[SwiftLexicalLookup] Add dollar identifier, better extension handling and more ASTScope related fixes

Sources/SwiftLexicalLookup/LookupResult.swift

@@ -21,8 +21,34 @@ import SwiftSyntax
   /// Indicates where to perform member lookup.
   case lookInMembers(LookInMembersScopeSyntax)
   /// Indicates to lookup generic parameters of extended type.
+  ///
+  /// ### Example
+  /// ```swift
+  /// extension Foo {
+  ///   func bar() {
+  ///     let a = A() // <-- lookup here
+  ///   }
+  /// }
+  /// ```
+  /// For a lookup started at the marked position, `lookInGenericParametersOfExtendedType`
+  /// will be included as one of the results prompting the client
+  /// to lookup the generic parameters of of the extended `Foo` type.
   case lookInGenericParametersOfExtendedType(ExtensionDeclSyntax)
   /// Indicates this closure expression could introduce dollar identifiers.
+  ///
+  /// ### Example
+  /// ```swift
+  /// func foo() {
+  ///   let a = {
+  ///     $0 // <-- lookup here
+  ///   }
+  /// }
+  /// ```
+  /// When looking up for any identifier at the indicated position,
+  /// the result will include `mightIntroduceDollarIdentifiers`
+  /// result kind. If it's performed for a dollar identifier, `LookupName.dollarIdentifier`
+  /// with the appropriate identifier will be used in the
+  /// result associated with the closure expression inside `a`.
   case mightIntroduceDollarIdentifiers(ClosureExprSyntax)
 
   /// Associated scope.

Sources/SwiftLexicalLookup/Scopes/ScopeImplementations.swift

@@ -424,14 +424,14 @@ import SwiftSyntax
       if inRightTypeOrSameTypeRequirement(lookUpPosition) {
         return [.lookInGenericParametersOfExtendedType(self)] + [.lookInMembers(self)]
           + defaultLookupImplementation(identifier, at: lookUpPosition, with: config)
-      } else {
-        return [.lookInGenericParametersOfExtendedType(self)]
-          + defaultLookupImplementation(identifier, at: lookUpPosition, with: config)
       }
-    } else {
+
       return [.lookInGenericParametersOfExtendedType(self)]
-        + lookupInParent(identifier, at: lookUpPosition, with: config)
+        + defaultLookupImplementation(identifier, at: lookUpPosition, with: config)
     }
+
+    return [.lookInGenericParametersOfExtendedType(self)]
+      + lookupInParent(identifier, at: lookUpPosition, with: config)
   }
 
   /// Returns `true` if `checkedPosition` is a right type of a

Tests/SwiftLexicalLookupTest/ExpectedName.swift

@@ -81,10 +81,10 @@ enum NameExpectation: ExpectedName {
     case (.declaration, .declaration): break
     case (.implicit(let implicitName), .implicit(let implicitNameExpectation)):
       implicitNameExpectation.assertExpectation(marker: marker, for: implicitName)
-    case (.dollarIdentifier(_, let acutalStr), .dollarIdentifier(_, let expectedStr)):
+    case (.dollarIdentifier(_, let actualStr), .dollarIdentifier(_, let expectedStr)):
       XCTAssert(
-        acutalStr == expectedStr,
-        "For marker \(marker), actual identifier \(acutalStr) doesn't match expected \(expectedStr)"
+        actualStr == expectedStr,
+        "For marker \(marker), actual identifier \(actualStr) doesn't match expected \(expectedStr)"
       )
     default:
       XCTFail("For marker \(marker), actual name kind \(name) doesn't match expected \(self)")