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[CSDiag] Start chipping away at FailureDiagnosis::diagnoseAmbiguity #29415

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Merged
merged 2 commits into from
Jan 24, 2020
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[CSDiag] Start chipping away at FailureDiagnosis::diagnoseAmbiguity #29415

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74f65ba
[ConstraintSystem] Find solutions for code with invalid '_' using
hborla Jan 23, 2020
689a57b
[CSDiag] Remove some dead code for diagnosing ambiguity from CSDiag.
hborla Jan 24, 2020
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99 changes: 0 additions & 99 deletions lib/Sema/CSDiag.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1447,29 +1447,6 @@ bool FailureDiagnosis::visitApplyExpr(ApplyExpr *callExpr) {
auto lhsType = CS.getType(lhsExpr)->getRValueType();
auto rhsType = CS.getType(rhsExpr)->getRValueType();

// TODO(diagnostics): There are still cases not yet handled by new
// diagnostics framework e.g.
//
// var tuple = (1, 2, 3)
// switch tuple {
// case (let (_, _, _)) + 1: break
// }
if (callExpr->isImplicit() && overloadName == "~=") {
auto flags = ParameterTypeFlags();
if (calleeInfo.candidates.size() == 1)
if (auto fnType = calleeInfo.candidates[0].getFunctionType())
flags = fnType->getParams()[0].getParameterFlags();

auto *locator = CS.getConstraintLocator(
callExpr,
{ConstraintLocator::ApplyArgument,
LocatorPathElt::ApplyArgToParam(0, 0, flags)},
/*summaryFlags=*/0);

ArgumentMismatchFailure failure(CS, lhsType, rhsType, locator);
return failure.diagnosePatternMatchingMismatch();
}

if (isContextualConversionFailure(argTuple))
return false;

Expand Down Expand Up @@ -1517,41 +1494,6 @@ bool FailureDiagnosis::visitApplyExpr(ApplyExpr *callExpr) {
AnyFunctionType::decomposeInput(CS.getType(argExpr), params);
auto argString = AnyFunctionType::getParamListAsString(params);

// If we couldn't get the name of the callee, then it must be something of a
// more complex "value of function type".
if (overloadName.empty()) {
// If we couldn't infer the result type of the closure expr, then we have
// some sort of ambiguity, let the ambiguity diagnostic stuff handle this.
if (auto ffty = fnType->getAs<AnyFunctionType>())
if (ffty->getResult()->hasTypeVariable()) {
diagnoseAmbiguity(fnExpr);
return true;
}

// The most common unnamed value of closure type is a ClosureExpr, so
// special case it.
if (isa<ClosureExpr>(fnExpr->getValueProvidingExpr())) {
if (fnType->hasTypeVariable())
diagnose(argExpr->getStartLoc(), diag::cannot_invoke_closure, argString)
.highlight(fnExpr->getSourceRange());
else
diagnose(argExpr->getStartLoc(), diag::cannot_invoke_closure_type,
fnType, argString)
.highlight(fnExpr->getSourceRange());

} else if (fnType->hasTypeVariable()) {
diagnose(argExpr->getStartLoc(), diag::cannot_call_function_value,
argString)
.highlight(fnExpr->getSourceRange());
} else {
diagnose(argExpr->getStartLoc(), diag::cannot_call_value_of_function_type,
fnType, argString)
.highlight(fnExpr->getSourceRange());
}

return true;
}

if (auto MTT = fnType->getAs<MetatypeType>()) {
if (MTT->getInstanceType()->isExistentialType()) {
diagnose(fnExpr->getLoc(), diag::construct_protocol_value, fnType);
Expand Down Expand Up @@ -1754,22 +1696,6 @@ void FailureDiagnosis::diagnoseAmbiguity(Expr *E) {
if (auto *assignment = dyn_cast<AssignExpr>(E)) {
if (isa<DiscardAssignmentExpr>(assignment->getDest())) {
auto *srcExpr = assignment->getSrc();

bool diagnosedInvalidUseOfDiscardExpr = false;
srcExpr->forEachChildExpr([&](Expr *expr) -> Expr * {
if (auto *DAE = dyn_cast<DiscardAssignmentExpr>(expr)) {
diagnose(DAE->getLoc(), diag::discard_expr_outside_of_assignment)
.highlight(srcExpr->getSourceRange());
diagnosedInvalidUseOfDiscardExpr = true;
return nullptr;
}

return expr;
});

if (diagnosedInvalidUseOfDiscardExpr)
return;

diagnoseAmbiguity(srcExpr);
return;
}
Expand All @@ -1783,15 +1709,6 @@ void FailureDiagnosis::diagnoseAmbiguity(Expr *E) {
return;
}

// A DiscardAssignmentExpr (spelled "_") needs contextual type information to
// infer its type. If we see one at top level, diagnose that it must be part
// of an assignment so we don't get a generic "expression is ambiguous" error.
if (isa<DiscardAssignmentExpr>(E)) {
diagnose(E->getLoc(), diag::discard_expr_outside_of_assignment)
.highlight(E->getSourceRange());
return;
}

// Diagnose ".foo" expressions that lack context specifically.
if (auto UME =
dyn_cast<UnresolvedMemberExpr>(E->getSemanticsProvidingExpr())) {
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Btw, I think this should be obsolete as well because diagnostics for _ = .foo have been ported already as missing base type for unresolved member.

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@hborla hborla Jan 24, 2020 •
edited
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It isn't yet :/ it's still handling cases like this, where the solver does find multiple solutions with fixes but it isn't yet diagnosed in diagnoseAmbiguityWithFixes :

func f(_: Int) {}
func f(_: String) {}

f(.nothing)

I'm currently working on this case though!

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Ah, that comment on top threw me off :)

Expand All @@ -1803,22 +1720,6 @@ void FailureDiagnosis::diagnoseAmbiguity(Expr *E) {
}
}

// Diagnose empty collection literals that lack context specifically.
if (auto CE = dyn_cast<CollectionExpr>(E->getSemanticsProvidingExpr())) {
if (CE->getNumElements() == 0) {
diagnose(E->getLoc(), diag::unresolved_collection_literal)
.highlight(E->getSourceRange());
return;
}
}

// Diagnose 'nil' without a contextual type.
if (isa<NilLiteralExpr>(E->getSemanticsProvidingExpr())) {
diagnose(E->getLoc(), diag::unresolved_nil_literal)
.highlight(E->getSourceRange());
return;
}

// Attempt to re-type-check the entire expression, allowing ambiguity, but
// ignoring a contextual type.
if (expr == E) {
Expand Down
3 changes: 2 additions & 1 deletion lib/Sema/CSGen.cpp
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Expand Up @@ -2827,7 +2827,8 @@ namespace {

Type visitDiscardAssignmentExpr(DiscardAssignmentExpr *expr) {
auto locator = CS.getConstraintLocator(expr);
auto typeVar = CS.createTypeVariable(locator, TVO_CanBindToNoEscape);
auto typeVar = CS.createTypeVariable(locator, TVO_CanBindToNoEscape |
TVO_CanBindToHole);
return LValueType::get(typeVar);
}

Expand Down
2 changes: 1 addition & 1 deletion test/Constraints/diagnostics.swift
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Expand Up @@ -1271,7 +1271,7 @@ func badTypes() {
// rdar://34357545
func unresolvedTypeExistential() -> Bool {
return (Int.self==_{})
// expected-error@-1 {{expression type 'Bool' is ambiguous without more context}}
// expected-error@-1 {{'_' can only appear in a pattern or on the left side of an assignment}}
}

func rdar43525641(_ a: Int, _ b: Int = 0, c: Int = 0, _ d: Int) {}
Expand Down
3 changes: 1 addition & 2 deletions test/Parse/matching_patterns.swift
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Expand Up @@ -288,8 +288,7 @@ case (_, var e, 3) +++ (1, 2, 3):
// expected-error@-2{{'var' binding pattern cannot appear in an expression}}
()
case (let (_, _, _)) + 1:
// expected-error@-1 2 {{'var' binding pattern cannot appear in an expression}}
// expected-error@-2 {{expression pattern of type 'Int' cannot match values of type '(Int, Int, Int)'}}
// expected-error@-1 {{expression pattern of type 'Int' cannot match values of type '(Int, Int, Int)'}}
()
}

Expand Down
2 changes: 1 addition & 1 deletion test/expr/expressions.swift
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Expand Up @@ -708,7 +708,7 @@ func test() {
func unusedExpressionResults() {
// Unused l-value
_ // expected-error{{'_' can only appear in a pattern or on the left side of an assignment}}

// expected-error@-1 {{expression resolves to an unused variable}}

// <rdar://problem/20749592> Conditional Optional binding hides compiler error
let optionalc:C? = nil
Expand Down