Parse SwitchExprSyntax

Update the parser to support parsing SwitchExprSyntax.
For now, this only updates the existing statement
parsing, and does not attempt to parse in
expression position.

Author: hamishknight

Sources/SwiftParser/Expressions.swift

@@ -2146,18 +2146,20 @@ extension Parser {
   }
 }
 
-// MARK: Switch Statements
+// MARK: Switch Statements/Expressions
 
 extension Parser {
-  /// Parse a switch statement.
+  /// Parse a switch statement/expression.
   ///
   /// Grammar
   /// =======
   ///
-  ///     switch-statement → 'switch' expression '{' switch-cases? '}'
+  ///     switch-expression → 'switch' expression '{' switch-cases? '}'
   ///     switch-cases → switch-case switch-cases?
   @_spi(RawSyntax)
-  public mutating func parseSwitchStatement(switchHandle: RecoveryConsumptionHandle) -> RawSwitchStmtSyntax {
+  public mutating func parseSwitchExpression(
+    switchHandle: RecoveryConsumptionHandle
+  ) -> RawSwitchExprSyntax {
     let (unexpectedBeforeSwitchKeyword, switchKeyword) = self.eat(switchHandle)
 
     let subject = self.parseExpression(.basic)
@@ -2166,7 +2168,7 @@ extension Parser {
     let cases = self.parseSwitchCases(allowStandaloneStmtRecovery: !lbrace.isMissing)
 
     let (unexpectedBeforeRBrace, rbrace) = self.expectRightBrace(leftBrace: lbrace, introducer: switchKeyword)
-    return RawSwitchStmtSyntax(
+    return RawSwitchExprSyntax(
       unexpectedBeforeSwitchKeyword,
       switchKeyword: switchKeyword,
       expression: subject,

Sources/SwiftParser/Statements.swift

@@ -111,7 +111,12 @@ extension Parser {
     case (.guardKeyword, let handle)?:
       return label(self.parseGuardStatement(guardHandle: handle), with: optLabel)
     case (.switchKeyword, let handle)?:
-      return label(self.parseSwitchStatement(switchHandle: handle), with: optLabel)
+      let switchExpr = self.parseSwitchExpression(switchHandle: handle)
+      let switchStmt = RawExpressionStmtSyntax(
+        expression: RawExprSyntax(switchExpr),
+        arena: self.arena
+      )
+      return label(switchStmt, with: optLabel)
     case (.breakKeyword, let handle)?:
       return label(self.parseBreakStatement(breakHandle: handle), with: optLabel)
     case (.continueKeyword, let handle)?:

Sources/SwiftSyntaxBuilder/SyntaxNodeWithBody.swift

@@ -153,17 +153,17 @@ extension SwitchCaseSyntax {
   }
 }
 
-// MARK: - SwitchStmtSyntax
-// SwitchStmtSyntax is a special scenario as it don't have body or members
+// MARK: - SwitchExprSyntax
+// SwitchExprSyntax is a special scenario as it don't have body or members
 // So we cannot conform to `HasTrailingCodeBlock` or `HasTrailingMemberDeclBlock`
 
-public extension SwitchStmtSyntax {
+public extension SwitchExprSyntax {
   init(_ header: PartialSyntaxNodeString, @SwitchCaseListBuilder casesBuilder: () throws -> SwitchCaseListSyntax = { SwitchCaseListSyntax([]) }) throws {
-    let stmt = StmtSyntax("\(header) {}")
-    guard let castedStmt = stmt.as(Self.self) else {
-      throw SyntaxStringInterpolationError.producedInvalidNodeType(expectedType: Self.self, actualNode: stmt)
+    let expr = ExprSyntax("\(header) {}")
+    guard let switchExpr = expr.as(Self.self) else {
+      throw SyntaxStringInterpolationError.producedInvalidNodeType(expectedType: Self.self, actualNode: expr)
     }
-    self = castedStmt
+    self = switchExpr
     self.cases = try casesBuilder()
   }
 }

Tests/SwiftSyntaxBuilderTest/SwitchTests.swift

@@ -16,7 +16,7 @@ import SwiftSyntaxBuilder
 
 final class SwitchTests: XCTestCase {
   func testSwitch() {
-    let syntax = SwitchStmtSyntax(expression: ExprSyntax("count")) {
+    let syntax = SwitchExprSyntax(expression: ExprSyntax("count")) {
       for num in 1..<3 {
         SwitchCaseSyntax("case \(literal: num):") {
           ExprSyntax("print(count)")
@@ -43,7 +43,7 @@ final class SwitchTests: XCTestCase {
   }
 
   func testSwitchStmtSyntaxWithStringParsing() throws {
-    let syntax = try SwitchStmtSyntax("switch count") {
+    let syntax = try SwitchExprSyntax("switch count") {
       for num in 1..<3 {
         SwitchCaseSyntax("case \(literal: num):") {
           ExprSyntax("print(count)")