBestSolution())
return true;
if (isAugmentingFix(fix)) {
// Always useful, unless duplicate of exactly the same fix and location.
@@ -8084,30 +8085,13 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
// note of the fix.
auto conversion = theFix->getConversionKind();
switch (isConversionEphemeral(conversion, locator)) {
case ConversionEphemeralness::Ephemeral: {
if (recordFix(fix))
case ConversionEphemeralness::Ephemeral:
// Record the fix with an impact of zero. This ensures that non-ephemeral
// diagnostics don't impact solver behavior.
if (recordFix(fix, /*impact*/ 0))
return SolutionKind::Error;
// FIXME: Currently, as a performance hack, we short-circuit disjunctions
// such that we favour array-to-pointer conversions over inout-to-pointer
// conversions. However we don't do this when fixes are involved.
// Therefore in order to improve diagnostics for cases where both
// array-to-pointer and inout-to-pointer are viable with fixes, increase
// the score of inout-to-pointer by 1. This means we'll complain about
// the use of array-to-pointer, which is more likely to be what the user
// was trying to do.
//
// Ideally, we would either have a proper ranking rule that favors
// array-to-pointer over inout-to-pointer (not just within a disjunction),
// or we would have some logic to merge solutions with fixes that would
// be better diagnosed by a single fix rather than an ambiguity error
// with notes from fixes.
if (!theFix->isWarning() &&
conversion == ConversionRestrictionKind::InoutToPointer)
increaseScore(SK_ValueToPointerConversion);
return SolutionKind::Solved;
}
case ConversionEphemeralness::NonEphemeral:
return SolutionKind::Solved;
case ConversionEphemeralness::Unresolved: