Add diagnostic for empty switch cases

Author: kimdv

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -1034,6 +1034,10 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
       addDiagnostic(node.expression, .missingExpressionInSwitchStatement, handledNodes: [node.expression.id])
     }
 
+      if node.cases.isEmpty && !node.leftBrace.isMissingAllTokens && !node.rightBrace.isMissingAllTokens {
+          addDiagnostic(node.cases, .switchExprBodyEmpty, handledNodes: [node.cases.id])
+      }
+
     return .visitChildren
   }
 

Sources/SwiftParserDiagnostics/ParserDiagnosticMessages.swift

@@ -191,6 +191,9 @@ extension DiagnosticMessage where Self == StaticParserError {
   public static var subscriptsCannotHaveNames: Self {
     .init("subscripts cannot have a name")
   }
+    public static var switchExprBodyEmpty: Self {
+        .init("'switch' statement body must have at least one 'case' or 'default' block")
+    }
   public static var tooManyClosingRawStringDelimiters: Self {
     .init("too many '#' characters in closing delimiter")
   }

Tests/SwiftParserTest/translated/RecoveryTests.swift

@@ -621,12 +621,12 @@ final class RecoveryTests: XCTestCase {
   func testRecovery46() {
     AssertParse(
       """
-      switch 1️⃣{
+      switch 1️⃣{2️⃣
       }
       """,
       diagnostics: [
-        DiagnosticSpec(message: "expected expression in 'switch' statement")
-        // TODO: Old parser expected error on line 1: 'switch' statement body must have at least one 'case' or 'default' block
+        DiagnosticSpec(locationMarker: "1️⃣", message: "expected expression in 'switch' statement"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "'switch' statement body must have at least one 'case' or 'default' block")
       ]
     )
   }
@@ -635,12 +635,12 @@ final class RecoveryTests: XCTestCase {
     AssertParse(
       """
       switch 1️⃣
-      {
+      {2️⃣
       }
       """,
       diagnostics: [
-        DiagnosticSpec(message: "expected expression in 'switch' statement")
-        // TODO: Old parser expected error on line 1: 'switch' statement body must have at least one 'case' or 'default' block
+        DiagnosticSpec(locationMarker: "1️⃣", message: "expected expression in 'switch' statement"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "'switch' statement body must have at least one 'case' or 'default' block")
       ]
     )
   }
@@ -669,8 +669,6 @@ final class RecoveryTests: XCTestCase {
       diagnostics: [
         DiagnosticSpec(locationMarker: "1️⃣", message: "expected expression in 'switch' statement"),
         // TODO: Old parser expected error on line 2: 'is' keyword required to pattern match against type name, Fix-It replacements: 10 - 10 = 'is '
-        DiagnosticSpec(locationMarker: "2️⃣", message: "'case' can only appear inside a 'switch' statement or 'enum' declaration"),
-        DiagnosticSpec(locationMarker: "3️⃣", message: "'case' can only appear inside a 'switch' statement or 'enum' declaration"),
       ]
     )
   }