Tweak redecl checking’s handling of generated code

Macro expansions are now treated like a part of the source file they belong to, for purposes of the “second declaration is the one that’s diagnosed” rule. This helps stabilize a behavior that was easy to perturb.

Author: beccadax

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -618,15 +618,15 @@ static void checkGenericParams(GenericContext *ownerCtx) {
 /// Returns \c true if \p current and \p other are in the same source file
 /// \em and \c current appears before \p other in that file.
 static bool isBeforeInSameFile(Decl *current, Decl *other) {
-  if (current->getDeclContext()->getParentSourceFile() !=
-                  other->getDeclContext()->getParentSourceFile())
+  if (current->getDeclContext()->getOutermostParentSourceFile() !=
+                  other->getDeclContext()->getOutermostParentSourceFile())
     return false;
 
-  if (!current->getLoc().isValid())
+  if (current->getLoc().isInvalid() || other->getLoc().isInvalid())
     return false;
 
   return current->getASTContext().SourceMgr
-                        .isBeforeInBuffer(current->getLoc(), other->getLoc());
+                        .isBefore(current->getLoc(), other->getLoc());
 }
 
 template <typename T>

test/Macros/macro_expand.swift

@@ -135,6 +135,23 @@ class HasStoredPropertyClassInvalid {
   // CHECK-DIAGS: @__swiftmacro_9MacroUser0023macro_expandswift_elFCffMX[[@LINE-2]]_2_33_{{.*}}AddStoredPropertyfMf_.swift:1:22: error: covariant 'Self' type cannot be referenced from a stored property initializer
 }
 
+// Redeclaration checking should behave as though expansions are part of the
+// source file.
+struct RedeclChecking {
+  #varValue
+
+  // expected-error@+1 {{invalid redeclaration of 'value'}}
+  var value: Int { 0 }
+}
+
+// CHECK-DIAGS: macro_expand.swift:[[@LINE-3]]:7: error: invalid redeclaration of 'value'
+// CHECK-DIAGS: @__swiftmacro_9MacroUser0023macro_expandswift_elFCffMX[[@LINE-8]]_2_33_4361AD9339943F52AE6186DD51E04E91Ll8varValuefMf_.swift:1:5: note: 'value' previously declared here
+// CHECK-DIAGS: CONTENTS OF FILE @__swiftmacro_9MacroUser0023macro_expandswift_elFCffMX[[@LINE-9]]_2_33_4361AD9339943F52AE6186DD51E04E91Ll8varValuefMf_.swift:
+// CHECK-DIAGS: var value: Int {
+// CHECK-DIAGS:     1
+// CHECK-DIAGS: }
+// CHECK-DIAGS: END CONTENTS OF FILE
+
 @attached(body)
 public macro ThrowCancellation() = #externalMacro(module: "MacroDefinition", type: "ThrowCancellationMacro")