Had the same issue and resolved after updating the gradle version to
classpath "com.android.tools.build:gradle:4.2.0-alpha14"
and instead of declaring compiler version kotlinCompilerExtensionVersion
in the composeoptions, decalred as a dependency
implementation "androidx.ui:ui-tooling:$compose_version"
implementation "androidx.compose.runtime:runtime:$compose_version"
implementation "androidx.compose.compiler:compiler:$compose_version"