Function optPassMergeVarDeclarations

tools/unsafe_optimizations.mjs:136–159

(ast)

// Finds multiple consecutive VariableDeclaration nodes, and fuses them together.
// 'var a = 1; var b = 2;' -> 'var a = 1, b = 2;'
function optPassMergeVarDeclarations(ast) {
  let progress = false;

  visitNodes(ast, ['BlockStatement', 'Program'], (node) => {
    const nodeArray = node.body;
    for (let i = 0; i < nodeArray.length; ++i) {
      const n = nodeArray[i];
      if (n.type != 'VariableDeclaration') continue;
      // Look back to find if there is a preceding VariableDeclaration that this declaration could be fused to.
      for (let j = i - 1; j >= 0; --j) {
        const p = nodeArray[j];
        if (p.type == 'VariableDeclaration') {
          p.declarations = p.declarations.concat(n.declarations);
          nodeArray.splice(i--, 1);
          progress = true;
          break;
        } else if (!['FunctionDeclaration'].includes(p.type)) {
          break;
        }
      }
    }
  });
  return progress;
}

// Merges "var a,b;a = ...;" to "var b, a = ...;"
function optPassMergeVarInitializationAssignments(ast) {