Merge pull request #79371 from cachemeifyoucan/eng/PR-144810862

[Caching] Fix a bug when emitting diagnostics from nested macros

Author: cachemeifyoucan

lib/Frontend/CachedDiagnostics.cpp

@@ -348,7 +348,7 @@ unsigned DiagnosticSerializer::getFileIDFromBufferID(SourceManager &SM,
 
   Files.emplace_back(std::move(File));
   Allocated.insert({Idx, ++CurrentFileID});
-
+  unsigned NewFileID = CurrentFileID;
 
   auto Info = SM.getGeneratedSourceInfo(Idx);
   auto convertGeneratedFileInfo =
@@ -364,7 +364,7 @@ unsigned DiagnosticSerializer::getFileIDFromBufferID(SourceManager &SM,
     GeneratedFileInfo.emplace_back(std::move(GI));
   }
 
-  return CurrentFileID;
+  return NewFileID;
 }
 
 SerializedSourceLoc

test/CAS/cached_diagnostics_macro.swift

@@ -49,12 +49,23 @@ public struct CallDeprecatedMacro: ExpressionMacro {
   }
 }
 
+public struct ToMyWarningMacro: ExpressionMacro {
+   public static func expansion(
+     of macro: some FreestandingMacroExpansionSyntax,
+     in context: some MacroExpansionContext
+   ) throws -> ExprSyntax {
+     return "#myWarning(\"\")"
+  }
+}
+
 //--- main.swift
 @freestanding(expression) macro myWarning(_ message: String) = #externalMacro(module: "MacroDefinition", type: "CallDeprecatedMacro")
+@freestanding(expression) macro toMyWarning(_ message: String) = #externalMacro(module: "MacroDefinition", type: "ToMyWarningMacro")
 
 @available(*, deprecated)
 func testDeprecated() {}
 
 func testDiscardableStringify(x: Int) {
+  #toMyWarning("this is a warning")
   #myWarning("this is a warning")
 }