JSSpecCompiler: Elide nested `TreeList` nodes

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/AST.cpp

@@ -83,10 +83,22 @@ Vector<NodeSubtreePointer> IfElseIfChain::subtrees()
     return result;
 }
 
+TreeList::TreeList(Vector<Tree>&& trees)
+{
+    for (auto const& tree : trees) {
+        if (tree->is_list()) {
+            for (auto const& nested_tree : as<TreeList>(tree)->m_trees)
+                m_trees.append(nested_tree);
+        } else {
+            m_trees.append(tree);
+        }
+    }
+}
+
 Vector<NodeSubtreePointer> TreeList::subtrees()
 {
     Vector<NodeSubtreePointer> result;
-    for (auto& expression : m_expressions)
+    for (auto& expression : m_trees)
         result.append({ &expression });
     return result;
 }

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/AST.h

@@ -59,7 +59,7 @@ public:
     // For expressions, order must be the same as the evaluation order.
     virtual Vector<NodeSubtreePointer> subtrees() { return {}; }
 
-    virtual bool is_type() { return false; }
+    virtual bool is_list() const { return false; }
 
 protected:
     template<typename... Parameters>
@@ -372,14 +372,13 @@ protected:
 
 class TreeList : public Statement {
 public:
-    TreeList(Vector<Tree>&& expressions_)
-        : m_expressions(move(expressions_))
-    {
-    }
+    TreeList(Vector<Tree>&& trees);
 
     Vector<NodeSubtreePointer> subtrees() override;
 
-    Vector<Tree> m_expressions;
+    bool is_list() const override { return true; }
+
+    Vector<Tree> m_trees;
 
 protected:
     void dump_tree(StringBuilder& builder) override;

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/ASTPrinting.cpp

@@ -129,7 +129,7 @@ void IfElseIfChain::dump_tree(StringBuilder& builder)
 void TreeList::dump_tree(StringBuilder& builder)
 {
     dump_node(builder, "TreeList");
-    for (auto const& expression : m_expressions)
+    for (auto const& expression : m_trees)
         expression->format_tree(builder);
 }
 

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Compiler/IfBranchMergingPass.cpp

@@ -24,7 +24,7 @@ RecursionDecision IfBranchMergingPass::on_entry(Tree tree)
             }
         };
 
-        for (auto const& node : list->m_expressions) {
+        for (auto const& node : list->m_trees) {
             if (is<IfBranch>(node.ptr())) {
                 merge_if_needed();
                 unmerged_branches.append(node);
@@ -37,7 +37,7 @@ RecursionDecision IfBranchMergingPass::on_entry(Tree tree)
         }
         merge_if_needed();
 
-        list->m_expressions = move(result);
+        list->m_trees = move(result);
     }
     return RecursionDecision::Recurse;
 }
@@ -75,8 +75,8 @@ Tree IfBranchMergingPass::merge_branches(Vector<Tree> const& unmerged_branches)
             //   3. Else,
             //      ...
             auto substep_list = as<TreeList>(branch->m_branch);
-            if (substep_list && substep_list->m_expressions.size() == 1) {
-                if (auto nested_if = as<IfBranch>(substep_list->m_expressions[0]); nested_if)
+            if (substep_list && substep_list->m_trees.size() == 1) {
+                if (auto nested_if = as<IfBranch>(substep_list->m_trees[0]); nested_if)
                     branch = make_ref_counted<ElseIfBranch>(nested_if->m_condition, nested_if->m_branch);
             }
         }