[CodeCompletion] Do our best to set NotRecommended on other-module results

These results are cached, so we can't use the type-relation.  Instead we
use a small hack of checking the textual return type for "Void".  This
is obviously not ideal, but it lets us detect the most important cases.

rdar://problem/22810741

Author: benlangmuir

test/SourceKit/CodeComplete/complete_cache.swift

@@ -13,3 +13,36 @@ import Foo
 // RUN: FileCheck %s < %t.completions1
 // RUN: FileCheck %s < %t.completions2
 // CHECK: key.name: "FooStruct
+
+// RUN: %complete-test -raw -tok=VOID_1 %s -- -F %S/../Inputs/libIDE-mock-sdk | FileCheck %s -check-prefix=VOID_1
+// RUN: %complete-test -raw -tok=VOID_2 %s -- -F %S/../Inputs/libIDE-mock-sdk | FileCheck %s -check-prefix=VOID_1
+// RUN: %complete-test -raw -tok=VOID_3 %s -- -F %S/../Inputs/libIDE-mock-sdk | FileCheck %s -check-prefix=VOID_3
+func test1() {
+  _ = #^VOID_1,fooFunc^#
+}
+func test2() {
+  for i in 1...#^VOID_2,fooFunc^# {}
+}
+// VOID_1: key.name: "fooHelperSubFunc1(:)",
+// VOID_1-NEXT: key.sourcetext:
+// VOID_1-NEXT: key.description:
+// VOID_1-NEXT: key.typename: "Int32",
+// VOID_1-NEXT: key.context: source.codecompletion.context.othermodule,
+// VOID_1-NEXT: key.moduleimportdepth: 2,
+// VOID_1-NEXT: key.num_bytes_to_erase: 0,
+// VOID_1-NEXT: key.substructure:
+
+// VOID_1: key.name: "fooFuncNoreturn1()",
+// VOID_1-NEXT: key.sourcetext:
+// VOID_1-NEXT: key.description:
+// VOID_1-NEXT: key.typename: "Void",
+// VOID_1-NEXT: key.context: source.codecompletion.context.othermodule,
+// VOID_1-NEXT: key.moduleimportdepth: 1,
+// VOID_1-NEXT: key.num_bytes_to_erase: 0,
+// VOID_1-NEXT: key.not_recommended: 1,
+// VOID_1-NEXT: key.substructure:
+
+func test3() {
+  #^VOID_3,fooFunc^# {}
+}
+// VOID_3-NOT: key.not_recommended

tools/SourceKit/lib/SwiftLang/CodeCompletion.h

@@ -123,6 +123,8 @@ class CompletionBuilder {
   CompletionSink &sink;
   SwiftResult &current;
   bool modified = false;
+  bool isNotRecommended;
+  Completion::NotRecommendedReason notRecommendedReason;
   SemanticContextKind semanticContext;
   CodeCompletionString *completionString;
   llvm::SmallVector<char, 64> originalName;
@@ -145,6 +147,13 @@ class CompletionBuilder {
     moduleImportDepth = value;
   }
 
+  void setNotRecommended(Completion::NotRecommendedReason Reason) {
+    modified = true;
+    notRecommendedReason = Reason;
+    if (Reason != Completion::NoReason)
+      isNotRecommended = true;
+  }
+
   void setSemanticContext(SemanticContextKind kind) {
     modified = true;
     semanticContext = kind;

tools/SourceKit/lib/SwiftLang/CodeCompletionOrganizer.cpp

@@ -100,9 +100,24 @@ std::vector<Completion *> SourceKit::CodeCompletion::extendCompletions(
   std::vector<Completion *> results;
   for (auto *result : swiftResults) {
     CompletionBuilder builder(sink, *result);
-    if (result->getSemanticContext() == SemanticContextKind::OtherModule)
+    if (result->getSemanticContext() == SemanticContextKind::OtherModule) {
       builder.setModuleImportDepth(depth.lookup(result->getModuleName()));
 
+      if (info.completionContext->HasExpectedTypeRelation &&
+          result->getKind() == Completion::Declaration) {
+        // FIXME: because other-module results are cached, they will not be
+        // given a type-relation of invalid.  As a hack, we look at the text of
+        // the result type and look for 'Void'.
+        for (auto &chunk : result->getCompletionString()->getChunks()) {
+          using ChunkKind = ide::CodeCompletionString::Chunk::ChunkKind;
+          if (chunk.is(ChunkKind::TypeAnnotation) && chunk.hasText() &&
+              chunk.getText() == "Void") {
+            builder.setNotRecommended(Completion::TypeMismatch);
+          }
+        }
+      }
+    }
+
     if (prefix) {
       builder.setPrefix(prefix->getCompletionString());
       builder.setSemanticContext(prefix->getSemanticContext());
@@ -1116,6 +1131,8 @@ void CompletionBuilder::getDescription(SwiftResult *result, raw_ostream &OS,
 
 CompletionBuilder::CompletionBuilder(CompletionSink &sink, SwiftResult &base)
     : sink(sink), current(base) {
+  isNotRecommended = current.isNotRecommended();
+  notRecommendedReason = current.getNotRecommendedReason();
   semanticContext = current.getSemanticContext();
   completionString =
       const_cast<CodeCompletionString *>(current.getCompletionString());
@@ -1158,8 +1175,8 @@ Completion *CompletionBuilder::finish() {
     if (current.getKind() == SwiftResult::Declaration) {
       base = SwiftResult(semanticContext, current.getNumBytesToErase(),
                          completionString, current.getAssociatedDeclKind(),
-                         current.getModuleName(), current.isNotRecommended(),
-                         current.getNotRecommendedReason(),
+                         current.getModuleName(), isNotRecommended,
+                         notRecommendedReason,
                          current.getBriefDocComment(),
                          current.getAssociatedUSRs(),
                          current.getDeclKeywords());