Fix CastToNullableType warning on same or parent type (#6677)

detekt · Jan 3, 2024 · 44f22f1 · 44f22f1
1 parent 3e946a4
commit 44f22f1
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Showing 2 changed files with 74 additions and 6 deletions.
diff --git a/...s-errorprone/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/bugs/CastToNullableType.kt b/...s-errorprone/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/bugs/CastToNullableType.kt
@@ -5,9 +5,12 @@ import io.gitlab.arturbosch.detekt.api.Config
 import io.gitlab.arturbosch.detekt.api.Entity
 import io.gitlab.arturbosch.detekt.api.Issue
 import io.gitlab.arturbosch.detekt.api.Rule
+import io.gitlab.arturbosch.detekt.api.internal.RequiresTypeResolution
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.KtBinaryExpressionWithTypeRHS
 import org.jetbrains.kotlin.psi.KtNullableType
+import org.jetbrains.kotlin.resolve.BindingContext
+import org.jetbrains.kotlin.types.typeUtil.supertypes
 
 /**
  * Reports unsafe cast to nullable types.
@@ -25,6 +28,8 @@ import org.jetbrains.kotlin.psi.KtNullableType
  * }
  * </compliant>
  */
+
+@RequiresTypeResolution
 class CastToNullableType(config: Config = Config.empty) : Rule(config) {
     override val issue: Issue = Issue(
         javaClass.simpleName,
@@ -39,6 +44,11 @@ class CastToNullableType(config: Config = Config.empty) : Rule(config) {
         if (operationReference.getReferencedNameElementType() != KtTokens.AS_KEYWORD) return
         if (expression.left.text == KtTokens.NULL_KEYWORD.value) return
         val nullableTypeElement = expression.right?.typeElement as? KtNullableType ?: return
+        val expressionType =
+            bindingContext[BindingContext.EXPRESSION_TYPE_INFO, expression.left]?.type ?: return
+        val castedType = bindingContext[BindingContext.TYPE, expression.right] ?: return
+
+        if (expressionType == castedType || expressionType.supertypes().contains(castedType)) return
 
         val message = "Use the safe cast ('as? ${nullableTypeElement.innerType?.text}')" +
             " instead of 'as ${nullableTypeElement.text}'."

diff --git a/...rorprone/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/bugs/CastToNullableTypeSpec.kt b/...rorprone/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/bugs/CastToNullableTypeSpec.kt
@@ -1,10 +1,13 @@
 package io.gitlab.arturbosch.detekt.rules.bugs
 
+import io.gitlab.arturbosch.detekt.rules.KotlinCoreEnvironmentTest
 import io.gitlab.arturbosch.detekt.test.assertThat
-import io.gitlab.arturbosch.detekt.test.compileAndLint
+import io.gitlab.arturbosch.detekt.test.compileAndLintWithContext
+import org.jetbrains.kotlin.cli.jvm.compiler.KotlinCoreEnvironment
 import org.junit.jupiter.api.Test
 
-class CastToNullableTypeSpec {
+@KotlinCoreEnvironmentTest
+class CastToNullableTypeSpec(private val env: KotlinCoreEnvironment) {
     private val subject = CastToNullableType()
 
     @Test
@@ -14,20 +17,31 @@ class CastToNullableTypeSpec {
                 val x: String? = a as String?
             }
         """.trimIndent()
-        val findings = subject.compileAndLint(code)
+        val findings = subject.compileAndLintWithContext(env, code)
         assertThat(findings).hasSize(1)
         assertThat(findings).hasStartSourceLocation(2, 24)
         assertThat(findings[0]).hasMessage("Use the safe cast ('as? String') instead of 'as String?'.")
     }
 
+    @Test
+    fun `casting to nullable parent types is allowed`() {
+        val code = """
+            fun foo(a: String?) {
+                val x = a as CharSequence?
+            }
+        """.trimIndent()
+        val findings = subject.compileAndLintWithContext(env, code)
+        assertThat(findings).isEmpty()
+    }
+
     @Test
     fun `safe casting`() {
         val code = """
             fun foo(a: Any?) {
                 val x: String? = a as? String
             }
         """.trimIndent()
-        val findings = subject.compileAndLint(code)
+        val findings = subject.compileAndLintWithContext(env, code)
         assertThat(findings).isEmpty()
     }
 
@@ -38,7 +52,7 @@ class CastToNullableTypeSpec {
                 val x = a is String?
             }
         """.trimIndent()
-        val findings = subject.compileAndLint(code)
+        val findings = subject.compileAndLintWithContext(env, code)
         assertThat(findings).isEmpty()
     }
 
@@ -49,7 +63,51 @@ class CastToNullableTypeSpec {
                 val x = null as String?
             }
         """.trimIndent()
-        val findings = subject.compileAndLint(code)
+        val findings = subject.compileAndLintWithContext(env, code)
+        assertThat(findings).isEmpty()
+    }
+
+    // https://github.com/detekt/detekt/issues/6676
+    @Test
+    fun `cast to same type in alias form allowed`() {
+        val code = """
+            typealias Alias = String
+
+            fun test(s: String?) {
+                @Suppress("USELESS_CAST") // Casts is useful to convert String to typealias.
+                val a = s as Alias?
+                print(a)
+            }
+        """.trimIndent()
+        val findings = subject.compileAndLintWithContext(env, code)
         assertThat(findings).isEmpty()
     }
+
+    @Test
+    fun `cast to parent type in alias form allowed`() {
+        val code = """
+            typealias Alias = CharSequence
+
+            fun test(s: String?) {
+                val a = s as Alias?
+                print(a)
+            }
+        """.trimIndent()
+        val findings = subject.compileAndLintWithContext(env, code)
+        assertThat(findings).isEmpty()
+    }
+
+    @Test
+    fun `cast to different type in alias form not allowed`() {
+        val code = """
+            typealias Alias = String
+
+            fun test(s: Any?) {
+                val a = s as Alias?
+                print(a)
+            }
+        """.trimIndent()
+        val findings = subject.compileAndLintWithContext(env, code)
+        assertThat(findings).hasSize(1)
+    }
 }