convertClassMethod.js

var traverse = require("@babel/traverse").default;
var t = require("@babel/types");

function convert(ast) {
  traverse(ast, {
    ClassMethod(path) {
      const node = path.node;
      node.type = "MethodDefinition";
      node.value = t.functionExpression(null, node.params, node.body, node.generator, node.async);
      node.value.returnType = node.returnType
      node.value.typeParameters = node.typeParameters

      node.value.start = node.start + node.key.name.length;
      node.value.end = node.end;
      node.value.loc = {
        start: {
          line: node.loc.start.line,
          column: 0,
        },
        end: {
          line: node.loc.end.line,
          column: node.loc.end.column,
        }
      };
    }
  });
}