[stdlib] Specify AT_MOST_ONCE contract for default-value-like functional parameters KT-54879

libraries/tools/kotlin-stdlib-gen/src/templates/Elements.kt

@@ -342,6 +342,9 @@ object Elements : TemplateGroupBase() {
         returns("T")
         body {
             """
+            contract {
+                callsInPlace(defaultValue, InvocationKind.AT_MOST_ONCE)
+            }
             if (this is List)
                 return this.getOrElse(index, defaultValue)
             if (index < 0)
@@ -358,6 +361,9 @@ object Elements : TemplateGroupBase() {
         }
         body(Sequences) {
             """
+            contract {
+                callsInPlace(defaultValue, InvocationKind.AT_MOST_ONCE)
+            }
             if (index < 0)
                 return defaultValue(index)
             val iterator = iterator()
@@ -374,6 +380,9 @@ object Elements : TemplateGroupBase() {
             inlineOnly()
             body {
                 """
+                contract {
+                    callsInPlace(defaultValue, InvocationKind.AT_MOST_ONCE)
+                }
                 return if (index >= 0 && index <= lastIndex) get(index) else defaultValue(index)
                 """
             }
@@ -388,6 +397,9 @@ object Elements : TemplateGroupBase() {
         inlineOnly()
         body {
             """
+            contract {
+                callsInPlace(defaultValue, InvocationKind.AT_MOST_ONCE)
+            }
             return if (index >= 0 && index <= lastIndex) get(index) else defaultValue(index)
             """
         }

libraries/tools/kotlin-stdlib-gen/src/templates/dsl/Writers.kt

@@ -105,6 +105,7 @@ fun List<MemberBuilder>.writeTo(file: File, targetedSource: TargetedSourceFile)
             }
         }
         if (target.platform == Platform.Common) {
+            writer.appendLine("import kotlin.contracts.*")
             writer.appendLine("import kotlin.random.*")
         }
         if (sourceFile.packageName == "kotlin.collections") {