Resolve enum constants when emitting types (#1235)

* resolve enum constants

* reuse ClassName

* yikes, fix typo

* better comments

* Update kotlinpoet/src/main/java/com/squareup/kotlinpoet/CodeWriter.kt

Co-authored-by: Egor Andreevich <github@egorand.dev>

Co-authored-by: Egor Andreevich <github@egorand.dev>

kotlinpoet/src/main/java/com/squareup/kotlinpoet/CodeWriter.kt

@@ -518,7 +518,7 @@ internal class CodeWriter constructor(
   }
 
   /**
-   * Returns the class referenced by `simpleName`, using the current nesting context and
+   * Returns the class or enum value referenced by `simpleName`, using the current nesting context and
    * imports.
    */
   // TODO(jwilson): also honor superclass members when resolving names.
@@ -531,9 +531,17 @@ internal class CodeWriter constructor(
       }
     }
 
-    // Match the top-level class.
-    if (typeSpecStack.size > 0 && typeSpecStack[0].name == simpleName) {
-      return ClassName(packageName, simpleName)
+    if (typeSpecStack.size > 0) {
+      val typeSpec = typeSpecStack[0]
+      if (typeSpec.name == simpleName) {
+        // Match the top-level class.
+        return ClassName(packageName, simpleName)
+      }
+      if (typeSpec.isEnum && typeSpec.enumConstants.keys.contains(simpleName)) {
+        // Match a top level enum value.
+        // Enum values are not proper classes but can still be modeled using ClassName.
+        return ClassName(packageName, typeSpec.name!!).nestedClass(simpleName)
+      }
     }
 
     // Match an imported type.

kotlinpoet/src/test/java/com/squareup/kotlinpoet/TypeSpecTest.kt

@@ -5056,6 +5056,36 @@ class TypeSpecTest {
     )
   }
 
+  // https://github.com/square/kotlinpoet/issues/1234
+  @Test fun `enum constants are resolved`() {
+    val file = FileSpec.builder("com.example", "test")
+      .addType(
+        TypeSpec.enumBuilder("Foo")
+          .addProperty(
+            PropertySpec.builder("rawValue", String::class)
+              .initializer("%S", "")
+              .build()
+          )
+          .addEnumConstant("String")
+          .build()
+      )
+      .build()
+
+    assertThat(file.toString()).isEqualTo(
+      """
+    package com.example
+
+    public enum class Foo {
+      String,
+      ;
+
+      public val rawValue: kotlin.String = ""
+    }
+
+      """.trimIndent()
+    )
+  }
+
   companion object {
     private const val donutsPackage = "com.squareup.donuts"
   }