Add parsing of generic arguments in macro expansions

Author: DougGregor

Sources/SwiftParser/Declarations.swift

@@ -2018,6 +2018,14 @@ extension Parser {
     let poundKeyword = self.consumeAnyToken()
     let (unexpectedBeforeMacro, macro) = self.expectIdentifier()
 
+    // Parse the optional generic argument list.
+    let generics: RawGenericArgumentClauseSyntax?
+    if self.lookahead().canParseAsGenericArgumentList() {
+      generics = self.parseGenericArguments()
+    } else {
+      generics = nil
+    }
+
     // Parse the optional parenthesized argument list.
     let leftParen = self.consume(if: .leftParen, where: { !$0.isAtStartOfLine })
     let args: [RawTupleExprElementSyntax]
@@ -2048,6 +2056,7 @@ extension Parser {
       poundToken: poundKeyword,
       unexpectedBeforeMacro,
       macro: macro,
+      genericArguments: generics,
       leftParen: leftParen,
       argumentList: RawTupleExprElementListSyntax(
         elements: args, arena: self.arena

Sources/SwiftParser/Expressions.swift

@@ -1163,6 +1163,14 @@ extension Parser {
     let poundKeyword = self.consumeAnyToken()
     let (unexpectedBeforeMacro, macro) = self.expectIdentifier()
 
+    // Parse the optional generic argument list.
+    let generics: RawGenericArgumentClauseSyntax?
+    if self.lookahead().canParseAsGenericArgumentList() {
+      generics = self.parseGenericArguments()
+    } else {
+      generics = nil
+    }
+
     // Parse the optional parenthesized argument list.
     let leftParen = self.consume(if: .leftParen, where: { !$0.isAtStartOfLine })
     let args: [RawTupleExprElementSyntax]
@@ -1191,6 +1199,7 @@ extension Parser {
       poundToken: poundKeyword,
       unexpectedBeforeMacro,
       macro: macro,
+      genericArguments: generics,
       leftParen: leftParen,
       argumentList: RawTupleExprElementListSyntax(
         elements: args, arena: self.arena

Sources/_SwiftSyntaxMacros/Syntax+MacroEvaluation.swift

@@ -49,7 +49,8 @@ extension MacroExpansionDeclSyntax {
     MacroExpansionExprSyntax(
       unexpectedBeforePoundToken, poundToken: poundToken,
       unexpectedBetweenPoundTokenAndMacro, macro: macro,
-      unexpectedBetweenMacroAndLeftParen, leftParen: leftParen,
+      genericArguments: genericArguments,
+      unexpectedBetweenGenericArgumentsAndLeftParen, leftParen: leftParen,
       unexpectedBetweenLeftParenAndArgumentList, argumentList: argumentList,
       unexpectedBetweenArgumentListAndRightParen, rightParen: rightParen,
       unexpectedBetweenRightParenAndTrailingClosure,

Tests/SwiftParserTest/ExpressionTests.swift

@@ -343,6 +343,12 @@ final class ExpressionTests: XCTestCase {
           additionalTrailingClosures: nil)),
         trailingComma: .commaToken())),
     substructureAfterMarker: "1️⃣")
+
+    AssertParse(
+      """
+      #fancyMacro<Arg1, Arg2>(hello: "me")
+      """
+    )
   }
 
   func testInterpolatedStringLiterals() {