[Macros] Fix column calculation in MacroExpansionContext for plugins

When retriving a location for a node at the first line, column
calculation was incorrect. 'column' of 'PluginMessage.Syntax' is
1-based, so we need to '-1' when using it as a offset.

Author: rintaro

Examples/Sources/MacroExamples/Implementation/Expression/SourceLocationMacro.swift

@@ -0,0 +1,54 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+import SwiftSyntaxMacros
+
+public struct NativeFileIDMacro: ExpressionMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    return context.location(
+        of: node, at: .afterLeadingTrivia, filePathMode: .fileID
+    )!.file
+  }
+}
+
+public struct NativeFilePathMacro: ExpressionMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    return context.location(
+        of: node, at: .afterLeadingTrivia, filePathMode: .filePath
+    )!.file
+  }
+}
+
+public struct NativeLineMacro: ExpressionMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    return context.location(of: node)!.line
+  }
+}
+
+public struct NativeColumnMacro: ExpressionMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    return context.location(of: node)!.column
+  }
+}

Examples/Sources/MacroExamples/Implementation/Plugin.swift

@@ -32,6 +32,10 @@ struct MyPlugin: CompilerPlugin {
     FuncUniqueMacro.self,
     MemberDeprecatedMacro.self,
     MetaEnumMacro.self,
+    NativeColumnMacro.self,
+    NativeFileIDMacro.self,
+    NativeFilePathMacro.self,
+    NativeLineMacro.self,
     NewTypeMacro.self,
     ObservableMacro.self,
     ObservablePropertyMacro.self,

Examples/Sources/MacroExamples/Interface/SourceLocationMacros.swift

@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+@freestanding(expression)
+public macro FileID<T: ExpressibleByStringLiteral>() -> T = #externalMacro(
+    module: "MacroExamplesImplementation", type: "NativeFileIDMacro"
+)
+
+
+@freestanding(expression)
+public macro FilePath<T: ExpressibleByStringLiteral>() -> T = #externalMacro(
+    module: "MacroExamplesImplementation", type: "NativeFilePathMacro"
+)
+
+@freestanding(expression)
+public macro Line<T : ExpressibleByIntegerLiteral>() -> T = #externalMacro(
+    module: "MacroExamplesImplementation", type: "NativeLineMacro"
+)
+
+@freestanding(expression)
+public macro Column<T : ExpressibleByIntegerLiteral>() -> T = #externalMacro(
+    module: "MacroExamplesImplementation", type: "NativeColumnMacro"
+)

Examples/Sources/MacroExamples/Playground/SourceLocationMacrosPlayground.swift

@@ -0,0 +1,8 @@
+import MacroExamplesInterface
+
+func runSourceLoctionMacrosPlayground() {
+  print("FileID: \(#FileID as String)")
+  print("FilePath: \(#FilePath as String)")
+  print("Line: \(#Line as Int)")
+  print("Column: \(#Column as Int)")
+}

Examples/Sources/MacroExamples/Playground/main.swift

@@ -55,3 +55,7 @@ runPeerMacrosPlayground()
 runEnvironmentValueAccessorMacroPlayground()
 
 #endif
+
+// MARK: - SourceLocationMacros
+
+runSourceLoctionMacrosPlayground()

Sources/SwiftCompilerPluginMessageHandling/PluginMacroExpansionContext.swift

@@ -174,8 +174,9 @@ class SourceManager {
     let localLocation = base.locationConverter.location(for: localPosition)
 
     let positionOffset = base.location.offset
+    // NOTE '- 1' because base.location.{line|column} are 1-based.
     let lineOffset = base.location.line - 1
-    let columnOffset = localLocation.line == 1 ? base.location.column : 0
+    let columnOffset = localLocation.line == 1 ? (base.location.column - 1) : 0
 
     return SourceLocation(
       // NOTE: IUO because 'localLocation' is created by a location converter