[CodeCompletion] Protect against a couple of null Types

Fix two crashes related to unresolved-member completion where either the
EnumDecl itself is missing, or its elements have not been type-checked.
Incidentally, resolve the type of the enum elements in the case where I
have observed this happening.

rdar://problem/26860249

Author: benlangmuir

lib/IDE/CodeCompletion.cpp

@@ -2621,6 +2621,7 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
         (EED->hasAccessibility() && !EED->isAccessibleFrom(CurrDeclContext)) ||
         shouldHideDeclFromCompletionResults(EED))
       return;
+
     CommandWordsPairs Pairs;
     CodeCompletionResultBuilder Builder(
         Sink,
@@ -2633,14 +2634,18 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
     Builder.addTextChunk(EED->getName().str());
     if (EED->hasArgumentType())
       addPatternFromType(Builder, EED->getArgumentType());
-    Type EnumType = EED->getType();
 
     // Enum element is of function type such as EnumName.type -> Int ->
     // EnumName; however we should show Int -> EnumName as the type
-    if (auto FuncType = EED->getType()->getAs<AnyFunctionType>()) {
-      EnumType = FuncType->getResult();
+    Type EnumType;
+    if (EED->hasType()) {
+      EnumType = EED->getType();
+      if (auto FuncType = EnumType->getAs<AnyFunctionType>()) {
+        EnumType = FuncType->getResult();
+      }
     }
-    addTypeAnnotation(Builder, EnumType);
+    if (EnumType)
+      addTypeAnnotation(Builder, EnumType);
   }
 
   void addKeyword(StringRef Name, Type TypeAnnotation,
@@ -2936,14 +2941,19 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
     }
   }
 
-  bool handleEnumElement(Decl *D, DeclVisibilityKind Reason) {
+  bool handleEnumElement(ValueDecl *D, DeclVisibilityKind Reason) {
+    if (!D->hasType())
+      TypeResolver->resolveDeclSignature(D);
+
     if (auto *EED = dyn_cast<EnumElementDecl>(D)) {
       addEnumElementRef(EED, Reason, /*HasTypeContext=*/true);
       return true;
     } else if (auto *ED = dyn_cast<EnumDecl>(D)) {
       llvm::DenseSet<EnumElementDecl *> Elements;
       ED->getAllElements(Elements);
       for (auto *Ele : Elements) {
+        if (!Ele->hasType())
+          TypeResolver->resolveDeclSignature(Ele);
         addEnumElementRef(Ele, Reason, /*HasTypeContext=*/true);
       }
       return true;
@@ -3655,7 +3665,8 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
     LookupByName Lookup(*this, FuncNames);
     lookupVisibleDecls(Lookup, CurrDeclContext, TypeResolver.get(), true);
     if (HasReturn)
-      Lookup.unboxType(getReturnTypeFromContext(CurrDeclContext));
+      if (auto ReturnType = getReturnTypeFromContext(CurrDeclContext))
+        Lookup.unboxType(ReturnType);
   }
 
   static bool getPositionInTupleExpr(DeclContext &DC, Expr *Target,

test/IDE/Inputs/EnumFromOtherFile.swift

@@ -0,0 +1,5 @@
+enum EnumFromOtherFile {
+  case a(Int)
+  case b(String)
+  case c
+}

test/IDE/complete_unresolved_members.swift

@@ -41,6 +41,10 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=WITH_LITERAL_2 | FileCheck %s -check-prefix=WITH_LITERAL_1
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=WITH_LITERAL_3 | FileCheck %s -check-prefix=WITH_LITERAL_1
 
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=INVALID_1
+
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=OTHER_FILE_1 %S/Inputs/EnumFromOtherFile.swift | FileCheck %s -check-prefix=OTHER_FILE_1
+
 enum SomeEnum1 {
   case South
   case North
@@ -309,3 +313,18 @@ func testWithLiteral3() {
     }
   }
 }
+
+func testInvalid1() {
+  func invalid() -> NoSuchEnum {
+    return .#^INVALID_1^# // Don't crash.
+  }
+}
+
+func enumFromOtherFile() -> EnumFromOtherFile {
+  return .#^OTHER_FILE_1^# // Don't crash.
+}
+OTHER_FILE_1: Begin completions
+OTHER_FILE_1-DAG: Decl[EnumElement]/ExprSpecific:     b({#String#})[#(String) -> EnumFromOtherFile#];
+OTHER_FILE_1-DAG: Decl[EnumElement]/ExprSpecific:     a({#Int#})[#(Int) -> EnumFromOtherFile#];
+OTHER_FILE_1-DAG: Decl[EnumElement]/ExprSpecific:     c[#EnumFromOtherFile#];
+OTHER_FILE_1: End completions