From b4396f9fe1bcdafee204bd64902bb25749178fe7 Mon Sep 17 00:00:00 2001
From: TiagoMaiaL <tiago.maia.lopes@gmail.com>
Date: Fri, 19 May 2023 00:24:16 -0300
Subject: [PATCH] Improve FixIt for function param with missing type

If the `node.secondName` starts with a capital letter, we now assume the user
wanted it to be the type of the parameter.

This commit makes the following changes to the FixIt of `name1 Name2`:
- from `name1 Name2: TypeText`
- to `name1: Name2`
---
 Sources/SwiftParser/Parameters.swift          | 24 +++++++++++++++++--
 .../translated/InvalidTests.swift             |  6 ++---
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/Sources/SwiftParser/Parameters.swift b/Sources/SwiftParser/Parameters.swift
index 83867b21b9a..f689060d75b 100644
--- a/Sources/SwiftParser/Parameters.swift
+++ b/Sources/SwiftParser/Parameters.swift
@@ -92,10 +92,30 @@ extension Parser {
     let modifiers = parseParameterModifiers(isClosure: false)
     let misplacedSpecifiers = parseMisplacedSpecifiers()
 
-    let names = self.parseParameterNames()
+    var names = self.parseParameterNames()
     let (unexpectedBeforeColon, colon) = self.expect(.colon)
 
-    let type = self.parseType(misplacedSpecifiers: misplacedSpecifiers)
+    let type: RawTypeSyntax
+
+    if colon.presence == .missing, let secondName = names.secondName, secondName.tokenText.isStartingWithUppercase {
+      // Synthesize the secondName parameter as a type node.
+      type = RawTypeSyntax(
+        RawSimpleTypeIdentifierSyntax(
+          name: secondName,
+          genericArgumentClause: nil,
+          arena: self.arena
+        )
+      )
+      names = ParameterNames(
+        unexpectedBeforeFirstName: names.unexpectedBeforeFirstName,
+        firstName: names.firstName,
+        unexpectedBeforeSecondName: nil,
+        secondName: nil
+      )
+    } else {
+      // Parse the type node as we would normally do.
+      type = self.parseType(misplacedSpecifiers: misplacedSpecifiers)
+    }
 
     let ellipsis = self.consumeIfContextualPunctuator("...", remapping: .ellipsis)
 
diff --git a/Tests/SwiftParserTest/translated/InvalidTests.swift b/Tests/SwiftParserTest/translated/InvalidTests.swift
index b411b4f91a6..e94655871e4 100644
--- a/Tests/SwiftParserTest/translated/InvalidTests.swift
+++ b/Tests/SwiftParserTest/translated/InvalidTests.swift
@@ -312,19 +312,19 @@ final class InvalidTests: XCTestCase {
       do {
         class Starfish {}
         struct Salmon {}
-        func f(s Starfish1️⃣,
+        func f(s 1️⃣Starfish,
                   _ ss: Salmon) -> [Int] {}
         func g() { f(Starfish(), Salmon()) }
       }
       """,
       diagnostics: [
-        DiagnosticSpec(message: "expected ':' and type in parameter", fixIts: ["insert ':' and type"])
+        DiagnosticSpec(message: "expected ':' in parameter", fixIts: ["insert ':'"])
       ],
       fixedSource: """
         do {
           class Starfish {}
           struct Salmon {}
-          func f(s Starfish: <#type#>,
+          func f(s: Starfish,
                     _ ss: Salmon) -> [Int] {}
           func g() { f(Starfish(), Salmon()) }
         }