[NFC] Avoid violating same-filename rule in tests

…and modify resolveFileIDConflicts() to diagnose any such violations instead of asserting.

Swift does not allow any two files in the same module to have the same filename, even if they are in different directories. However, this is enforced in the driver, so tests that invoke the frontend directly can violate it. Turns out that a couple of those snuck into the test suite at various points.

This commit updates those tests. It also causes the frontend to diagnose the duplicate filename error just as the driver would have, which should help us understand what happened more easily if this crops up again in the future.

NFC, since invoking the frontend directly is unsupported.

Author: beccadax

include/swift/AST/DiagnosticsCommon.def

@@ -122,6 +122,14 @@ WARNING(pound_source_location_creates_pound_file_conflicts,none,
 NOTE(fixit_correct_source_location_file,none,
      "change file in '#sourceLocation' to '%0'", (StringRef))
 
+// Usually, but not always, emitted from the driver
+ERROR(error_two_files_same_name,none,
+      "filename \"%0\" used twice: '%1' and '%2'",
+      (StringRef, StringRef, StringRef))
+NOTE(note_explain_two_files_same_name,none,
+     "filenames are used to distinguish private declarations with the same "
+     "name", ())
+
 //------------------------------------------------------------------------------
 // MARK: Circular reference diagnostics
 //------------------------------------------------------------------------------

include/swift/AST/DiagnosticsDriver.def

@@ -104,13 +104,6 @@ WARNING(warn_arclite_not_found_when_link_objc_runtime,none,
         "unable to find Objective-C runtime support library 'arclite'; "
         "pass '-no-link-objc-runtime' to silence this warning", ())
 
-ERROR(error_two_files_same_name,none,
-      "filename \"%0\" used twice: '%1' and '%2'",
-      (StringRef, StringRef, StringRef))
-NOTE(note_explain_two_files_same_name,none,
-     "filenames are used to distinguish private declarations with the same "
-     "name", ())
-
 WARNING(warn_cannot_stat_input,none,
         "unable to determine when '%0' was last modified: %1",
         (StringRef, StringRef))

lib/AST/Module.cpp

@@ -2416,7 +2416,14 @@ resolveFileIDConflicts(const ModuleDecl *module, StringRef fileString,
 
     // Don't diagnose #sourceLocations that match the physical file.
     if (pathPair.second.physicalFileLoc.isValid()) {
-      assert(isWinner && "physical files should always win; duplicate name?");
+      if (!isWinner) {
+        // The driver is responsible for diagnosing this, but naughty people who
+        // have directly invoked the frontend could make it happen here instead.
+        StringRef filename = llvm::sys::path::filename(winner);
+        diags.diagnose(SourceLoc(), diag::error_two_files_same_name,
+                       filename, winner, pathPair.first());
+        diags.diagnose(SourceLoc(), diag::note_explain_two_files_same_name);
+      }
       continue;
     }
 

test/SILOptimizer/Inputs/specialize_inherited_multifile.swift renamed to test/SILOptimizer/Inputs/specialize_inherited_multifile_other.swift

@@ -1,5 +1,5 @@
 
-// RUN: %target-swift-frontend -module-name specialize_inherited_multifile -primary-file %s %S/Inputs/specialize_inherited_multifile.swift -O -emit-sil -sil-verify-all | %FileCheck %s
+// RUN: %target-swift-frontend -module-name specialize_inherited_multifile -primary-file %s %S/Inputs/specialize_inherited_multifile_other.swift -O -emit-sil -sil-verify-all | %FileCheck %s
 
 @_optimize(none) func takesBase<T : Base>(t: T) {}
 

test/SILOptimizer/specialize_inherited_multifile.swift

@@ -1,7 +1,7 @@
 // REQUIRES: asserts
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend -emit-module -module-name Multi -o %t/multi-file.swiftmodule -primary-file %s %S/Inputs/multi-file-type-eraser.swift
-// RUN: %target-swift-frontend -emit-module -module-name Multi -o %t/multi-file-2.swiftmodule %s -primary-file %S/Inputs/multi-file-type-eraser.swift
+// RUN: %target-swift-frontend -emit-module -module-name Multi -o %t/multi-file.swiftmodule -primary-file %s %S/Inputs/multi-file-type-eraser-other.swift
+// RUN: %target-swift-frontend -emit-module -module-name Multi -o %t/multi-file-2.swiftmodule %s -primary-file %S/Inputs/multi-file-type-eraser-other.swift
 
 // RUN: %target-swift-frontend -emit-module -module-name Multi %t/multi-file.swiftmodule %t/multi-file-2.swiftmodule -o %t -print-stats 2>&1 | %FileCheck %s
 // RUN: %target-swift-frontend -emit-module -module-name Multi %t/multi-file-2.swiftmodule %t/multi-file.swiftmodule -o %t -print-stats 2>&1 | %FileCheck %s