Merge pull request swiftlang#1471 from DougGregor/macro-context-add-diags-5.9

Author: DougGregor

Sources/SwiftCompilerPluginMessageHandling/Macros.swift

@@ -62,14 +62,8 @@ extension CompilerPluginMessageHandler {
         throw MacroExpansionError.unmathedMacroRole
       }
     } catch {
-      let diagMessage: DiagnosticMessage
-      if let message = error as? DiagnosticMessage, message.severity == .error {
-        diagMessage = message
-      } else {
-        diagMessage = ThrownErrorDiagnostic(message: String(describing: error))
-      }
+      context.addDiagnostics(from: error, node: syntax)
       expandedSource = ""
-      context.diagnose(Diagnostic(node: syntax, message: diagMessage))
     }
 
     let diagnostics = context.diagnostics.map {
@@ -221,14 +215,8 @@ extension CompilerPluginMessageHandler {
         throw MacroExpansionError.unmathedMacroRole
       }
     } catch {
-      let diagMessage: DiagnosticMessage
-      if let message = error as? DiagnosticMessage, message.severity == .error {
-        diagMessage = message
-      } else {
-        diagMessage = ThrownErrorDiagnostic(message: String(describing: error))
-      }
+      context.addDiagnostics(from: error, node: attributeNode)
       expandedSources = []
-      context.diagnose(Diagnostic(node: Syntax(attributeNode), message: diagMessage))
     }
 
     let diagnostics = context.diagnostics.map {
@@ -239,14 +227,3 @@ extension CompilerPluginMessageHandler {
     )
   }
 }
-
-/// Diagnostic message used for thrown errors.
-fileprivate struct ThrownErrorDiagnostic: DiagnosticMessage {
-  let message: String
-
-  var severity: DiagnosticSeverity { .error }
-
-  var diagnosticID: MessageID {
-    .init(domain: "SwiftSyntaxMacros", id: "ThrownErrorDiagnostic")
-  }
-}

Sources/SwiftSyntaxMacros/MacroExpansionContext.swift

@@ -189,22 +189,23 @@ private struct ThrownErrorDiagnostic: DiagnosticMessage {
 extension MacroExpansionContext {
   /// Add diagnostics from the error thrown during macro expansion.
   public func addDiagnostics<S: SyntaxProtocol>(from error: Error, node: S) {
-    guard let diagnosticsError = error as? DiagnosticsError else {
-      diagnose(
-        Diagnostic(
-          node: Syntax(node),
-          message: ThrownErrorDiagnostic(message: String(describing: error))
-        )
-      )
-      return
+    // Inspect the error to form an appropriate set of diagnostics.
+    var diagnostics: [Diagnostic]
+    if let diagnosticsError = error as? DiagnosticsError {
+      diagnostics = diagnosticsError.diagnostics
+    } else if let message = error as? DiagnosticMessage {
+      diagnostics = [Diagnostic(node: Syntax(node), message: message)]
+    } else {
+      diagnostics = [Diagnostic(node: Syntax(node), message: ThrownErrorDiagnostic(message: String(describing: error)))]
     }
 
-    for diagnostic in diagnosticsError.diagnostics {
+    // Emit the diagnostics.
+    for diagnostic in diagnostics {
       diagnose(diagnostic)
     }
 
-    // handle possibility that none of the diagnostics was an error
-    if !diagnosticsError.diagnostics.contains(
+    // Handle possibility that none of the diagnostics was an error.
+    if !diagnostics.contains(
       where: { $0.diagMessage.severity == .error }
     ) {
       diagnose(

Sources/SwiftSyntaxMacros/MacroReplacement.swift

@@ -14,7 +14,7 @@ enum MacroExpanderError: DiagnosticMessage {
       return "macro expansion requires a definition"
 
     case .definitionNotMacroExpansion:
-      return "macro definition must itself by a macro expansion expression (starting with '#')"
+      return "macro must itself be defined by a macro expansion expression (starting with '#')"
 
     case .nonParameterReference(let name):
       return "reference to value '\(name.text)' that is not a macro parameter in expansion"