11 function link(ast) {  argument
12   assert(ast.type === 'Block', 'The top level element should always be a block');
14   if (ast.nodes.length) {
15     var hasExtends = ast.nodes[0].type === 'Extends';
16     checkExtendPosition(ast, hasExtends);
18       extendsNode = ast.nodes.shift();
21   ast = applyIncludes(ast);
22   ast.declaredBlocks = findDeclaredBlocks(ast);
26     ast.nodes.forEach(function addNode(node) {
37     var parent = link(extendsNode.file.ast);
38     extend(parent.declaredBlocks, ast);
54     Object.keys(ast.declaredBlocks).forEach(function (name) {
55       parent.declaredBlocks[name] = ast.declaredBlocks[name];
61   return ast;
64 function findDeclaredBlocks(ast) /*: {[name: string]: Array<BlockNode>}*/ {  argument
66   walk(ast, function before(node) {
86 function extend(parentBlocks, ast) {  argument
88   walk(ast, function before(node) {
119 function applyIncludes(ast, child) {  argument
120   return walk(ast, function before(node, replace) {
126       var childAST = link(node.file.ast);
134 function removeBlocks(ast) {  argument
135   return walk(ast, function (node, replace) {
145 function applyYield(ast, block) {  argument
146   if (!block || !block.nodes.length) return ast;
148   ast = walk(ast, null, function (node, replace) {
169     defaultYieldLocation(ast).nodes.push(block);
171   return ast;
174 function checkExtendPosition(ast, hasExtends) {  argument
176   walk(ast, function (node) {