[Macros] Pass the attached macro mangling to ASTGen to use as the discriminator

when creating the macro expansion context.

Author: hborla

lib/ASTGen/Sources/ASTGen/Macros.swift

@@ -293,6 +293,8 @@ private func findSyntaxNodeInSourceFile<Node: SyntaxProtocol>(
 func expandAttachedMacro(
   diagEnginePtr: UnsafeMutablePointer<UInt8>,
   macroPtr: UnsafeRawPointer,
+  discriminatorText: UnsafePointer<UInt8>,
+  discriminatorTextLength: Int,
   rawMacroRole: UInt8,
   customAttrSourceFilePtr: UnsafeRawPointer,
   customAttrSourceLocPointer: UnsafePointer<UInt8>?,
@@ -344,7 +346,13 @@ func expandAttachedMacro(
   sourceManager.insert(declarationSourceFilePtr)
 
   // Create an expansion context
-  let context = sourceManager.createMacroExpansionContext()
+  let discriminatorBuffer = UnsafeBufferPointer(
+    start: discriminatorText, count: discriminatorTextLength
+  )
+  let discriminator = String(decoding: discriminatorBuffer, as: UTF8.self)
+  let context = sourceManager.createMacroExpansionContext(
+    discriminator: discriminator
+  )
 
   let macroName = customAttrNode.attributeName.description
   var evaluatedSyntaxStr: String

lib/Sema/TypeCheckMacros.cpp

@@ -58,6 +58,8 @@ extern "C" ptrdiff_t swift_ASTGen_expandFreestandingMacro(
 
 extern "C" ptrdiff_t swift_ASTGen_expandAttachedMacro(
     void *diagEngine, void *macro,
+    const char *discriminator,
+    ptrdiff_t discriminatorLength,
     uint32_t rawMacroRole,
     void *customAttrSourceFile,
     const void *customAttrSourceLocation,
@@ -867,6 +869,7 @@ evaluateAttachedMacro(MacroDecl *macro, Decl *attachedTo, CustomAttr *attr,
   // Evaluate the macro.
   NullTerminatedStringRef evaluatedSource;
 
+  std::string discriminator;
   auto macroDef = macro->getDefinition();
   switch (macroDef.kind) {
   case MacroDefinition::Kind::Undefined:
@@ -932,11 +935,18 @@ evaluateAttachedMacro(MacroDecl *macro, Decl *attachedTo, CustomAttr *attr,
     if (auto var = dyn_cast<VarDecl>(attachedTo))
       searchDecl = var->getParentPatternBinding();
 
+    {
+      Mangle::ASTMangler mangler;
+      discriminator =
+        mangler.mangleAttachedMacroExpansion(attachedTo, attr, role);
+    }
+
     const char *evaluatedSourceAddress;
     ptrdiff_t evaluatedSourceLength;
     swift_ASTGen_expandAttachedMacro(
         &ctx.Diags,
         externalDef.opaqueHandle,
+        discriminator.data(), discriminator.size(),
         static_cast<uint32_t>(role),
         astGenAttrSourceFile, attr->AtLoc.getOpaquePointerValue(),
         astGenDeclSourceFile, searchDecl->getStartLoc().getOpaquePointerValue(),
@@ -955,14 +965,7 @@ evaluateAttachedMacro(MacroDecl *macro, Decl *attachedTo, CustomAttr *attr,
   }
 
   // Figure out a reasonable name for the macro expansion buffer.
-  std::string discriminator;
-  std::string bufferName;
-  {
-    Mangle::ASTMangler mangler;
-    discriminator =
-      mangler.mangleAttachedMacroExpansion(attachedTo, attr, role);
-    bufferName = adjustMacroExpansionBufferName(discriminator);
-  }
+  std::string bufferName = adjustMacroExpansionBufferName(discriminator);
 
   // Dump macro expansions to standard output, if requested.
   if (ctx.LangOpts.DumpMacroExpansions) {

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -780,8 +780,7 @@ public struct WrapInType: PeerMacro {
       funcDecl
       .with(
         \.identifier,
-         // FIXME: 'createUniqueName' starts with an int
-         "method_\(context.createUniqueName(funcDecl.identifier.text))"
+         "\(context.createUniqueName(funcDecl.identifier.text))"
       )
       .with(
         \.signature,
@@ -800,10 +799,9 @@ public struct WrapInType: PeerMacro {
       )
       .with(\.attributes, newAttributeList)
 
-    // FIXME: 'createUniqueName' starts with an int
     let structType: DeclSyntax =
       """
-      struct Wrapper_\(context.createUniqueName(funcDecl.identifier.text)) {
+      struct \(context.createUniqueName(funcDecl.identifier.text)) {
         \(method)
       }
       """

test/Macros/macro_expand_peers.swift

@@ -34,8 +34,8 @@ func global(a: Int, b: String) {
 }
 
 // CHECK-DUMP: @__swiftmacro_18macro_expand_peers6global1a1bySi_SStF10wrapInTypefMp_.swift
-// CHECK-DUMP: struct Wrapper_6globalfMu0_ {
-// CHECK-DUMP:   func method_6globalfMu_(a: Int, b: String)  {
+// CHECK-DUMP: struct $s18macro_expand_peers6global1a1bySi_SStF10wrapInTypefMp_6globalfMu0_ {
+// CHECK-DUMP:   func $s18macro_expand_peers6global1a1bySi_SStF10wrapInTypefMp_6globalfMu_(a: Int, b: String)  {
 // CHECK-DUMP:     global(a: a, b: b)
 // CHECK-DUMP:   }
 // CHECK-DUMP: }