UseOrEmpty: fix false positive for indexing operator calls with type …

…parameters (#4804) * UseOrEmpty: fix false positive for indexing operator calls with type parameters * Fix test
detekt · May 5, 2022 · da0c924 · da0c924
1 parent 61cfc24
commit da0c924
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diff --git a/detekt-rules-style/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/UseOrEmpty.kt b/detekt-rules-style/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/UseOrEmpty.kt
@@ -8,12 +8,15 @@ import io.gitlab.arturbosch.detekt.api.Issue
 import io.gitlab.arturbosch.detekt.api.Rule
 import io.gitlab.arturbosch.detekt.api.Severity
 import io.gitlab.arturbosch.detekt.api.internal.RequiresTypeResolution
+import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.psi.KtArrayAccessExpression
 import org.jetbrains.kotlin.psi.KtBinaryExpression
 import org.jetbrains.kotlin.psi.KtCallExpression
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.psi.KtStringTemplateExpression
+import org.jetbrains.kotlin.psi2ir.deparenthesize
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.calls.util.getResolvedCall
 import org.jetbrains.kotlin.resolve.calls.util.getType
@@ -61,6 +64,14 @@ class UseOrEmpty(config: Config = Config.empty) : Rule(config) {
 
         val leftType = left.getType(bindingContext) ?: return
         if (!leftType.isNullable()) return
+        if (left.deparenthesize() is KtArrayAccessExpression) {
+            val functionDescriptor = left.getResolvedCall(bindingContext)?.resultingDescriptor as? FunctionDescriptor
+            if (functionDescriptor != null &&
+                functionDescriptor.isOperator &&
+                functionDescriptor.typeParameters.isNotEmpty()
+            ) return
+        }
+
         val rightType = right.getType(bindingContext) ?: return
         if (!leftType.makeNotNullable().isSubtypeOf(rightType)) return
 

diff --git a/detekt-rules-style/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/style/UseOrEmptySpec.kt b/detekt-rules-style/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/style/UseOrEmptySpec.kt
@@ -146,6 +146,20 @@ class UseOrEmptySpec(val env: KotlinCoreEnvironment) {
             val findings = subject.compileAndLintWithContext(env, code)
             assertThat(findings).hasSize(1)
         }
+
+        @Test
+        fun `indexing operator call`() {
+            val code = """
+                class C {
+                    operator fun get(key: String): List<Int>? = null
+                }
+                fun test(c: C) {
+                    c["key"] ?: emptyList()
+                }
+            """
+            val findings = subject.compileAndLintWithContext(env, code)
+            assertThat(findings).hasSize(1)
+        }
     }
 
     @Nested
@@ -178,6 +192,9 @@ class UseOrEmptySpec(val env: KotlinCoreEnvironment) {
                 fun test(x: List<Int>?) {
                     val a = x ?: emptySet()
                 }
+                fun test(c: Any?) {
+                    val x = c ?: emptyList<Int>()
+                }
             """
             val findings = subject.compileAndLintWithContext(env, code)
             assertThat(findings).isEmpty()
@@ -204,5 +221,21 @@ class UseOrEmptySpec(val env: KotlinCoreEnvironment) {
             val findings = subject.compileAndLintWithContext(env, code)
             assertThat(findings).isEmpty()
         }
+
+        @Test
+        fun `indexing operator call with type parameter`() {
+            val code = """
+                class C {
+                    operator fun <T> get(key: String): List<T>? = null
+                }
+                fun test(c: C) {
+                    val x = c["key"] ?: emptyList<Int>()
+                    val y: List<Int> = c["key"] ?: emptyList()
+                    val z = (c["key"]) ?: emptyList<Int>()
+                }
+            """
+            val findings = subject.compileAndLintWithContext(env, code)
+            assertThat(findings).isEmpty()
+        }
     }
 }