Fix keypath-as-function crasher

The autoclosures generated for the keypath-as-function feature were not added to the list of closures that needed captures computed. In top-level code, this caused a crash. Fixes rdar://problem/56055600.

Author: beccadax

lib/AST/CaptureInfo.cpp

@@ -78,7 +78,7 @@ getLocalCaptures(SmallVectorImpl<CapturedValue> &Result) const {
   }
 }
 
-void CaptureInfo::dump() const {
+LLVM_ATTRIBUTE_USED void CaptureInfo::dump() const {
   print(llvm::errs());
   llvm::errs() << '\n';
 }

lib/Sema/CSApply.cpp

@@ -4500,6 +4500,10 @@ namespace {
       outerClosure->setType(outerClosureTy);
       cs.cacheType(outerClosure);
 
+      // The inner closure at least will definitely have a capture.
+      cs.TC.ClosuresWithUncomputedCaptures.push_back(outerClosure);
+      cs.TC.ClosuresWithUncomputedCaptures.push_back(closure);
+
       // let outerApply = "\( outerClosure )( \(E) )"
       auto outerApply = CallExpr::createImplicit(ctx, outerClosure, {E}, {});
       outerApply->setType(closureTy);

validation-test/compiler_crashers_2_fixed/0209-rdar56055600.swift

@@ -0,0 +1,2 @@
+// RUN: %target-swift-frontend %s -emit-silgen -o /dev/null
+let _: ([Int]) -> Int = \[Int].count