[FIR generator] Write kDocs for accept & transform methods in FirElement

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/FirElement.kt

@@ -19,18 +19,53 @@ import org.jetbrains.kotlin.fir.visitors.FirVisitorVoid
 interface FirElement {
     val source: KtSourceElement?
 
+    /**
+     * Runs the provided [visitor] on the FIR subtree with the root at this node.
+     *
+     * @param visitor The visitor to accept.
+     * @param data An arbitrary context to pass to each invocation of [visitor]'s methods.
+     * @return The value returned by the topmost `visit*` invocation.
+     */
     fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R =
         visitor.visitElement(this, data)
 
+    /**
+     * Runs the provided [transformer] on the FIR subtree with the root at this node.
+     *
+     * @param transformer The transformer to use.
+     * @param data An arbitrary context to pass to each invocation of [transformer]'s methods.
+     * @return The transformed node.
+     */
     @Suppress("UNCHECKED_CAST")
     fun <E : FirElement, D> transform(transformer: FirTransformer<D>, data: D): E =
         transformer.transformElement(this, data) as E
 
     fun accept(visitor: FirVisitorVoid) = accept(visitor, null)
 
+    /**
+     * Runs the provided [visitor] on subtrees with roots in this node's children.
+     *
+     * Basically, calls `accept(visitor, data)` on each child of this node.
+     *
+     * Does **not** run [visitor] on this node itself.
+     *
+     * @param visitor The visitor for children to accept.
+     * @param data An arbitrary context to pass to each invocation of [visitor]'s methods.
+     */
     fun <R, D> acceptChildren(visitor: FirVisitor<R, D>, data: D)
 
     fun acceptChildren(visitor: FirVisitorVoid) = acceptChildren(visitor, null)
 
+    /**
+     * Recursively transforms this node's children *in place* using [transformer].
+     *
+     * Basically, executes `this.child = this.child.transform(transformer, data)` for each child of this node.
+     *
+     * Does **not** run [transformer] on this node itself.
+     *
+     * @param transformer The transformer to use for transforming the children.
+     * @param data An arbitrary context to pass to each invocation of [transformer]'s methods.
+     * @return `this`
+     */
     fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirElement
 }