Parser support for do..catch blocks with typed throws

Author: DougGregor

Sources/SwiftParser/Specifiers.swift

@@ -583,7 +583,7 @@ extension TokenConsumer {
 
 extension Parser {
   /// Parse a throws clause after we've already parsed the 'throws' keyword to introduce it.
-  private mutating func parseThrowsClause(after throwsKeyword: RawTokenSyntax) -> RawThrowsClauseSyntax {
+  mutating func parseThrowsClause(after throwsKeyword: RawTokenSyntax) -> RawThrowsClauseSyntax {
     guard self.at(.leftParen) && experimentalFeatures.contains(.typedThrows) else {
       return RawThrowsClauseSyntax(
         throwsSpecifier: throwsKeyword,

Sources/SwiftParser/Statements.swift

@@ -389,6 +389,15 @@ extension Parser {
   /// Parse a do statement.
   mutating func parseDoStatement(doHandle: RecoveryConsumptionHandle) -> RawDoStmtSyntax {
     let (unexpectedBeforeDoKeyword, doKeyword) = self.eat(doHandle)
+
+    // Parse the optional throws clause.
+    let throwsClause: RawThrowsClauseSyntax?
+    if let throwsSpecifier = self.consume(if: .keyword(.throws)) {
+      throwsClause = parseThrowsClause(after: throwsSpecifier)
+    } else {
+      throwsClause = nil
+    }
+
     let body = self.parseCodeBlock(introducer: doKeyword)
 
     // If the next token is 'catch', this is a 'do'/'catch' statement.
@@ -402,6 +411,7 @@ extension Parser {
     return RawDoStmtSyntax(
       unexpectedBeforeDoKeyword,
       doKeyword: doKeyword,
+      throwsClause: throwsClause,
       body: body,
       catchClauses: RawCatchClauseListSyntax(elements: elements, arena: self.arena),
       arena: self.arena

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -282,13 +282,13 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
       }
     }
 
-    if let throwsSpecifier = node.throwsSpecifier {
+    if let throwsClause = node.throwsClause {
       exchangeTokens(
         unexpected: node.unexpectedAfterThrowsClause,
         unexpectedTokenCondition: { AsyncEffectSpecifier(token: $0) != nil },
         correctTokens: [node.asyncSpecifier],
-        message: { AsyncMustPrecedeThrows(asyncKeywords: $0, throwsKeyword: throwsSpecifier) },
-        moveFixIt: { MoveTokensInFrontOfFixIt(movedTokens: $0, inFrontOf: throwsSpecifier.tokenKind) },
+        message: { AsyncMustPrecedeThrows(asyncKeywords: $0, throwsKeyword: throwsClause.throwsSpecifier) },
+        moveFixIt: { MoveTokensInFrontOfFixIt(movedTokens: $0, inFrontOf: throwsClause.throwsSpecifier.tokenKind) },
         removeRedundantFixIt: { RemoveRedundantFixIt(removeTokens: $0) }
       )
     }

Tests/SwiftParserTest/StatementTests.swift

@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-@_spi(RawSyntax) import SwiftParser
+@_spi(RawSyntax) @_spi(ExperimentalLanguageFeatures) import SwiftParser
 @_spi(RawSyntax) import SwiftSyntax
 import XCTest
 
@@ -895,4 +895,33 @@ final class StatementTests: ParserTestCase {
         """
     )
   }
+
+  func testTypedThrows() {
+    assertParse(
+      """
+      do throws(any Error) {
+        throw myError
+      }
+      """,
+      experimentalFeatures: [.typedThrows]
+    )
+
+    assertParse(
+      """
+      do throws(MyError) {
+        throw myError
+      }
+      """,
+      experimentalFeatures: [.typedThrows]
+    )
+
+    assertParse(
+      """
+      do throws {
+        throw myError
+      }
+      """,
+      experimentalFeatures: [.typedThrows]
+    )
+  }
 }