Add diagnostic for missing conditions for while statement

Author: kimdv

Sources/SwiftParser/Statements.swift

@@ -539,7 +539,22 @@ extension Parser {
   @_spi(RawSyntax)
   public mutating func parseWhileStatement(whileHandle: RecoveryConsumptionHandle) -> RawWhileStmtSyntax {
     let (unexpectedBeforeWhileKeyword, whileKeyword) = self.eat(whileHandle)
-    let conditions = self.parseConditionList()
+    let conditions: RawConditionElementListSyntax
+
+    if self.at(.leftBrace) {
+      conditions = RawConditionElementListSyntax(
+        elements: [
+          RawConditionElementSyntax(
+            condition: .expression(RawExprSyntax(RawMissingExprSyntax(arena: self.arena))),
+            trailingComma: nil,
+            arena: self.arena
+          )
+        ],
+        arena: self.arena
+      )
+    } else {
+      conditions = self.parseConditionList()
+    }
     let body = self.parseCodeBlock(introducer: whileKeyword)
     return RawWhileStmtSyntax(
       unexpectedBeforeWhileKeyword,

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -1220,6 +1220,18 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     return .visitChildren
   }
 
+  public override func visit(_ node: WhileStmtSyntax) -> SyntaxVisitorContinueKind {
+    if shouldSkip(node) {
+      return .skipChildren
+    }
+
+    if node.conditions.count == 1, node.conditions.first?.as(ConditionElementSyntax.self)?.condition.is(MissingExprSyntax.self) == true, !node.body.leftBrace.isMissingAllTokens {
+      addDiagnostic(node.conditions, MissingConditionInStatement(firstToken: node.whileKeyword), handledNodes: [node.conditions.id])
+    }
+
+    return .visitChildren
+  }
+
   //==========================================================================//
   // IMPORTANT: If you are tempted to add a `visit` method here, please       //
   // insert it in alphabetical order above                                    //

Tests/SwiftParserTest/translated/RecoveryTests.swift

@@ -268,26 +268,24 @@ final class RecoveryTests: XCTestCase {
   func testRecovery21() {
     assertParse(
       """
-      while {
-        }1️⃣
+      while 1️⃣{
+        }
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: missing condition in 'while' statement
-        DiagnosticSpec(message: "expected code block in 'while' statement")
+        DiagnosticSpec(message: "missing condition in 'while' statement")
       ]
     )
   }
 
   func testRecovery22() {
     assertParse(
       """
-      while
+      while 1️⃣
         {
-        }1️⃣
+        }
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: missing condition in 'while' statement
-        DiagnosticSpec(message: "expected code block in 'while' statement")
+        DiagnosticSpec(message: "missing condition in 'while' statement")
       ]
     )
   }
@@ -297,11 +295,11 @@ final class RecoveryTests: XCTestCase {
       """
       // It is debatable if we should do recovery here and parse { true } as the
       // body, but the error message should be sensible.
-      while { true } {
+      while 1️⃣{ true } {
       }
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 3: missing condition in 'while' statement
+        DiagnosticSpec(message: "missing condition in 'while' statement")
         // TODO: Old parser expected error on line 3: consecutive statements on a line must be separated by ';', Fix-It replacements: 17 - 17 = ';'
         // TODO: Old parser expected error on line 3: closure expression is unused
         // TODO: Old parser expected note on line 3: did you mean to use a 'do' statement?, Fix-It replacements: 18 - 18 = 'do '
@@ -313,11 +311,11 @@ final class RecoveryTests: XCTestCase {
   func testRecovery24() {
     assertParse(
       """
-      while { true }() { //  expected-error 2 {{consecutive statements on a line must be separated by ';'}} expected-error {{closure expression is unused}} expected-note {{did you mean to use a 'do' statement?}} {{20-20=do }} expected-warning {{boolean literal is unused}}
+      while 1️⃣{ true }() {
       }
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: missing condition in 'while' statement
+        DiagnosticSpec(message: "missing condition in 'while' statement")
       ]
     )
   }
@@ -326,13 +324,12 @@ final class RecoveryTests: XCTestCase {
     assertParse(
       """
       // <rdar://problem/18940198>
-      while { { } }1️⃣
+      while 1️⃣{ { } }
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 2: missing condition in 'while' statement
+        DiagnosticSpec(message: "missing condition in 'while' statement")
         // TODO: Old parser expected error on line 2: closure expression is unused
         // TODO: Old parser expected note on line 2: did you mean to use a 'do' statement?, Fix-It replacements: 11 - 11 = 'do '
-        DiagnosticSpec(message: "expected code block in 'while' statement")
       ]
     )
   }