[Macros] Remove the source location converter from MacroEvaluationContext.

Having the source location converter in the context exposes the entire
contents of the source file containing the macro expansion to the
implementation of the macro. While convenient for the macro author,
this breaks Swift's incremental build model, because Swift assumes
that (e.g.) changing the body of a function cannot affect the result of
type-checking the body of an unrelated function.

Drop the implementations of some "built-in" macros that are no longer
expressible, such as `#filePath`, `#line`, and `#column`.

Author: DougGregor

Sources/_SwiftSyntaxMacros/MacroEvaluationContext.swift

@@ -18,14 +18,29 @@ public struct MacroEvaluationContext {
   /// The name of the module in which the macro is being evaluated.
   public let moduleName: String
 
-  /// Used to map the provided syntax nodes into source locations.
-  public let sourceLocationConverter: SourceLocationConverter
+  /// The name of the source file in which the macro is being evaluated,
+  /// without any path information.
+  ///
+  /// Swift prevents two files within the same module from having the same
+  /// name, so the combination of file and module name is unique.
+  public let fileName: String
 
+  /// Create a new macro evaluation context.
+  public init(moduleName: String, fileName: String) {
+    self.moduleName = moduleName
+    self.fileName = fileName
+  }
+
+  /// Create a new macro evaluation context.
+  @available(*, deprecated, message: "Use init(moduleName:fileName:)")
   public init(
     moduleName: String,
     sourceLocationConverter: SourceLocationConverter
   ) {
-    self.moduleName = moduleName
-    self.sourceLocationConverter = sourceLocationConverter
+    let fileName = sourceLocationConverter.location(
+      for: AbsolutePosition(utf8Offset: -1)
+    ).file ?? "unknown.swift"
+
+    self.init(moduleName: moduleName, fileName: fileName)
   }
 }

Sources/_SwiftSyntaxMacros/MacroSystem+Builtin.swift

@@ -13,28 +13,6 @@
 import SwiftSyntax
 import SwiftSyntaxBuilder
 
-public struct ColumnMacro: ExpressionMacro {
-  public static func apply(
-    _ macro: MacroExpansionExprSyntax, in context: MacroEvaluationContext
-  ) -> MacroResult<ExprSyntax> {
-    let line = macro.startLocation(
-      converter: context.sourceLocationConverter
-    ).column ?? 0
-    return .init("\(literal: line)")
-  }
-}
-
-public struct LineMacro: ExpressionMacro {
-  public static func apply(
-    _ macro: MacroExpansionExprSyntax, in context: MacroEvaluationContext
-  ) -> MacroResult<ExprSyntax> {
-    let line = macro.startLocation(
-      converter: context.sourceLocationConverter
-    ).line ?? 0
-    return .init("\(literal: line)")
-  }
-}
-
 extension PatternBindingSyntax {
   /// When the variable is declaring a single binding, produce the name of
   /// that binding.
@@ -208,37 +186,12 @@ public struct ImageLiteralMacro: ExpressionMacro {
   }
 }
 
-public struct FilePathMacro: ExpressionMacro {
-  public static func apply(
-    _ macro: MacroExpansionExprSyntax, in context: MacroEvaluationContext
-  ) -> MacroResult<ExprSyntax> {
-    let fileName = context.sourceLocationConverter.location(
-      for: .init(utf8Offset: 0)
-    ).file ?? "<unknown file>"
-    let fileLiteral: ExprSyntax = "\(literal: fileName)"
-    if let leadingTrivia = macro.leadingTrivia {
-      return MacroResult(fileLiteral.withLeadingTrivia(leadingTrivia))
-    }
-    return MacroResult(fileLiteral)
-  }
-}
-
 public struct FileIDMacro: ExpressionMacro {
   public static func apply(
     _ macro: MacroExpansionExprSyntax, in context: MacroEvaluationContext
   ) -> MacroResult<ExprSyntax> {
-    var fileName = context.sourceLocationConverter.location(
-      for: .init(utf8Offset: 0)
-    ).file ?? "<unknown file>"
-
-    // Only keep everything after the last slash.
-    if let lastSlash = fileName.lastIndex(of: "/") {
-      fileName = String(fileName[fileName.index(after: lastSlash)...])
-    }
-
     // FIXME: Compiler has more sophisticated file ID computation
-    let fileID = "\(context.moduleName)/\(fileName)"
-
+    let fileID = "\(context.moduleName)/\(context.fileName)"
     let fileLiteral: ExprSyntax = "\(literal: fileID)"
     if let leadingTrivia = macro.leadingTrivia {
       return MacroResult(fileLiteral.withLeadingTrivia(leadingTrivia))
@@ -251,13 +204,9 @@ extension MacroSystem {
   public static var builtinMacroSystem: MacroSystem = {
     var macroSystem = MacroSystem()
     try! macroSystem.add(ColorLiteralMacro.self, name: "colorLiteral")
-    try! macroSystem.add(ColumnMacro.self, name: "column")
     try! macroSystem.add(FileIDMacro.self, name: "fileID")
-    try! macroSystem.add(FileLiteralMacro.self, name: "file")
-    try! macroSystem.add(FilePathMacro.self, name: "filePath")
     try! macroSystem.add(FunctionMacro.self, name: "function")
     try! macroSystem.add(ImageLiteralMacro.self, name: "imageLiteral")
-    try! macroSystem.add(LineMacro.self, name: "line")
     return macroSystem
   }()
 }

Sources/swift-parser-cli/swift-parser-cli.swift

@@ -48,6 +48,18 @@ private func getContentsOfSourceFile(at path: String?) throws -> [UInt8] {
   return [UInt8](source)
 }
 
+extension String {
+  /// Drop everything up to and including the last '/' from the string.
+  fileprivate func withoutPath() -> String {
+    // Only keep everything after the last slash.
+    if let lastSlash = lastIndex(of: "/") {
+      return String(self[index(after: lastSlash)...])
+    }
+
+    return self
+  }
+}
+
 /// Fold all of the sequences in the given source file.
 func foldAllSequences(_ tree: SourceFileSyntax) -> (Syntax, [Diagnostic]) {
   var diags: [Diagnostic] = []
@@ -230,9 +242,8 @@ class ExpandMacros: ParsableCommand {
         resultTree = Syntax(tree)
       }
 
-      let converter = SourceLocationConverter(file: self.sourceFile, tree: resultTree)
       let context = MacroEvaluationContext(
-        moduleName: "MyModule", sourceLocationConverter: converter
+        moduleName: "MyModule", fileName: self.sourceFile.withoutPath()
       )
       var diags = ParseDiagnosticsGenerator.diagnostics(for: tree)
       let transformedTree = MacroSystem.exampleSystem.evaluateMacros(

Tests/SwiftSyntaxMacrosTest/MacroSystemTests.swift

@@ -20,27 +20,20 @@ final class MacroSystemTests: XCTestCase {
   func testExpressionExpansion() {
     let sf: SourceFileSyntax =
       """
-      #line
-      let a = (#line)
       let b = #stringify(x + y)
       #colorLiteral(red: 0.5, green: 0.5, blue: 0.25, alpha: 1.0)
-      let c = #column
       """
-    let converter = SourceLocationConverter(file: "test.swift", tree: sf)
     let context = MacroEvaluationContext(
-      moduleName: "MyModule", sourceLocationConverter: converter
+      moduleName: "MyModule", fileName: "test.swift"
     )
     let transformedSF = MacroSystem.exampleSystem.evaluateMacros(
       node: sf, in: context, errorHandler: { error in }
     )
     AssertStringsEqualWithDiff(
       transformedSF.description,
       """
-      1
-      let a = (2)
       let b = (x + y, "x + y")
       .init(_colorLiteralRed: 0.5, green: 0.5, blue: 0.25, alpha: 1.0)
-      let c = 9
       """
     )
   }
@@ -53,9 +46,8 @@ final class MacroSystemTests: XCTestCase {
         return true
       })
       """
-    let converter = SourceLocationConverter(file: "test.swift", tree: sf)
     let context = MacroEvaluationContext(
-      moduleName: "MyModule", sourceLocationConverter: converter
+      moduleName: "MyModule", fileName: "test.swift"
     )
     let transformedSF = MacroSystem.exampleSystem.evaluateMacros(
       node: sf, in: context, errorHandler: { error in }
@@ -102,9 +94,8 @@ final class MacroSystemTests: XCTestCase {
         static var staticProp: String = #function
       }
       """
-    let converter = SourceLocationConverter(file: "test.swift", tree: sf)
     let context = MacroEvaluationContext(
-      moduleName: "MyModule", sourceLocationConverter: converter
+      moduleName: "MyModule", fileName: "test.swift"
     )
     let transformedSF = MacroSystem.exampleSystem.evaluateMacros(
       node: sf, in: context, errorHandler: { error in }
@@ -146,22 +137,17 @@ final class MacroSystemTests: XCTestCase {
   func testFileExpansions() {
     let sf: SourceFileSyntax =
       """
-      let a = #filePath
       let b = #fileID
       """
-    let converter = SourceLocationConverter(
-      file: "/tmp/src/taylor.swift", tree: sf
-    )
     let context = MacroEvaluationContext(
-      moduleName: "MyModule", sourceLocationConverter: converter
+      moduleName: "MyModule", fileName: "taylor.swift"
     )
     let transformedSF = MacroSystem.exampleSystem.evaluateMacros(
       node: sf, in: context, errorHandler: { error in }
     )
     AssertStringsEqualWithDiff(
       transformedSF.description,
       """
-      let a = "/tmp/src/taylor.swift"
       let b = "MyModule/taylor.swift"
       """
     )