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☣️[Sema] Transform initializers into coercions for conforming numeric literals #15311

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☣️[Sema] Transform initializers into coercions for conforming numeric literals #15311

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54 changes: 54 additions & 0 deletions lib/Sema/TypeCheckConstraints.cpp
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Expand Up @@ -787,6 +787,10 @@ namespace {
/// Simplify a key path expression into a canonical form.
void resolveKeyPathExpr(KeyPathExpr *KPE);

/// Simplify constructs like `UInt32(1)` into `1 as UInt32` if
/// the type conforms to the expected literal protocol.
Expr *simplifyInitWithLiteral(Expr *E);

public:
PreCheckExpression(TypeChecker &tc, DeclContext *dc) : TC(tc), DC(dc) { }

Expand Down Expand Up @@ -989,6 +993,9 @@ namespace {
return KPE;
}

if (auto *simplified = simplifyInitWithLiteral(expr))
return simplified;

return expr;
}

Expand Down Expand Up @@ -1547,6 +1554,53 @@ void PreCheckExpression::resolveKeyPathExpr(KeyPathExpr *KPE) {
KPE->resolveComponents(TC.Context, components);
}

Expr *PreCheckExpression::simplifyInitWithLiteral(Expr *E) {
auto *call = dyn_cast<CallExpr>(E);
if (!call || call->getNumArguments() != 1)
return nullptr;

auto *typeExpr = dyn_cast<TypeExpr>(call->getFn());
if (!typeExpr)
return nullptr;

auto *argExpr = call->getArg()->getSemanticsProvidingExpr();
auto *number = dyn_cast<NumberLiteralExpr>(argExpr);
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Shouldn't this apply to all literal kinds? For example, Set([1, 2, 3])?

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Yes, I just tried with NumberLiteralExpr because I ran into problem with failable initializer in swiftpm clashing with ExpressibleByStringLiteral but still wanted to get some performance numbers, and NumberLiteralExpr since to be the biggest pain point for stdlib folks anyway.

if (!number)
return nullptr;

auto *protocol = TC.getLiteralProtocol(number);
if (!protocol)
return nullptr;

Type type;
if (auto *rep = typeExpr->getTypeRepr()) {
TypeResolutionOptions options;
options |= TypeResolutionFlags::AllowUnboundGenerics;
options |= TypeResolutionFlags::InExpression;
type = TC.resolveType(rep, DC, options);
} else {
type = typeExpr->getTypeLoc().getType();
}

if (!type)
return nullptr;

ConformanceCheckOptions options;
options |= ConformanceCheckFlags::InExpression;
options |= ConformanceCheckFlags::SuppressDependencyTracking;
options |= ConformanceCheckFlags::SkipConditionalRequirements;

auto result = TC.conformsToProtocol(type, protocol, DC, options);
if (result) {
auto *expr =
new (TC.Context) CoerceExpr(argExpr, {}, typeExpr->getTypeRepr());
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We're losing a bunch of the source information in doing this. Should we try to make this a constraint-system change and have CSApply fix up the result, rather than turning it into a CoerceExpr?

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Yes, that's on my agenda to do next.

expr->setImplicit();
return expr;
}

return nullptr;
}

/// \brief Clean up the given ill-formed expression, removing any references
/// to type variables and setting error types on erroneous expression nodes.
void CleanupIllFormedExpressionRAII::doIt(Expr *expr, ASTContext &Context) {
Expand Down