Add diagnostic for equal with missing trailing or leading space

Author: kimdv

Sources/SwiftParser/Lexer/Cursor.swift

@@ -1967,7 +1967,23 @@ extension Lexer.Cursor {
     if self.input.baseAddress! - tokStart.input.baseAddress! == 1 {
       switch tokStart.peek() {
       case UInt8(ascii: "="):
-        return Lexer.Result(.equal)
+        if leftBound != rightBound {
+          var errorPos = tokStart
+
+          if rightBound {
+            _ = errorPos.advance()
+          }
+
+          return Lexer.Result(
+            .equal,
+            error: LexingDiagnostic(
+              .equalMustHaveConsistentWhitespaceOnBothSides,
+              position: errorPos
+            )
+          )
+        } else {
+          return Lexer.Result(.equal)
+        }
       case UInt8(ascii: "&"):
         if leftBound == rightBound || leftBound {
           break

Sources/SwiftParserDiagnostics/LexerDiagnosticMessages.swift

@@ -39,6 +39,7 @@ public extension TokenError {
 /// Please order the cases in this enum alphabetically by case name.
 public enum StaticTokenError: String, DiagnosticMessage {
   case editorPlaceholder = "editor placeholder in source file"
+  case equalMustHaveConsistentWhitespaceOnBothSides = "'=' must have consistent whitespace on both sides"
   case expectedBinaryExponentInHexFloatLiteral = "hexadecimal floating point literal must end with an exponent"
   case expectedClosingBraceInUnicodeEscape = #"expected '}' in \u{...} escape sequence"#
   case expectedDigitInFloatLiteral = "expected a digit in floating point exponent"
@@ -134,6 +135,7 @@ public extension SwiftSyntax.TokenDiagnostic {
 
     switch self.kind {
     case .editorPlaceholder: return StaticTokenError.editorPlaceholder
+    case .equalMustHaveConsistentWhitespaceOnBothSides: return StaticTokenError.equalMustHaveConsistentWhitespaceOnBothSides
     case .expectedBinaryExponentInHexFloatLiteral: return StaticTokenError.expectedBinaryExponentInHexFloatLiteral
     case .expectedClosingBraceInUnicodeEscape: return StaticTokenError.expectedClosingBraceInUnicodeEscape
     case .expectedDigitInFloatLiteral: return StaticTokenError.expectedDigitInFloatLiteral

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -771,6 +771,23 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     if shouldSkip(node) {
       return .skipChildren
     }
+
+    if node.equal.hasError && node.equal.presence == .present {
+      var leadingTrivia: Trivia = []
+      if node.previousToken(viewMode: .all)?.trailingTrivia.contains(where: { $0.isSpaceOrTab || $0.isNewline }) == false {
+        leadingTrivia = .space
+      }
+
+      addDiagnostic(
+        node.equal,
+        StaticTokenError.equalMustHaveConsistentWhitespaceOnBothSides,
+        fixIts: [
+          FixIt(message: .insertWhitespace, changes: .makePresent(node.equal, leadingTrivia: leadingTrivia, trailingTrivia: .space))
+        ],
+        handledNodes: [node.equal.id]
+      )
+    }
+
     if node.equal.presence == .missing {
       exchangeTokens(
         unexpected: node.unexpectedBeforeEqual,

Sources/SwiftParserDiagnostics/ParserDiagnosticMessages.swift

@@ -498,6 +498,9 @@ extension FixItMessage where Self == StaticParserFixIt {
   public static var insertNewline: Self {
     .init("insert newline")
   }
+  public static var insertWhitespace: Self {
+    .init("insert whitespace")
+  }
   public static var joinIdentifiers: Self {
     .init("join the identifiers together")
   }

Sources/SwiftSyntax/TokenDiagnostic.swift

@@ -23,6 +23,7 @@ public struct TokenDiagnostic: Hashable {
     // Please order these alphabetically
 
     case editorPlaceholder
+    case equalMustHaveConsistentWhitespaceOnBothSides
     case expectedBinaryExponentInHexFloatLiteral
     case expectedClosingBraceInUnicodeEscape
     case expectedDigitInFloatLiteral
@@ -96,6 +97,7 @@ public struct TokenDiagnostic: Hashable {
   public var severity: Severity {
     switch kind {
     case .editorPlaceholder: return .error
+    case .equalMustHaveConsistentWhitespaceOnBothSides: return .error
     case .expectedBinaryExponentInHexFloatLiteral: return .error
     case .expectedClosingBraceInUnicodeEscape: return .error
     case .expectedDigitInFloatLiteral: return .error

Tests/SwiftParserTest/translated/RecoveryTests.swift

@@ -1962,14 +1962,21 @@ final class RecoveryTests: XCTestCase {
       """
       // <rdar://problem/22387625> QoI: Common errors: 'let x= 5' and 'let x =5' could use Fix-its
       func r22387625() {
-        let _= 5
-        let _ =5
+        let _1️⃣= 4
+        let _ =2️⃣5
       }
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 3: '=' must have consistent whitespace on both sides, Fix-It replacements: 8 - 8 = ' '
-        // TODO: Old parser expected error on line 4: '=' must have consistent whitespace on both sides, Fix-It replacements: 10 - 10 = ' '
-      ]
+        DiagnosticSpec(locationMarker: "1️⃣", message: "'=' must have consistent whitespace on both sides"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "'=' must have consistent whitespace on both sides"),
+      ],
+      fixedSource: """
+        // <rdar://problem/22387625> QoI: Common errors: 'let x= 5' and 'let x =5' could use Fix-its
+        func r22387625() {
+          let _ = 4
+          let _ = 5
+        }
+        """
     )
   }
 
@@ -1978,14 +1985,22 @@ final class RecoveryTests: XCTestCase {
       """
       // https://github.com/apple/swift/issues/45723
       do {
-        let _: Int= 5
-        let _: Array<Int>= []
+        let _: Int1️⃣= 5
+        let _: Array<Int>2️⃣= []
       }
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 3: '=' must have consistent whitespace on both sides, Fix-It replacements: 13 - 13 = ' '
-        // TODO: Old parser expected error on line 4: '=' must have consistent whitespace on both sides, Fix-It replacements: 20 - 20 = ' '
-      ]
+        DiagnosticSpec(locationMarker: "1️⃣", message: "'=' must have consistent whitespace on both sides"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "'=' must have consistent whitespace on both sides"),
+      ],
+      applyFixIts: ["insert whitespace", "insert whitespace"],
+      fixedSource: """
+        // https://github.com/apple/swift/issues/45723
+        do {
+          let _: Int = 5
+          let _: Array<Int> = []
+        }
+        """
     )
   }