@dynamicCallable
struct A {
  init(_ x: Int = 0) {}
  func dynamicallyCall(withArguments args: [Int]) {}
}

A()()

/tmp/init.swift:7:1: error: type of expression is ambiguous without more context
A()()
^~~
Assertion failed: (hasType(E) && "Expected type to have been set!"), function getType, file /Users/harlan/Swift/swift/lib/Sema/ConstraintSystem.h, line 1683.
Stack dump:
0.  Program arguments: /Users/harlan/Swift/build/Ninja-ReleaseAssert/swift-macosx-x86_64/bin/swift -frontend -emit-sil -primary-file /tmp/init.swift -target x86_64-apple-darwin18.2.0 -enable-objc-interop -color-diagnostics -module-name init -o - 
1.  While type-checking statement at [/tmp/init.swift:7:1 - line:7:5] RangeText="A()("
2.  While type-checking expression at [/tmp/init.swift:7:1 - line:7:5] RangeText="A()("
0  swift                    0x00000001043dd425 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1  swift                    0x00000001043dc408 llvm::sys::RunSignalHandlers() + 248
2  swift                    0x00000001043dda32 SignalHandler(int) + 258
3  libsystem_platform.dylib 0x00007fff681c7b3d _sigtramp + 29
4  swift                    0x00000001056d8be5 cmark_strbuf__initbuf + 133936
5  libsystem_c.dylib        0x00007fff680851c9 abort + 127
6  libsystem_c.dylib        0x00007fff6804d868 basename_r + 0
7  swift                    0x000000010154af94 swift::constraints::ConstraintSystem::getType(swift::Expr const*) const + 356
8  swift                    0x0000000101423937 (anonymous namespace)::ExprWalker::walkToExprPost(swift::Expr*) + 55
9  swift                    0x0000000101850a16 swift::Expr::walk(swift::ASTWalker&) + 118
10 swift                    0x000000010141b3ae swift::constraints::ConstraintSystem::applySolution(swift::constraints::Solution&, swift::Expr*, swift::Type, bool, bool) + 510
11 swift                    0x000000010154abb0 swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem*) + 1136
12 swift                    0x00000001015dee08 swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 600
13 swift                    0x00000001015ddfc8 bool (anonymous namespace)::StmtChecker::typeCheckStmt<swift::BraceStmt>(swift::BraceStmt*&) + 136
14 swift                    0x00000001015de0de swift::TypeChecker::typeCheckTopLevelCodeDecl(swift::TopLevelCodeDecl*) + 174
15 swift                    0x00000001015feb8e swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int, unsigned int, unsigned int, unsigned int) + 846
16 swift                    0x0000000100dc8c3c swift::CompilerInstance::parseAndTypeCheckMainFileUpTo(swift::SourceFile::ASTStage_t, swift::PersistentParserState&, swift::DelayedParsingCallbacks*, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>) + 492
17 swift                    0x0000000100dc75c3 swift::CompilerInstance::parseAndCheckTypesUpTo(swift::CompilerInstance::ImplicitImports const&, swift::SourceFile::ASTStage_t) + 435
18 swift                    0x0000000100dc6c87 swift::CompilerInstance::performSemaUpTo(swift::SourceFile::ASTStage_t) + 615
19 swift                    0x000000010051fd88 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 1192
20 swift                    0x000000010051e878 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3016
21 swift                    0x00000001004d0962 main + 690
22 libdyld.dylib            0x00007fff67fdcef9 start + 1