[Dependency Scanning] Discard and diagnose discovered binary modules built for an incompatible target

include/swift/AST/DiagnosticsSema.def

@@ -1290,15 +1290,6 @@ REMARK(module_api_import_aliases,none,
        "%select{, which reexports definition from %2|}3",
        (const Decl *, ModuleDecl *, ModuleDecl *, bool))
 
-REMARK(dependency_scan_skip_module_invalid,none,
-       "module file '%0' skipped by the dependency scan because it is "
-       "incompatible with this Swift compiler: %1", (StringRef, StringRef))
-WARNING(skip_module_not_testable,none,
-        "ignore swiftmodule built without '-enable-testing': %0", (StringRef))
-WARNING(dependency_scan_module_incompatible, none,
-        "module file '%0' is incompatible with this Swift compiler: %1",
-        (StringRef, StringRef))
-
 REMARK(macro_loaded,none,
        "loaded macro implementation module %0 from "
        "%select{shared library '%2'|executable '%2'|"
@@ -2377,9 +2368,11 @@ ERROR(alignment_not_power_of_two,none,
       "alignment value must be a power of two", ())
 
 // Dependency Scanning
-ERROR(dependency_scan_module_not_found, none, "Unable to find module dependency: '%0'", (StringRef))
+ERROR(dependency_scan_module_not_found, none, "unable to resolve module dependency: '%0'", (StringRef))
+
 GROUPED_ERROR(dependency_scan_module_not_found_on_specified_search_paths, MissingModuleOnKnownPaths, none,
-              "Compilation search paths unable to resolve module dependency: '%0'", (StringRef))
+              "compilation search paths unable to resolve module dependency: '%0'", (StringRef))
+
 NOTE(unresolved_import_location,none,
      "also imported here", ())
 NOTE(dependency_as_imported_by_main_module,none,
@@ -2388,10 +2381,21 @@ NOTE(dependency_as_imported_by, none,
      "a dependency of %select{Swift|Clang}2 module '%0': '%1'", (StringRef, StringRef, bool))
 NOTE(inherited_search_path_resolves_module,none,
      "'%0' can be found using a search path that was specified when building module '%1' ('%2'). "
-     "This search path was not explicitly specified on the current compilation.", (StringRef, StringRef, StringRef))
+     "This search path was not explicitly specified on the current compilation", (StringRef, StringRef, StringRef))
+
+ERROR(dependency_scan_compatible_swift_module_not_found, none,
+      "unable to resolve Swift module dependency to a compatible module: '%0'",
+      (StringRef))
+NOTE(dependency_scan_incompatible_module_found,none,
+     "found incompatible module '%0': %1", (StringRef, StringRef))
+
+WARNING(dependency_scan_module_incompatible, none,
+        "module file '%0' is incompatible with this Swift compiler: %1",
+        (StringRef, StringRef))
+
+ERROR(clang_dependency_scan_error, none, "clang dependency scanning failure: %0", (StringRef))
 
-ERROR(clang_dependency_scan_error, none, "Clang dependency scanner failure: %0", (StringRef))
-ERROR(clang_header_dependency_scan_error, none, "Bridging header dependency scan failure: %0", (StringRef))
+ERROR(clang_header_dependency_scan_error, none, "bridging header dependency scanning failure: %0", (StringRef))
 
 // Enum annotations
 ERROR(indirect_case_without_payload,none,

include/swift/AST/ModuleDependencies.h

@@ -133,6 +133,10 @@ struct ScannerImportStatementInfo {
     uint32_t columnNumber;
   };
 
+  ScannerImportStatementInfo(std::string importIdentifier)
+      : importIdentifier(importIdentifier), importLocations(),
+        isExported(false), accessLevel(AccessLevel::Public) {}
+
   ScannerImportStatementInfo(std::string importIdentifier, bool isExported,
                              AccessLevel accessLevel)
       : importIdentifier(importIdentifier), importLocations(),

include/swift/DependencyScan/ModuleDependencyScanner.h

@@ -43,7 +43,7 @@ class ModuleDependencyScanningWorker {
           &alreadySeenModules);
 
   /// Retrieve the module dependencies for the Swift module with the given name.
-  ModuleDependencyVector scanFilesystemForSwiftModuleDependency(
+  SwiftModuleScannerQueryResult scanFilesystemForSwiftModuleDependency(
       Identifier moduleName, bool isTestableImport = false);
 
   /// Query dependency information for header dependencies
@@ -112,6 +112,46 @@ class ModuleDependencyScanningWorker {
   friend class ModuleDependencyScanner;
 };
 
+class ModuleDependencyIssueReporter {
+private:
+  ModuleDependencyIssueReporter(DiagnosticEngine &Diagnostics)
+      : Diagnostics(Diagnostics) {}
+
+  /// Diagnose scanner failure and attempt to reconstruct the dependency
+  /// path from the main module to the missing dependency
+  void diagnoseModuleNotFoundFailure(
+      const ScannerImportStatementInfo &moduleImport,
+      const ModuleDependenciesCache &cache,
+      std::optional<ModuleDependencyID> dependencyOf,
+      std::optional<std::pair<ModuleDependencyID, std::string>>
+          resolvingSerializedSearchPath,
+      std::optional<
+          std::vector<SwiftModuleScannerQueryResult::IncompatibleCandidate>>
+          foundIncompatibleCandidates = std::nullopt);
+
+  /// Upon query failure, if incompatible binary module
+  /// candidates were found, emit a failure diagnostic
+  void diagnoseFailureOnOnlyIncompatibleCandidates(
+      const ScannerImportStatementInfo &moduleImport,
+      const std::vector<SwiftModuleScannerQueryResult::IncompatibleCandidate>
+          &candidates,
+      const ModuleDependenciesCache &cache,
+      std::optional<ModuleDependencyID> dependencyOf);
+
+  /// Emit warnings for each discovered binary Swift module
+  /// which was incompatible with the current compilation
+  /// when querying \c moduleName
+  void warnOnIncompatibleCandidates(
+      StringRef moduleName,
+      const std::vector<SwiftModuleScannerQueryResult::IncompatibleCandidate>
+          &candidates);
+
+  DiagnosticEngine &Diagnostics;
+  std::unordered_set<std::string> ReportedMissing;
+  // Restrict access to the parent scanner class.
+  friend class ModuleDependencyScanner;
+};
+
 class ModuleDependencyScanner {
 public:
   ModuleDependencyScanner(SwiftDependencyScanningService &ScanningService,
@@ -182,7 +222,7 @@ class ModuleDependencyScanner {
       StringRef mainModuleName, ModuleDependenciesCache &cache,
       llvm::function_ref<void(ModuleDependencyID)> action);
 
-  /// Performance BridgingHeader Chaining.
+  /// Perform Bridging Header Chaining.
   llvm::Error
   performBridgingHeaderChaining(const ModuleDependencyID &rootModuleID,
                                 ModuleDependenciesCache &cache,
@@ -197,12 +237,6 @@ class ModuleDependencyScanner {
   /// for a given module name.
   Identifier getModuleImportIdentifier(StringRef moduleName);
 
-  /// Diagnose scanner failure and attempt to reconstruct the dependency
-  /// path from the main module to the missing dependency.
-  void diagnoseScannerFailure(const ScannerImportStatementInfo &moduleImport,
-                              const ModuleDependenciesCache &cache,
-                              std::optional<ModuleDependencyID> dependencyOf);
-
   /// Assuming the \c `moduleImport` failed to resolve,
   /// iterate over all binary Swift module dependencies with serialized
   /// search paths and attempt to diagnose if the failed-to-resolve module
@@ -211,12 +245,12 @@ class ModuleDependencyScanner {
   std::optional<std::pair<ModuleDependencyID, std::string>>
   attemptToFindResolvingSerializedSearchPath(
       const ScannerImportStatementInfo &moduleImport,
-      const ModuleDependenciesCache &cache, const SourceLoc &importLoc);
+      const ModuleDependenciesCache &cache);
 
 private:
   const CompilerInvocation &ScanCompilerInvocation;
   ASTContext &ScanASTContext;
-  DiagnosticEngine &Diagnostics;
+  ModuleDependencyIssueReporter IssueReporter;
 
   /// The available pool of workers for filesystem module search
   unsigned NumThreads;

include/swift/Serialization/ScanningLoaders.h

@@ -18,6 +18,19 @@
 #include "swift/Serialization/SerializedModuleLoader.h"
 
 namespace swift {
+
+/// Result of looking up a Swift module on the current filesystem
+/// search paths.
+struct SwiftModuleScannerQueryResult {
+  struct IncompatibleCandidate {
+    std::string path;
+    std::string incompatibilityReason;
+  };
+
+  std::vector<IncompatibleCandidate> incompatibleCandidates;
+  std::optional<ModuleDependencyInfo> foundDependencyInfo;
+};
+
 /// A module "loader" that looks for .swiftinterface and .swiftmodule files
 /// for the purpose of determining dependencies, but does not attempt to
 /// load the module files.
@@ -60,7 +73,8 @@ class SwiftModuleScanner : public SerializedModuleLoaderBase {
   std::vector<std::string> swiftModuleClangCC1CommandLineArgs;
 
 public:
-  std::optional<ModuleDependencyInfo> dependencies;
+  std::vector<SwiftModuleScannerQueryResult::IncompatibleCandidate> incompatibleCandidates;
+  std::optional<ModuleDependencyInfo> foundDependencyInfo;
 
   SwiftModuleScanner(ASTContext &ctx, ModuleLoadingMode LoadMode,
                      InterfaceSubContextDelegate &astDelegate,
@@ -74,7 +88,7 @@ class SwiftModuleScanner : public SerializedModuleLoaderBase {
         swiftModuleClangCC1CommandLineArgs(swiftModuleClangCC1CommandLineArgs)  {}
 
   /// Perform a filesystem search for a Swift module with a given name
-  llvm::SmallVector<std::pair<ModuleDependencyID, ModuleDependencyInfo>, 1>
+  SwiftModuleScannerQueryResult
   lookupSwiftModule(Identifier moduleName, bool isTestableImport);
 };
 } // namespace swift

include/swift/Serialization/SerializedModuleLoader.h

@@ -185,6 +185,7 @@ class SerializedModuleLoaderBase : public ModuleLoader {
                                         bool isFramework,
                                         bool isRequiredOSSAModules,
                                         StringRef SDKName,
+                                        const llvm::Triple &target,
                                         StringRef packageName,
                                         llvm::vfs::FileSystem *fileSystem,
                                         PathObfuscator &recoverer);

include/swift/Serialization/Validation.h

@@ -23,10 +23,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
-
-namespace llvm {
-class Triple;
-}
+#include "llvm/TargetParser/Triple.h"
 
 namespace swift {
 
@@ -296,6 +293,8 @@ struct SearchPath {
 /// compiled with -enable-ossa-modules.
 /// \param requiredSDK If not empty, only accept modules built with
 /// a compatible SDK. The StringRef represents the canonical SDK name.
+/// \param target The target triple of the current compilation for
+/// validating that the module we are attempting to load is compatible.
 /// \param[out] extendedInfo If present, will be populated with additional
 /// compilation options serialized into the AST at build time that may be
 /// necessary to load it properly.
@@ -307,7 +306,8 @@ ValidationInfo validateSerializedAST(
     ExtendedValidationInfo *extendedInfo = nullptr,
     SmallVectorImpl<SerializationOptions::FileDependency> *dependencies =
         nullptr,
-    SmallVectorImpl<SearchPath> *searchPaths = nullptr);
+    SmallVectorImpl<SearchPath> *searchPaths = nullptr,
+    std::optional<llvm::Triple> target = std::nullopt);
 
 /// Emit diagnostics explaining a failure to load a serialized AST.
 ///