[index] Remove import.sourcefile kind from indexing

We don't support importing source files in source code, and they only
showed up in the index under failure conditions.

include/swift/Index/IndexSymbol.h

@@ -26,7 +26,6 @@ enum class SymbolKind {
 
   Module,
   ClangModule, // FIXME: collapse into Module and use a separate Language field.
-  SourceFile,
 
   Enum,
   Struct,

lib/Index/Index.cpp

@@ -410,10 +410,6 @@ bool IndexSwiftASTWalker::visitImports(
     for (auto File : Mod->getFiles()) {
       switch (File->getKind()) {
       case FileUnitKind::Source:
-        assert(ImportKind == SymbolKind::Unknown &&
-               "cannot handle multi-file modules");
-        ImportKind = SymbolKind::SourceFile;
-        break;
       case FileUnitKind::Builtin:
       case FileUnitKind::Derived:
         break;

test/SourceKit/Indexing/index_bad_modulename.swift.response

@@ -7,27 +7,6 @@
       key.filepath: Swift.swiftmodule,
       key.hash: <hash>,
       key.is_system: 1
-    },
-    {
-      key.kind: source.lang.swift.import.sourcefile,
-      key.name: "ObjectiveC",
-      key.filepath: ObjectiveC.swift,
-      key.hash: <hash>,
-      key.dependencies: [
-        {
-          key.kind: source.lang.swift.import.module.swift,
-          key.name: "Swift",
-          key.filepath: Swift.swiftmodule,
-          key.hash: <hash>,
-          key.is_system: 1
-        },
-        {
-          key.kind: source.lang.swift.import.module.clang,
-          key.name: "ObjectiveC",
-          key.filepath: ObjectiveC.pcm,
-          key.is_system: 1
-        }
-      ]
     }
   ],
   key.entities: [

tools/SourceKit/lib/SwiftLang/SwiftIndexing.cpp

@@ -30,7 +30,6 @@ using namespace swift::index;
 
 static UIdent KindImportModuleClang("source.lang.swift.import.module.clang");
 static UIdent KindImportModuleSwift("source.lang.swift.import.module.swift");
-static UIdent KindImportSourceFile("source.lang.swift.import.sourcefile");
 
 static UIdent getUIDForDependencyKind(SymbolKind depKind) {
   switch (depKind) {
@@ -38,8 +37,6 @@ static UIdent getUIDForDependencyKind(SymbolKind depKind) {
     return KindImportModuleSwift;
   case SymbolKind::ClangModule:
     return KindImportModuleClang;
-  case SymbolKind::SourceFile:
-    return KindImportSourceFile;
   default:
     return UIdent();
   }