Syntactic macro system

CodeGeneration/Sources/SyntaxSupport/gyb_generated/DeclNodes.swift

@@ -1500,4 +1500,43 @@ public let DECL_NODES: [Node] = [
                ])
        ]),
 
+  Node(name: "MacroExpansionDecl",
+       nameForDiagnostics: "pound literal declaration",
+       kind: "Decl",
+       children: [
+         Child(name: "PoundToken",
+               kind: "PoundToken",
+               description: "The `#` sign.",
+               tokenChoices: [
+                 "Pound"
+               ]),
+         Child(name: "Macro",
+               kind: "IdentifierToken",
+               tokenChoices: [
+                 "Identifier"
+               ]),
+         Child(name: "LeftParen",
+               kind: "LeftParenToken",
+               isOptional: true,
+               tokenChoices: [
+                 "LeftParen"
+               ]),
+         Child(name: "ArgumentList",
+               kind: "TupleExprElementList",
+               collectionElementName: "Argument"),
+         Child(name: "RightParen",
+               kind: "RightParenToken",
+               isOptional: true,
+               tokenChoices: [
+                 "RightParen"
+               ]),
+         Child(name: "TrailingClosure",
+               kind: "ClosureExpr",
+               isOptional: true),
+         Child(name: "AdditionalTrailingClosures",
+               kind: "MultipleTrailingClosureElementList",
+               isOptional: true,
+               collectionElementName: "AdditionalTrailingClosure")
+       ]),
+
 ]

CodeGeneration/Sources/SyntaxSupport/gyb_generated/ExprNodes.swift

@@ -1288,6 +1288,45 @@ public let EXPR_NODES: [Node] = [
                ])
        ]),
 
+  Node(name: "MacroExpansionExpr",
+       nameForDiagnostics: "pound literal expression",
+       kind: "Expr",
+       children: [
+         Child(name: "PoundToken",
+               kind: "PoundToken",
+               description: "The `#` sign.",
+               tokenChoices: [
+                 "Pound"
+               ]),
+         Child(name: "Macro",
+               kind: "IdentifierToken",
+               tokenChoices: [
+                 "Identifier"
+               ]),
+         Child(name: "LeftParen",
+               kind: "LeftParenToken",
+               isOptional: true,
+               tokenChoices: [
+                 "LeftParen"
+               ]),
+         Child(name: "ArgumentList",
+               kind: "TupleExprElementList",
+               collectionElementName: "Argument"),
+         Child(name: "RightParen",
+               kind: "RightParenToken",
+               isOptional: true,
+               tokenChoices: [
+                 "RightParen"
+               ]),
+         Child(name: "TrailingClosure",
+               kind: "ClosureExpr",
+               isOptional: true),
+         Child(name: "AdditionalTrailingClosures",
+               kind: "MultipleTrailingClosureElementList",
+               isOptional: true,
+               collectionElementName: "AdditionalTrailingClosure")
+       ]),
+
   Node(name: "PostfixIfConfigExpr",
        nameForDiagnostics: nil,
        kind: "Expr",

CodeGeneration/Sources/SyntaxSupport/gyb_generated/NodeSerializationCodes.swift

@@ -296,4 +296,6 @@ public let SYNTAX_NODE_SERIALIZATION_CODES: [String: Int] = [
   "KeyPathComponentList": 285,
   "KeyPathComponent": 286,
   "OldKeyPathExpr": 287,
+  "MacroExpansionExpr": 288,
+  "MacroExpansionDecl": 289,
 ]

Package.swift

@@ -50,6 +50,7 @@ let package = Package(
     .library(name: "SwiftSyntax", type: .static, targets: ["SwiftSyntax"]),
     .library(name: "SwiftSyntaxParser", type: .static, targets: ["SwiftSyntaxParser"]),
     .library(name: "SwiftSyntaxBuilder", type: .static, targets: ["SwiftSyntaxBuilder"]),
+    .library(name: "_SwiftSyntaxMacros", type: .static, targets: ["_SwiftSyntaxMacros"]),
   ],
   targets: [
     .target(
@@ -140,13 +141,21 @@ let package = Package(
         "SwiftCompilerSupport.h"
       ]
     ),
+    .target(
+      name: "_SwiftSyntaxMacros",
+      dependencies: [
+        "SwiftSyntax", "SwiftSyntaxBuilder", "SwiftParser", "SwiftDiagnostics"
+      ],
+      exclude: [
+        "CMakeLists.txt",
+      ]),
     .executableTarget(
       name: "lit-test-helper",
       dependencies: ["SwiftSyntax", "SwiftSyntaxParser"]
     ),
     .executableTarget(
       name: "swift-parser-cli",
-      dependencies: ["SwiftDiagnostics", "SwiftSyntax", "SwiftParser", "SwiftOperators",
+      dependencies: ["SwiftDiagnostics", "SwiftSyntax", "SwiftParser", "SwiftOperators", "_SwiftSyntaxMacros",
                      .product(name: "ArgumentParser", package: "swift-argument-parser")]
     ),
     .testTarget(
@@ -166,6 +175,12 @@ let package = Package(
       dependencies: ["SwiftSyntaxParser", "_SwiftSyntaxTestSupport"],
       exclude: ["Inputs"]
     ),
+    .testTarget(
+      name: "SwiftSyntaxMacrosTest",
+      dependencies: ["SwiftDiagnostics", "SwiftOperators", "SwiftParser",
+                     "_SwiftSyntaxTestSupport", "SwiftSyntaxBuilder",
+                     "_SwiftSyntaxMacros"]
+    ),
     .testTarget(
       name: "PerformanceTest",
       dependencies: ["SwiftSyntax", "SwiftSyntaxParser", "SwiftParser"],

Sources/SwiftBasicFormat/generated/BasicFormat.swift

@@ -806,6 +806,24 @@ open class BasicFormat: SyntaxRewriter {
     return ExprSyntax(ObjcSelectorExprSyntax(unexpectedBeforePoundSelector, poundSelector: poundSelector, unexpectedBetweenPoundSelectorAndLeftParen, leftParen: leftParen, unexpectedBetweenLeftParenAndKind, kind: kind, unexpectedBetweenKindAndColon, colon: colon, unexpectedBetweenColonAndName, name: name, unexpectedBetweenNameAndRightParen, rightParen: rightParen))
   }
 
+  open override func visit(_ node: MacroExpansionExprSyntax) -> ExprSyntax {
+    let unexpectedBeforePoundToken = node.unexpectedBeforePoundToken.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let poundToken = self.visit(node.poundToken).cast(TokenSyntax.self)
+    let unexpectedBetweenPoundTokenAndMacro = node.unexpectedBetweenPoundTokenAndMacro.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let macro = self.visit(node.macro).cast(TokenSyntax.self)
+    let unexpectedBetweenMacroAndLeftParen = node.unexpectedBetweenMacroAndLeftParen.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let leftParen = node.leftParen.map(self.visit)?.cast(TokenSyntax.self)
+    let unexpectedBetweenLeftParenAndArgumentList = node.unexpectedBetweenLeftParenAndArgumentList.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let argumentList = self.visit(node.argumentList).cast(TupleExprElementListSyntax.self)
+    let unexpectedBetweenArgumentListAndRightParen = node.unexpectedBetweenArgumentListAndRightParen.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let rightParen = node.rightParen.map(self.visit)?.cast(TokenSyntax.self)
+    let unexpectedBetweenRightParenAndTrailingClosure = node.unexpectedBetweenRightParenAndTrailingClosure.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let trailingClosure = node.trailingClosure.map(self.visit)?.cast(ClosureExprSyntax.self)
+    let unexpectedBetweenTrailingClosureAndAdditionalTrailingClosures = node.unexpectedBetweenTrailingClosureAndAdditionalTrailingClosures.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let additionalTrailingClosures = node.additionalTrailingClosures.map(self.visit)?.cast(MultipleTrailingClosureElementListSyntax.self)
+    return ExprSyntax(MacroExpansionExprSyntax(unexpectedBeforePoundToken, poundToken: poundToken, unexpectedBetweenPoundTokenAndMacro, macro: macro, unexpectedBetweenMacroAndLeftParen, leftParen: leftParen, unexpectedBetweenLeftParenAndArgumentList, argumentList: argumentList, unexpectedBetweenArgumentListAndRightParen, rightParen: rightParen, unexpectedBetweenRightParenAndTrailingClosure, trailingClosure: trailingClosure, unexpectedBetweenTrailingClosureAndAdditionalTrailingClosures, additionalTrailingClosures: additionalTrailingClosures))
+  }
+
   open override func visit(_ node: PostfixIfConfigExprSyntax) -> ExprSyntax {
     let unexpectedBeforeBase = node.unexpectedBeforeBase.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
     let base = node.base.map(self.visit)?.cast(ExprSyntax.self)
@@ -1575,6 +1593,24 @@ open class BasicFormat: SyntaxRewriter {
     return Syntax(PrecedenceGroupAssociativitySyntax(unexpectedBeforeAssociativityKeyword, associativityKeyword: associativityKeyword, unexpectedBetweenAssociativityKeywordAndColon, colon: colon, unexpectedBetweenColonAndValue, value: value))
   }
 
+  open override func visit(_ node: MacroExpansionDeclSyntax) -> DeclSyntax {
+    let unexpectedBeforePoundToken = node.unexpectedBeforePoundToken.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let poundToken = self.visit(node.poundToken).cast(TokenSyntax.self)
+    let unexpectedBetweenPoundTokenAndMacro = node.unexpectedBetweenPoundTokenAndMacro.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let macro = self.visit(node.macro).cast(TokenSyntax.self)
+    let unexpectedBetweenMacroAndLeftParen = node.unexpectedBetweenMacroAndLeftParen.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let leftParen = node.leftParen.map(self.visit)?.cast(TokenSyntax.self)
+    let unexpectedBetweenLeftParenAndArgumentList = node.unexpectedBetweenLeftParenAndArgumentList.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let argumentList = self.visit(node.argumentList).cast(TupleExprElementListSyntax.self)
+    let unexpectedBetweenArgumentListAndRightParen = node.unexpectedBetweenArgumentListAndRightParen.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let rightParen = node.rightParen.map(self.visit)?.cast(TokenSyntax.self)
+    let unexpectedBetweenRightParenAndTrailingClosure = node.unexpectedBetweenRightParenAndTrailingClosure.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let trailingClosure = node.trailingClosure.map(self.visit)?.cast(ClosureExprSyntax.self)
+    let unexpectedBetweenTrailingClosureAndAdditionalTrailingClosures = node.unexpectedBetweenTrailingClosureAndAdditionalTrailingClosures.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
+    let additionalTrailingClosures = node.additionalTrailingClosures.map(self.visit)?.cast(MultipleTrailingClosureElementListSyntax.self)
+    return DeclSyntax(MacroExpansionDeclSyntax(unexpectedBeforePoundToken, poundToken: poundToken, unexpectedBetweenPoundTokenAndMacro, macro: macro, unexpectedBetweenMacroAndLeftParen, leftParen: leftParen, unexpectedBetweenLeftParenAndArgumentList, argumentList: argumentList, unexpectedBetweenArgumentListAndRightParen, rightParen: rightParen, unexpectedBetweenRightParenAndTrailingClosure, trailingClosure: trailingClosure, unexpectedBetweenTrailingClosureAndAdditionalTrailingClosures, additionalTrailingClosures: additionalTrailingClosures))
+  }
+
   open override func visit(_ node: TokenListSyntax) -> Syntax {
     let formattedChildren = node.children(viewMode: .all).map {
       self.visit($0).cast(TokenSyntax.self)

Sources/SwiftParser/Declarations.swift

@@ -169,6 +169,8 @@ extension Parser {
       return RawDeclSyntax(directive)
     case (.poundWarningKeyword, _)?, (.poundErrorKeyword, _)?:
       return self.parsePoundDiagnosticDeclaration()
+    case (.pound, _)?:
+      return RawDeclSyntax(self.parseMacroExpansionDeclaration())
     case nil:
       break
     }
@@ -2336,4 +2338,57 @@ extension Parser {
         arena: self.arena))
     }
   }
+
+  /// Parse a macro expansion as an declaration.
+  ///
+  ///
+  /// Grammar
+  /// =======
+  ///
+  /// macro-expansion-declaration → '#' identifier expr-call-suffix?
+  mutating func parseMacroExpansionDeclaration() -> RawMacroExpansionDeclSyntax {
+    let poundKeyword = self.consumeAnyToken()
+    let (unexpectedBeforeMacro, macro) = self.expectIdentifier()
+
+    // Parse the optional parenthesized argument list.
+    let leftParen = self.consume(if: .leftParen, where: { !$0.isAtStartOfLine })
+    let args: [RawTupleExprElementSyntax]
+    let unexpectedBeforeRightParen: RawUnexpectedNodesSyntax?
+    let rightParen: RawTokenSyntax?
+    if leftParen != nil {
+      args = parseArgumentListElements(pattern: .none)
+      (unexpectedBeforeRightParen, rightParen) = self.expect(.rightParen)
+    } else {
+      args = []
+      unexpectedBeforeRightParen = nil
+      rightParen = nil
+    }
+
+    // Parse the optional trailing closures.
+    let trailingClosure: RawClosureExprSyntax?
+    let additionalTrailingClosures: RawMultipleTrailingClosureElementListSyntax?
+    if self.at(.leftBrace),
+       self.lookahead().isValidTrailingClosure(.trailingClosure) {
+      (trailingClosure, additionalTrailingClosures) =
+        self.parseTrailingClosures(.trailingClosure)
+    } else {
+      trailingClosure = nil
+      additionalTrailingClosures = nil
+    }
+
+    return RawMacroExpansionDeclSyntax(
+      poundToken: poundKeyword,
+      unexpectedBeforeMacro,
+      macro: macro,
+      leftParen: leftParen,
+      argumentList: RawTupleExprElementListSyntax(
+        elements: args, arena: self.arena
+      ),
+      unexpectedBeforeRightParen,
+      rightParen: rightParen,
+      trailingClosure: trailingClosure,
+      additionalTrailingClosures: additionalTrailingClosures,
+      arena: self.arena
+    )
+  }
 }

Sources/SwiftParser/Directives.swift

@@ -123,22 +123,6 @@ extension Parser {
 }
 
 extension Parser {
-  /// Parse a #line literal.
-  ///
-  /// Grammar
-  /// =======
-  ///
-  ///     literal-expression → '#line'
-  @_spi(RawSyntax)
-  public mutating func parsePoundLineDirective() -> RawPoundLineExprSyntax {
-    let (unexpectedBeforeToken, token) = self.expect(.poundLineKeyword)
-    return RawPoundLineExprSyntax(
-      unexpectedBeforeToken,
-      poundLine: token,
-      arena: self.arena
-    )
-  }
-
   /// Parse a line control directive.
   ///
   /// Grammar