Fix wrong diagnostic parse typed pattern

Author: kimdv

Sources/SwiftParser/Patterns.swift

@@ -175,10 +175,12 @@ extension Parser {
       && !self.currentToken.isAtStartOfLine
       && lookahead.canParseType()
     {
-      // Recovery if the user forgot to add ':'
-      let result = self.parseResultType()
+      let (unexpectedBeforeColon, colon) = self.expect(.colon)
+      let result = self.parseType()
+
       type = RawTypeAnnotationSyntax(
-        colon: self.missingToken(.colon),
+        unexpectedBeforeColon,
+        colon: colon,
         type: result,
         arena: self.arena
       )

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -1414,6 +1414,36 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     return .visitChildren
   }
 
+  public override func visit(_ node: PatternBindingSyntax) -> SyntaxVisitorContinueKind {
+    if shouldSkip(node) {
+      return .skipChildren
+    }
+
+    if let identifierPattern = node.pattern.as(IdentifierPatternSyntax.self),
+      let unexpectedBeforeColon = node.typeAnnotation?.unexpectedBeforeColon,
+      let token = unexpectedBeforeColon.onlyToken(where: { $0.tokenKind.isIdentifier })
+    {
+      addDiagnostic(
+        unexpectedBeforeColon,
+        SpaceSeparatedIdentifiersError(
+          firstToken: identifierPattern.identifier,
+          additionalTokens: [token]
+        ),
+        fixIts: [
+          FixIt(
+            message: .joinIdentifiers,
+            changes: [
+              FixIt.MultiNodeChange(.replaceTrailingTrivia(token: identifierPattern.identifier, newTrivia: []))
+            ]
+          )
+        ],
+        handledNodes: [unexpectedBeforeColon.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

@@ -813,9 +813,9 @@ final class RecoveryTests: XCTestCase {
     assertParse(
       #"""
       struct SS 1️⃣SS : Multi {
-        private var a 2️⃣b 3️⃣: Int = ""
+        private var a 2️⃣b : Int = ""
         func f() {
-          var c 4️⃣d = 5
+          var c 3️⃣d = 5
           let _ = 0
         }
       }
@@ -828,16 +828,24 @@ final class RecoveryTests: XCTestCase {
         ),
         DiagnosticSpec(
           locationMarker: "2️⃣",
-          message: "expected ':' in type annotation",
-          fixIts: ["insert ':'"]
+          message: "found an unexpected second identifier in pattern; is there an accidental break?",
+          fixIts: ["join the identifiers together"]
         ),
-        DiagnosticSpec(locationMarker: "3️⃣", message: #"unexpected code ': Int = ""' before function"#),
         DiagnosticSpec(
-          locationMarker: "4️⃣",
+          locationMarker: "3️⃣",
           message: "expected ':' in type annotation",
           fixIts: ["insert ':'"]
         ),
-      ]
+      ],
+      fixedSource: #"""
+        struct SSSS : Multi {
+          private var ab : Int = ""
+          func f() {
+            var c: d = 5
+            let _ = 0
+          }
+        }
+        """#
     )
   }
 
@@ -869,6 +877,24 @@ final class RecoveryTests: XCTestCase {
     )
   }
 
+  func testRecovery64c() {
+    assertParse(
+      """
+      private var a 1️⃣b : Int = ""
+      """,
+      diagnostics: [
+        DiagnosticSpec(
+          locationMarker: "1️⃣",
+          message: "found an unexpected second identifier in pattern; is there an accidental break?",
+          fixIts: ["join the identifiers together"]
+        )
+      ],
+      fixedSource: """
+        private var ab : Int = ""
+        """
+    )
+  }
+
   func testRecovery65() {
     assertParse(
       """