Builder based initializer for DictionaryExpr

Allow to use `ArrayType` and `DictionaryType`
  as `PatternBinding.typeAnnotation` argument

Author: evnik

Sources/SwiftSyntaxBuilder/DictionaryExprConvenienceInitializers.swift

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+
+extension DictionaryExpr {
+  /// A convenience initializer that allows passing in members using a result builder
+  /// instead of having to wrap them in a `DictionaryElementList`.
+  public init(
+    leftSquare: TokenSyntax = .`leftSquareBracket`,
+    rightSquare: TokenSyntax = .`rightSquareBracket`,
+    @DictionaryElementListBuilder contentBuilder: () -> ExpressibleAsDictionaryElementList = { DictionaryElementList([]) }
+  ) {
+    let elementList = contentBuilder().createDictionaryElementList()
+    self.init(
+      leftSquare: leftSquare,
+      content: elementList.elements.isEmpty ? SyntaxFactory.makeColonToken() : elementList,
+      rightSquare: rightSquare
+    )
+  }
+}

Sources/SwiftSyntaxBuilder/gyb_generated/ExpressibleAsProtocols.swift

@@ -2109,21 +2109,29 @@ public extension ExpressibleAsClassRestrictionType {
   }
 }
 
-public protocol ExpressibleAsArrayType: ExpressibleAsTypeBuildable {
+public protocol ExpressibleAsArrayType: ExpressibleAsTypeAnnotation, ExpressibleAsTypeBuildable {
   func createArrayType() -> ArrayType
 }
 
 public extension ExpressibleAsArrayType {
+  /// Conformance to `ExpressibleAsTypeAnnotation`.
+  func createTypeAnnotation() -> TypeAnnotation {
+    return TypeAnnotation(type: self)
+  }
   func createTypeBuildable() -> TypeBuildable {
     return self.createArrayType()
   }
 }
 
-public protocol ExpressibleAsDictionaryType: ExpressibleAsTypeBuildable {
+public protocol ExpressibleAsDictionaryType: ExpressibleAsTypeAnnotation, ExpressibleAsTypeBuildable {
   func createDictionaryType() -> DictionaryType
 }
 
 public extension ExpressibleAsDictionaryType {
+  /// Conformance to `ExpressibleAsTypeAnnotation`.
+  func createTypeAnnotation() -> TypeAnnotation {
+    return TypeAnnotation(type: self)
+  }
   func createTypeBuildable() -> TypeBuildable {
     return self.createDictionaryType()
   }

Sources/SwiftSyntaxBuilder/gyb_helpers/ExpressibleAsConformances.py

@@ -2,13 +2,19 @@
     'AccessorList': [
         'AccessorBlock'
     ],
+    'ArrayType': [
+        'TypeAnnotation'
+    ],
     'CodeBlockItemList': [
         'CodeBlock'
     ],
     'DeclBuildable': [
         'CodeBlockItem',
         'MemberDeclListItem'
     ],
+    'DictionaryType': [
+        'TypeAnnotation'
+    ],
     'ExprList': [
         'ConditionElement'
     ],

Tests/SwiftSyntaxBuilderTest/VariableTests.swift

@@ -6,18 +6,19 @@ final class VariableTests: XCTestCase {
   func testVariableDecl() {
     let leadingTrivia = Trivia.garbageText("␣")
 
-    let buildable = VariableDecl(letOrVarKeyword: .let, bindingsBuilder:  {
-        PatternBinding(pattern: "color", typeAnnotation: "UIColor")
+    let buildable = VariableDecl(letOrVarKeyword: .let, bindingsBuilder: {
+      PatternBinding(
+        pattern: "d",
+        typeAnnotation: DictionaryType(keyType: "String", valueType: "Int"),
+        initializer: InitializerClause(value: DictionaryExpr()))
     })
 
     let syntax = buildable.buildSyntax(format: Format(), leadingTrivia: leadingTrivia)
 
     var text = ""
     syntax.write(to: &text)
 
-    XCTAssertEqual(text, """
-    ␣let color: UIColor
-    """)
+    XCTAssertEqual(text, "␣let d: [String: Int] = [:]")
   }
 
   func testVariableDeclWithValue() {