[ModuleInterface] Support missing imports with the AliasModuleNames workaround

If there's a reference in API to a module that's not imported, the
import is inserted automatically in the swiftinterface. This ensures the
inserted import is correctly aliased in AliasModuleNames mode.

Author: xymus

lib/Frontend/ModuleInterfaceSupport.cpp

@@ -74,6 +74,7 @@ static void printToolVersionAndFlagsComment(raw_ostream &out,
                            ModuleDecl::ImportFilterKind::Exported,
                            ModuleDecl::ImportFilterKind::SPIOnly,
                            ModuleDecl::ImportFilterKind::SPIAccessControl});
+    M->getMissingImportedModules(imports);
     for (ImportedModule import: imports) {
       StringRef importedName = import.importedModule->getNameStr();
       if (aliasTargets.insert(importedName).second) {

test/Sema/missing-import-inlinable-code.swift

@@ -24,6 +24,12 @@
 // RUN: %target-swift-emit-module-interface(%t/ClientFixed.swiftinterface)  %t/clientFileA-Swift5.swift %t/clientFileB.swift -I %t
 // RUN: %target-swift-typecheck-module-from-interface(%t/ClientFixed.swiftinterface) -I %t
 
+/// The inserted missing imports should be aliased.
+// RUN: %target-swift-emit-module-interface(%t/ClientFixed.swiftinterface) %t/clientFileA-Swift5.swift %t/clientFileB.swift -I %t -alias-module-names-in-module-interface
+// RUN: %target-swift-typecheck-module-from-interface(%t/ClientFixed.swiftinterface) -I %t
+// RUN: cat %t/ClientFixed.swiftinterface | %FileCheck -check-prefix ALIASED %s
+// ALIASED: import Module___libB
+
 // REQUIRES: asserts
 
 // BEGIN empty.swift