[Macros] Provide the freestanding macro role for expansion operations.

The compiler knows (from a macro declaration) what freestanding macro
role a macro implementation is expected to implement. Pass that through
to the macro expansion code itself, rather than guessing based on the
protocol conformances of the implementation type. We already use this
approach with attached macros, so this is more of the same.

Eliminates a crash and improves diagnostics when the freestanding macro
role and its implementation are out of sync, fixing rdar://110418969.

Author: DougGregor

lib/ASTGen/Sources/ASTGen/Macros.swift

@@ -67,6 +67,8 @@ extension MacroRole {
     case 0x10: self = .member
     case 0x20: self = .peer
     case 0x40: self = .conformance
+    case 0x80: self = .codeItem
+
     default: fatalError("unknown macro role")
     }
   }
@@ -414,6 +416,7 @@ func expandFreestandingMacro(
   macroKind: UInt8,
   discriminatorText: UnsafePointer<UInt8>,
   discriminatorTextLength: Int,
+  rawMacroRole: UInt8,
   sourceFilePtr: UnsafeRawPointer,
   sourceLocationPtr: UnsafePointer<UInt8>?,
   expandedSourcePointer: UnsafeMutablePointer<UnsafePointer<UInt8>?>,
@@ -446,18 +449,21 @@ func expandFreestandingMacro(
   )
   let discriminator = String(decoding: discriminatorBuffer, as: UTF8.self)
 
+  let macroRole = MacroRole(rawMacroRole: rawMacroRole)
   let expandedSource: String?
   switch MacroPluginKind(rawValue: macroKind)! {
   case .InProcess:
     expandedSource = expandFreestandingMacroInProcess(
       macroPtr: macroPtr,
+      macroRole: macroRole,
       diagEnginePtr: diagEnginePtr,
       expansionSyntax: expansion,
       sourceFilePtr: sourceFilePtr,
       discriminator: discriminator)
   case .Executable:
     expandedSource = expandFreestandingMacroIPC(
       macroPtr: macroPtr,
+      macroRole: macroRole,
       diagEnginePtr: diagEnginePtr,
       expansionSyntax: expansion,
       sourceFilePtr: sourceFilePtr,
@@ -485,6 +491,7 @@ func expandFreestandingMacro(
 
 func expandFreestandingMacroIPC(
   macroPtr: UnsafeRawPointer,
+  macroRole: MacroRole,
   diagEnginePtr: UnsafeMutablePointer<UInt8>,
   expansionSyntax: FreestandingMacroExpansionSyntax,
   sourceFilePtr: UnsafePointer<ExportedSourceFile>,
@@ -502,9 +509,21 @@ func expandFreestandingMacroIPC(
 
   let macro = macroPtr.assumingMemoryBound(to: ExportedExecutableMacro.self).pointee
 
+  // Map the macro role.
+  let pluginMacroRole: PluginMessage.MacroRole
+  switch macroRole {
+  case .accessor, .member, .memberAttribute, .peer, .conformance:
+    preconditionFailure("unhandled macro role for freestanding macro")
+
+  case .expression: pluginMacroRole = .expression
+  case .declaration: pluginMacroRole = .freeStandingDeclaration
+  case .codeItem: pluginMacroRole = .codeItem
+  }
+
   // Send the message.
   let message = HostToPluginMessage.expandFreestandingMacro(
     macro: .init(moduleName: macro.moduleName, typeName: macro.typeName, name: macroName),
+    macroRole: pluginMacroRole,
     discriminator: discriminator,
     syntax: PluginMessage.Syntax(syntax: Syntax(expansionSyntax), in: sourceFilePtr)!)
   do {
@@ -541,6 +560,7 @@ func expandFreestandingMacroIPC(
 
 func expandFreestandingMacroInProcess(
   macroPtr: UnsafeRawPointer,
+  macroRole: MacroRole,
   diagEnginePtr: UnsafeMutablePointer<UInt8>,
   expansionSyntax: FreestandingMacroExpansionSyntax,
   sourceFilePtr: UnsafePointer<ExportedSourceFile>,
@@ -580,6 +600,7 @@ func expandFreestandingMacroInProcess(
 
   return SwiftSyntaxMacroExpansion.expandFreestandingMacro(
     definition: macro,
+    macroRole: macroRole,
     node: node,
     in: context
   )

lib/ASTGen/Sources/ASTGen/PluginMessages.swift

@@ -20,6 +20,7 @@ internal enum HostToPluginMessage: Codable {
   /// Expand a '@freestanding' macro.
   case expandFreestandingMacro(
     macro: PluginMessage.MacroReference,
+    macroRole: PluginMessage.MacroRole? = nil,
     discriminator: String,
     syntax: PluginMessage.Syntax
   )
@@ -91,6 +92,7 @@ internal enum PluginToHostMessage: Codable {
     case member
     case peer
     case conformance
+    case codeItem
   }
 
   struct SourceLocation: Codable {

lib/IDETool/SyntacticMacroExpansion.cpp

@@ -412,7 +412,7 @@ void SyntacticMacroExpansionInstance::expand(
     SourceFile *SF, const MacroExpansionSpecifier &expansion,
     SourceEditConsumer &consumer) {
 
-  // Find the expansion at 'expantion.offset'.
+  // Find the expansion at 'expansion.offset'.
   MacroExpansionFinder expansionFinder(
       SourceMgr,
       SourceMgr.getLocForOffset(*SF->getBufferID(), expansion.offset));

lib/Sema/TypeCheckMacros.cpp

@@ -66,7 +66,8 @@ extern "C" ptrdiff_t swift_ASTGen_checkMacroDefinition(
 
 extern "C" ptrdiff_t swift_ASTGen_expandFreestandingMacro(
     void *diagEngine, void *macro, uint8_t externalKind,
-    const char *discriminator, ptrdiff_t discriminatorLength, void *sourceFile,
+    const char *discriminator, ptrdiff_t discriminatorLength,
+    uint8_t rawMacroRole, void *sourceFile,
     const void *sourceLocation, const char **evaluatedSource,
     ptrdiff_t *evaluatedSourceLength);
 
@@ -901,6 +902,13 @@ evaluateFreestandingMacro(FreestandingMacroExpansion *expansion,
 #endif
   });
 
+  // Only one freestanding macro role is permitted, so look at the roles to
+  // figure out which one to use.
+  MacroRole macroRole =
+    macroRoles.contains(MacroRole::Expression) ? MacroRole::Expression
+    : macroRoles.contains(MacroRole::Declaration) ? MacroRole::Declaration
+    : MacroRole::CodeItem;
+
   auto macroDef = macro->getDefinition();
   switch (macroDef.kind) {
   case MacroDefinition::Kind::Undefined:
@@ -961,7 +969,8 @@ evaluateFreestandingMacro(FreestandingMacroExpansion *expansion,
     swift_ASTGen_expandFreestandingMacro(
         &ctx.Diags, externalDef->opaqueHandle,
         static_cast<uint32_t>(externalDef->kind), discriminator->data(),
-        discriminator->size(), astGenSourceFile,
+        discriminator->size(),
+        static_cast<uint32_t>(macroRole), astGenSourceFile,
         expansion->getSourceRange().Start.getOpaquePointerValue(),
         &evaluatedSourceAddress, &evaluatedSourceLength);
     if (!evaluatedSourceAddress)

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -73,6 +73,26 @@ public struct StringifyMacro: ExpressionMacro {
   }
 }
 
+public struct ExprAndDeclMacro: ExpressionMacro, DeclarationMacro {
+  public static func expansion(
+    of macro: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    guard let argument = macro.argumentList.first?.expression else {
+      fatalError("boom")
+    }
+
+    return "(\(argument), \(StringLiteralExprSyntax(content: argument.description)))"
+  }
+
+  public static func expansion(
+    of macro: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> [DeclSyntax] {
+    return []
+  }
+}
+
 public struct StringifyAndTryMacro: ExpressionMacro {
   public static func expansion(
     of macro: some FreestandingMacroExpansionSyntax,

test/Macros/macro_expand.swift

@@ -510,3 +510,27 @@ func testHasEqualsSelf(
   _ = (zP == true)
   _ = (wP == true)
 }
+
+// Macro whose implementation is both an expression and declaration macro.
+@freestanding(declaration)
+macro AsDeclMacro<T>(_ value: T) = #externalMacro(module: "MacroDefinition", type: "ExprAndDeclMacro")
+
+@freestanding(expression)
+macro AsExprMacro<T>(_ value: T) -> (T, String) = #externalMacro(module: "MacroDefinition", type: "ExprAndDeclMacro")
+
+func testExpressionAndDeclarationMacro() {
+  #AsExprMacro(1 + 1) // expected-warning{{expression of type '(Int, String)' is unused}}
+  struct Inner {
+    #AsDeclMacro(1 + 1)
+  }
+  #AsDeclMacro(1 + 1)
+}
+
+// Expression macro implementation with declaration macro role
+@freestanding(declaration) macro stringifyAsDeclMacro<T>(_ value: T) = #externalMacro(module: "MacroDefinition", type: "StringifyMacro")
+func testExpressionAsDeclarationMacro() {
+#if TEST_DIAGNOSTICS
+  #stringifyAsDeclMacro(1+1)
+  // expected-error@-1{{macro implementation type 'StringifyMacro' doesn't conform to required protocol 'DeclarationMacro' (from macro 'stringifyAsDeclMacro')}}
+#endif
+}

test/Macros/macro_plugin_basic.swift

@@ -23,9 +23,9 @@
 
 // CHECK: ->(plugin:[[#PID:]]) {"getCapability":{}}
 // CHECK: <-(plugin:[[#PID]]) {"getCapabilityResult":{"capability":{"protocolVersion":1}}}
-// CHECK: ->(plugin:[[#PID]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"testString","typeName":"TestStringMacro"},"syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":5,"offset":301},"source":"#testString(123)"}}}
+// CHECK: ->(plugin:[[#PID]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"testString","typeName":"TestStringMacro"},"macroRole":"expression","syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":5,"offset":301},"source":"#testString(123)"}}}
 // CHECK: <-(plugin:[[#PID]]) {"expandFreestandingMacroResult":{"diagnostics":[],"expandedSource":"\"123\"\n  +   \"foo  \""}}
-// CHECK: ->(plugin:[[#PID]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"testStringWithError","typeName":"TestStringWithErrorMacro"},"syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":6,"offset":336},"source":"#testStringWithError(321)"}}}
+// CHECK: ->(plugin:[[#PID]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"testStringWithError","typeName":"TestStringWithErrorMacro"},"macroRole":"expression","syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":6,"offset":336},"source":"#testStringWithError(321)"}}}
 // CHECK: <-(plugin:[[#PID]]) {"expandFreestandingMacroResult":{"diagnostics":[{"fixIts":[],"highlights":[],"message":"message from plugin","notes":[],"position":{"fileName":"BUILD_DIR{{.*}}test.swift","offset":336},"severity":"error"}],"expandedSource":"\"bar\""}}
 
 //--- test.swift

test/Macros/macro_plugin_error.swift

@@ -23,12 +23,12 @@
 
 // CHECK: ->(plugin:[[#PID1:]]) {"getCapability":{}}
 // CHECK-NEXT: <-(plugin:[[#PID1]]) {"getCapabilityResult":{"capability":{"protocolVersion":1}}}
-// CHECK-NEXT: ->(plugin:[[#PID1]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"fooMacro","typeName":"FooMacro"},"syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":6,"offset":[[#]]},"source":"#fooMacro(1)"}}}
+// CHECK-NEXT: ->(plugin:[[#PID1]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"fooMacro","typeName":"FooMacro"},"macroRole":"expression","syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":6,"offset":[[#]]},"source":"#fooMacro(1)"}}}
 // CHECK-NEXT: <-(plugin:[[#PID1]]) {"invalidResponse":{}}
-// CHECK-NEXT: ->(plugin:[[#PID1]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"fooMacro","typeName":"FooMacro"},"syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":8,"offset":[[#]]},"source":"#fooMacro(2)"}}}
+// CHECK-NEXT: ->(plugin:[[#PID1]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"fooMacro","typeName":"FooMacro"},"macroRole":"expression","syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":8,"offset":[[#]]},"source":"#fooMacro(2)"}}}
 // ^ This messages causes the mock plugin exit because there's no matching expected message.
 
-// CHECK: ->(plugin:[[#PID2:]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"fooMacro","typeName":"FooMacro"},"syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":10,"offset":[[#]]},"source":"#fooMacro(3)"}}}
+// CHECK: ->(plugin:[[#PID2:]]) {"expandFreestandingMacro":{"discriminator":"$s{{.+}}","macro":{"moduleName":"TestPlugin","name":"fooMacro","typeName":"FooMacro"},"macroRole":"expression","syntax":{"kind":"expression","location":{"column":19,"fileID":"MyApp/test.swift","fileName":"BUILD_DIR{{.+}}test.swift","line":10,"offset":[[#]]},"source":"#fooMacro(3)"}}}
 // CHECK-NEXT: <-(plugin:[[#PID2:]]) {"expandFreestandingMacroResult":{"diagnostics":[],"expandedSource":"3.description"}}
 
 //--- test.swift

test/Macros/macro_plugin_server.swift

@@ -37,16 +37,16 @@
 // CHECK-NEXT: <-(plugin:[[#PID1]]) {"loadPluginLibraryResult":{"diagnostics":[],"loaded":true}}
 // CHECK-NEXT: ->(plugin:[[#PID1]]) {"loadPluginLibrary":{"libraryPath":"BUILD_DIR{{.*}}plugins/libEvilMacros.dylib","moduleName":"EvilMacros"}}
 // CHECK-NEXT: <-(plugin:[[#PID1]]) {"loadPluginLibraryResult":{"diagnostics":[],"loaded":true}}
-// CHECK-NEXT: ->(plugin:[[#PID1]]) {"expandFreestandingMacro":{"discriminator":"${{.*}}","macro":{"moduleName":"MacroDefinition","name":"stringify","typeName":"StringifyMacro"},"syntax":{"kind":"expression","location":{{{.+}}},"source":"#stringify(a + b)"}}}
+// CHECK-NEXT: ->(plugin:[[#PID1]]) {"expandFreestandingMacro":{"discriminator":"${{.*}}","macro":{"moduleName":"MacroDefinition","name":"stringify","typeName":"StringifyMacro"},"macroRole":"expression","syntax":{"kind":"expression","location":{{{.+}}},"source":"#stringify(a + b)"}}}
 // CHECK-NEXT: <-(plugin:[[#PID1]]) {"expandFreestandingMacroResult":{"diagnostics":[],"expandedSource":"(a + b, \"a + b\")"}}
-// CHECK-NEXT: ->(plugin:[[#PID1]]) {"expandFreestandingMacro":{"discriminator":"${{.*}}","macro":{"moduleName":"EvilMacros","name":"evil","typeName":"CrashingMacro"},"syntax":{"kind":"expression","location":{{{.+}}},"source":"#evil(42)"}}}
+// CHECK-NEXT: ->(plugin:[[#PID1]]) {"expandFreestandingMacro":{"discriminator":"${{.*}}","macro":{"moduleName":"EvilMacros","name":"evil","typeName":"CrashingMacro"},"macroRole":"expression","syntax":{"kind":"expression","location":{{{.+}}},"source":"#evil(42)"}}}
 // ^ This crashes the plugin server.
 
 // CHECK-NEXT: ->(plugin:[[#PID2:]]) {"loadPluginLibrary":{"libraryPath":"BUILD_DIR{{.*}}plugins/libMacroDefinition.dylib","moduleName":"MacroDefinition"}}
 // CHECK-NEXT: <-(plugin:[[#PID2]]) {"loadPluginLibraryResult":{"diagnostics":[],"loaded":true}}
 // CHECK-NEXT: ->(plugin:[[#PID2]]) {"loadPluginLibrary":{"libraryPath":"BUILD_DIR{{.*}}plugins/libEvilMacros.dylib","moduleName":"EvilMacros"}}
 // CHECK-NEXT: <-(plugin:[[#PID2]]) {"loadPluginLibraryResult":{"diagnostics":[],"loaded":true}}
-// CHECK-NEXT: ->(plugin:[[#PID2]]) {"expandFreestandingMacro":{"discriminator":"${{.*}}","macro":{"moduleName":"MacroDefinition","name":"stringify","typeName":"StringifyMacro"},"syntax":{"kind":"expression","location":{{{.+}}},"source":"#stringify(b + a)"}}}
+// CHECK-NEXT: ->(plugin:[[#PID2]]) {"expandFreestandingMacro":{"discriminator":"${{.*}}","macro":{"moduleName":"MacroDefinition","name":"stringify","typeName":"StringifyMacro"},"macroRole":"expression","syntax":{"kind":"expression","location":{{{.+}}},"source":"#stringify(b + a)"}}}
 // CHECK-NEXT: <-(plugin:[[#PID2]]) {"expandFreestandingMacroResult":{"diagnostics":[],"expandedSource":"(b + a, \"b + a\")"}}
 
 @freestanding(expression) macro stringify<T>(_ value: T) -> (T, String) = #externalMacro(module: "MacroDefinition", type: "StringifyMacro")