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[5.1][ConstraintSystem] Detect and diagnose missing generic arguments #25485

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Jun 15, 2019
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[5.1][ConstraintSystem] Detect and diagnose missing generic arguments #25485

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2 changes: 2 additions & 0 deletions include/swift/AST/DiagnosticsSema.def
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Original file line number Diff line number Diff line change
Expand Up @@ -928,6 +928,8 @@ NOTE(note_call_to_operator,none,
"in call to operator %0", (DeclName))
NOTE(note_call_to_func,none,
"in call to function %0", (DeclName))
NOTE(note_call_to_subscript,none,
"in call to %0", (DeclName))
NOTE(note_call_to_initializer,none,
"in call to initializer", ())
NOTE(note_init_parameter,none,
Expand Down
4 changes: 4 additions & 0 deletions include/swift/AST/TypeRepr.h
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Expand Up @@ -363,6 +363,10 @@ class GenericIdentTypeRepr final : public ComponentIdentTypeRepr,
ArrayRef<TypeRepr*> GenericArgs,
SourceRange AngleBrackets);

unsigned getNumGenericArgs() const {
return Bits.GenericIdentTypeRepr.NumGenericArgs;
}

ArrayRef<TypeRepr*> getGenericArgs() const {
return {getTrailingObjects<TypeRepr*>(),
Bits.GenericIdentTypeRepr.NumGenericArgs};
Expand Down
187 changes: 6 additions & 181 deletions lib/Sema/CSDiag.cpp
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Expand Up @@ -7083,125 +7083,6 @@ void ConstraintSystem::diagnoseFailureForExpr(Expr *expr) {
diagnosis.diagnoseAmbiguity(expr);
}

static bool hasGenericParameter(const GenericTypeDecl *generic,
GenericTypeParamType *paramTy) {
auto *decl = paramTy->getDecl();
if (!decl)
return false;

return decl->getDeclContext() == generic;
}

static void noteGenericParameterSource(const TypeLoc &loc,
GenericTypeParamType *paramTy,
ConstraintSystem &cs) {
const GenericTypeDecl *FoundDecl = nullptr;
const ComponentIdentTypeRepr *FoundGenericTypeBase = nullptr;

// Walk the TypeRepr to find the type in question.
if (auto typerepr = loc.getTypeRepr()) {
struct FindGenericTypeDecl : public ASTWalker {
const GenericTypeDecl *FoundDecl = nullptr;
const ComponentIdentTypeRepr *FoundGenericTypeBase = nullptr;
GenericTypeParamType *ParamTy;

FindGenericTypeDecl(GenericTypeParamType *ParamTy)
: ParamTy(ParamTy) {}

bool walkToTypeReprPre(TypeRepr *T) override {
// If we already emitted the note, we're done.
if (FoundDecl) return false;

if (auto ident = dyn_cast<ComponentIdentTypeRepr>(T)) {
auto *generic =
dyn_cast_or_null<GenericTypeDecl>(ident->getBoundDecl());
if (generic && hasGenericParameter(generic, ParamTy)) {
FoundDecl = generic;
FoundGenericTypeBase = ident;
return false;
}
}
// Keep walking.
return true;
}
} findGenericTypeDecl(paramTy);

typerepr->walk(findGenericTypeDecl);
FoundDecl = findGenericTypeDecl.FoundDecl;
FoundGenericTypeBase = findGenericTypeDecl.FoundGenericTypeBase;
}

// If we didn't find the type in the TypeRepr, fall back to the type in the
// type checked expression.
if (!FoundDecl) {
if (const GenericTypeDecl *generic = loc.getType()->getAnyGeneric())
if (hasGenericParameter(generic, paramTy))
FoundDecl = generic;
}

auto &tc = cs.getTypeChecker();
if (FoundDecl) {
Type type;
if (auto *nominal = dyn_cast<NominalTypeDecl>(FoundDecl))
type = nominal->getDeclaredType();
else if (auto *typeAlias = dyn_cast<TypeAliasDecl>(FoundDecl))
type = typeAlias->getUnboundGenericType();
else
type = FoundDecl->getDeclaredInterfaceType();
tc.diagnose(FoundDecl, diag::archetype_declared_in_type, paramTy, type);
}

if (FoundGenericTypeBase && !isa<GenericIdentTypeRepr>(FoundGenericTypeBase)){
assert(FoundDecl);

// If we can, prefer using any types already fixed by the constraint system.
// This lets us produce fixes like `Pair<Int, Any>` instead of defaulting to
// `Pair<Any, Any>`.
// Right now we only handle this when the type that's at fault is the
// top-level type passed to this function.
auto type = loc.getType();
if (!type)
type = cs.getType(loc);

ArrayRef<Type> genericArgs;

if (auto *boundGenericTy = type->getAs<BoundGenericType>()) {
if (boundGenericTy->getDecl() == FoundDecl)
genericArgs = boundGenericTy->getGenericArgs();
}

auto getPreferredType =
[&](const GenericTypeParamDecl *genericParam) -> Type {
// If we were able to get the generic arguments (i.e. the types used at
// FoundDecl's use site), we can prefer those...
if (genericArgs.empty())
return Type();

Type preferred = genericArgs[genericParam->getIndex()];
if (!preferred || preferred->hasError())
return Type();

// ...but only if they were actually resolved by the constraint system
// despite the failure.
Type maybeFixedType = cs.getFixedTypeRecursive(preferred,
/*wantRValue*/true);
if (maybeFixedType->hasTypeVariable() ||
maybeFixedType->hasUnresolvedType()) {
return Type();
}
return maybeFixedType;
};

SmallString<64> genericParamBuf;
if (tc.getDefaultGenericArgumentsString(genericParamBuf, FoundDecl,
getPreferredType)) {
tc.diagnose(FoundGenericTypeBase->getLoc(),
diag::unbound_generic_parameter_explicit_fix)
.fixItInsertAfter(FoundGenericTypeBase->getEndLoc(), genericParamBuf);
}
}
}

std::pair<Type, ContextualTypePurpose>
FailureDiagnosis::validateContextualType(Type contextualType,
ContextualTypePurpose CTP) {
Expand Down Expand Up @@ -7483,19 +7364,6 @@ bool FailureDiagnosis::diagnoseAmbiguousGenericParameters() {
void FailureDiagnosis::
diagnoseAmbiguousGenericParameter(GenericTypeParamType *paramTy,
Expr *anchor) {
auto &tc = CS.getTypeChecker();

// The generic parameter may come from the explicit type in a cast expression.
if (auto *ECE = dyn_cast_or_null<ExplicitCastExpr>(anchor)) {
tc.diagnose(ECE->getLoc(), diag::unbound_generic_parameter_cast,
paramTy, ECE->getCastTypeLoc().getType())
.highlight(ECE->getCastTypeLoc().getSourceRange());

// Emit a note specifying where this came from, if we can find it.
noteGenericParameterSource(ECE->getCastTypeLoc(), paramTy, CS);
return;
}

// A very common cause of this diagnostic is a situation where a closure expr
// has no inferred type, due to being a multiline closure. Check to see if
// this is the case and (if so), speculatively diagnose that as the problem.
Expand All @@ -7513,58 +7381,15 @@ diagnoseAmbiguousGenericParameter(GenericTypeParamType *paramTy,

// Otherwise, emit an error message on the expr we have, and emit a note
// about where the generic parameter came from.
tc.diagnose(expr->getLoc(), diag::unbound_generic_parameter, paramTy);

// If we have an anchor, drill into it to emit a
// "note: generic parameter declared here".
if (!anchor) return;


if (auto TE = dyn_cast<TypeExpr>(anchor)) {
// Emit a note specifying where this came from, if we can find it.
noteGenericParameterSource(TE->getTypeLoc(), paramTy, CS);
if (!anchor) {
auto &tc = CS.getTypeChecker();
tc.diagnose(expr->getLoc(), diag::unbound_generic_parameter, paramTy);
return;
}

ConcreteDeclRef resolved;

// Simple case: direct reference to a declaration.
if (auto dre = dyn_cast<DeclRefExpr>(anchor))
resolved = dre->getDeclRef();

// Simple case: direct reference to a declaration.
if (auto MRE = dyn_cast<MemberRefExpr>(anchor))
resolved = MRE->getMember();

if (auto OCDRE = dyn_cast<OtherConstructorDeclRefExpr>(anchor))
resolved = OCDRE->getDeclRef();


// We couldn't resolve the locator to a declaration, so we're done.
if (!resolved)
return;

auto decl = resolved.getDecl();
if (auto FD = dyn_cast<FuncDecl>(decl)) {
auto name = FD->getFullName();
auto diagID = name.isOperator() ? diag::note_call_to_operator
: diag::note_call_to_func;
tc.diagnose(decl, diagID, name);
return;
}

// FIXME: Specialize for implicitly-generated constructors.
if (isa<ConstructorDecl>(decl)) {
tc.diagnose(decl, diag::note_call_to_initializer);
return;
}

if (auto PD = dyn_cast<ParamDecl>(decl)) {
tc.diagnose(decl, diag::note_init_parameter, PD->getName());
return;
}

// FIXME: Other decl types too.
MissingGenericArgumentsFailure failure(expr, CS, {paramTy},
CS.getConstraintLocator(anchor));
failure.diagnoseAsError();
}


Expand Down