Update parseType to support Swift 6.4 :: module selector syntax (#2399)

Co-authored-by: calda <1811727+calda@users.noreply.github.com>

Sources/ParsingHelpers.swift

@@ -1490,6 +1490,17 @@ extension Formatter {
             return TypeName(range: startOfTypeIndex ... followingType.range.upperBound, formatter: self)
         }
 
+        // `::` can also continue a type (e.g. `Module::Type`), but unlike `.` and `&`,
+        // there must be no newline between `::` and the following identifier.
+        if let nextTokenIndex = index(of: .nonSpaceOrCommentOrLinebreak, after: baseType.range.upperBound),
+           tokens[nextTokenIndex] == .operator("::", .infix),
+           let afterDoubleColonIndex = index(of: .nonSpaceOrComment, after: nextTokenIndex),
+           !tokens[afterDoubleColonIndex].isLinebreak,
+           let followingType = parseType(at: afterDoubleColonIndex, excludeLowercaseIdentifiers: excludeLowercaseIdentifiers)
+        {
+            return TypeName(range: startOfTypeIndex ... followingType.range.upperBound, formatter: self)
+        }
+
         return baseType
     }
 

Tests/ParsingHelpersTests.swift

@@ -2397,6 +2397,36 @@ final class ParsingHelpersTests: XCTestCase {
         XCTAssertEqual(formatter.parseType(at: 2)?.string, "Foo.Bar.Baaz.Quux.InnerType1.InnerType2")
     }
 
+    func testParseModuleQualifiedType() {
+        let formatter = Formatter(tokenize("""
+        let foo: Module::Type
+        """))
+        XCTAssertEqual(formatter.parseType(at: 5)?.string, "Module::Type")
+    }
+
+    func testParseNestedModuleQualifiedType() {
+        let formatter = Formatter(tokenize("""
+        let foo: Module::Type.Module::Subtype
+        """))
+        XCTAssertEqual(formatter.parseType(at: 5)?.string, "Module::Type.Module::Subtype")
+    }
+
+    func testParseModuleQualifiedTypeWithNewlineBeforeDoubleColon() {
+        let formatter = Formatter(tokenize("""
+        let foo: NationalAeronauticsAndSpaceAdministration
+            ::RocketEngine
+        """))
+        XCTAssertEqual(formatter.parseType(at: 5)?.string, "NationalAeronauticsAndSpaceAdministration::RocketEngine")
+    }
+
+    func testDoesntParseModuleQualifiedTypeWithNewlineAfterDoubleColon() {
+        let formatter = Formatter(tokenize("""
+        let foo: NationalAeronauticsAndSpaceAdministration::
+            RocketEngine
+        """))
+        XCTAssertEqual(formatter.parseType(at: 5)?.string, "NationalAeronauticsAndSpaceAdministration")
+    }
+
     func testParseTuples() {
         let input = """
         let tuple: (foo: Foo, bar: Bar)