github.com/ianlancetaylor/demangle v0.0.0-20250417193237-f615e6bd150b: ASTToString, ErrNotMangledName, Filter

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:golang/github.com/ianlancetaylor/demangle@v0.0.0-20250417193237-f615e6bd150b
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/ianlancetaylor/demangle@v0.0.0-20250417193237-f615e6bd150b
Demonstrate these symbols/APIs:
  - github.com/ianlancetaylor/demangle.ASTToString
  - github.com/ianlancetaylor/demangle.ErrNotMangledName
  - github.com/ianlancetaylor/demangle.Filter
  - github.com/ianlancetaylor/demangle.NoParams
  - github.com/ianlancetaylor/demangle.NoTemplateParams
  - github.com/ianlancetaylor/demangle.ToAST
  - github.com/ianlancetaylor/demangle.ToString

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:fa0056fd3ddfe5d93b738f1036ae1bf8cacbbe2972019afb40a1e71949be5a79","contract":["demangle.ToString demangles basic and qualified C++ symbol names","demangle.ToString with NoParams option suppresses function parameter lists","demangle.ToString with NoTemplateParams option strips template parameter lists","demangle.ToString returns ErrNotMangledName when input is not a C++ mangled name","demangle.Filter returns demangled string for mangled names and unchanged input on errors","demangle.ToAST parses symbol into AST and demangle.ASTToString renders it"],"goal":"verify pkg:golang/github.com/ianlancetaylor/demangle@v0.0.0-20250417193237-f615e6bd150b","kind":"HOW","packages":["pkg:golang/github.com/ianlancetaylor/demangle@v0.0.0-20250417193237-f615e6bd150b"],"schemaVersion":1,"symbols":["github.com/ianlancetaylor/demangle.ASTToString","github.com/ianlancetaylor/demangle.ErrNotMangledName","github.com/ianlancetaylor/demangle.Filter","github.com/ianlancetaylor/demangle.NoParams","github.com/ianlancetaylor/demangle.NoTemplateParams","github.com/ianlancetaylor/demangle.ToAST","github.com/ianlancetaylor/demangle.ToString"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/ianlancetaylor/demangle@v0.0.0-20250417193237-f615e6bd150b"],"schemaVersion":1,"subject":"pkg:golang/github.com/ianlancetaylor/demangle@v0.0.0-20250417193237-f615e6bd150b","symbols":["github.com/ianlancetaylor/demangle.ASTToString","github.com/ianlancetaylor/demangle.ErrNotMangledName","github.com/ianlancetaylor/demangle.Filter","github.com/ianlancetaylor/demangle.NoParams","github.com/ianlancetaylor/demangle.NoTemplateParams","github.com/ianlancetaylor/demangle.ToAST","github.com/ianlancetaylor/demangle.ToString"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/ianlancetaylor/demangle v0.0.0-20250417193237-f615e6bd150b

github.com/ianlancetaylor/demangle v0.0.0-20250417193237-f615e6bd150b h1:ogbOPx86mIhFy764gGkqnkFC8m5PJA7sPzlk9ppLVQA=
github.com/ianlancetaylor/demangle v0.0.0-20250417193237-f615e6bd150b/go.mod h1:gx7rwoVhcfuVKG5uya9Hs3Sxj7EIvldVofAWIUtGouw=

package sample

import (
	"github.com/ianlancetaylor/demangle"
)

// DemangleSymbol demangles a C++ mangled symbol string.
func DemangleSymbol(name string, options ...demangle.Option) (string, error) {
	return demangle.ToString(name, options...)
}

// FilterSymbol demangles a symbol, or returns the original string if not a mangled name.
func FilterSymbol(name string, options ...demangle.Option) string {
	return demangle.Filter(name, options...)
}

// ParseToAST parses a mangled symbol name into an AST and prints it with options.
func ParseToAST(name string, options ...demangle.Option) (demangle.AST, string, error) {
	ast, err := demangle.ToAST(name, options...)
	if err != nil {
		return nil, "", err
	}
	formatted := demangle.ASTToString(ast, options...)
	return ast, formatted, nil
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/ianlancetaylor/demangle@v0.0.0-20250417193237-f615e6bd150b",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/ianlancetaylor/demangle@v0.0.0-20250417193237-f615e6bd150b"
  ],
  "symbols": [
    "github.com/ianlancetaylor/demangle.ASTToString",
    "github.com/ianlancetaylor/demangle.ErrNotMangledName",
    "github.com/ianlancetaylor/demangle.Filter",
    "github.com/ianlancetaylor/demangle.NoParams",
    "github.com/ianlancetaylor/demangle.NoTemplateParams",
    "github.com/ianlancetaylor/demangle.ToAST",
    "github.com/ianlancetaylor/demangle.ToString"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"

	"github.com/ianlancetaylor/demangle"
	"sample"
)

func main() {
	// Assertion 1: demangle.ToString demangles basic and qualified C++ symbol names
	{
		res, err := sample.DemangleSymbol("_Z1fv")
		if err != nil {
			fmt.Fprintf(os.Stderr, "ToString basic failed: %v\n", err)
			os.Exit(1)
		}
		if res != "f()" {
			fmt.Fprintf(os.Stderr, "expected 'f()', got %q\n", res)
			os.Exit(1)
		}

		res, err = sample.DemangleSymbol("_ZN3Foo3barEi")
		if err != nil {
			fmt.Fprintf(os.Stderr, "ToString qualified failed: %v\n", err)
			os.Exit(1)
		}
		if res != "Foo::bar(int)" {
			fmt.Fprintf(os.Stderr, "expected 'Foo::bar(int)', got %q\n", res)
			os.Exit(1)
		}
	}

	// Assertion 2: demangle.ToString with NoParams option suppresses function parameter lists
	{
		res, err := sample.DemangleSymbol("_Z1fi", demangle.NoParams)
		if err != nil {
			fmt.Fprintf(os.Stderr, "ToString NoParams failed: %v\n", err)
			os.Exit(1)
		}
		if res != "f" {
			fmt.Fprintf(os.Stderr, "expected 'f', got %q\n", res)
			os.Exit(1)
		}
	}

	// Assertion 3: demangle.ToString with NoTemplateParams option strips template parameter lists
	{
		res, err := sample.DemangleSymbol("_ZN3FooIfE3barEi", demangle.NoTemplateParams)
		if err != nil {
			fmt.Fprintf(os.Stderr, "ToString NoTemplateParams failed: %v\n", err)
			os.Exit(1)
		}
		if res != "Foo::bar(int)" {
			fmt.Fprintf(os.Stderr, "expected 'Foo::bar(int)', got %q\n", res)
			os.Exit(1)
		}
	}

	// Assertion 4: demangle.ToString returns ErrNotMangledName when input is not a C++ mangled name
	{
		_, err := sample.DemangleSymbol("non_mangled_symbol")
		if err == nil {
			fmt.Fprintf(os.Stderr, "expected ErrNotMangledName for non-mangled input, got nil\n")
			os.Exit(1)
		}
		if !errors.Is(err, demangle.ErrNotMangledName) && err != demangle.ErrNotMangledName {
			fmt.Fprintf(os.Stderr, "expected ErrNotMangledName, got %v\n", err)
			os.Exit(1)
		}
	}

	// Assertion 5: demangle.Filter returns demangled string for mangled names and unchanged input on errors
	{
		demangled := sample.FilterSymbol("_Z1fv")
		if demangled != "f()" {
			fmt.Fprintf(os.Stderr, "Filter demangled expected 'f()', got %q\n", demangled)
			os.Exit(1)
		}

		plain := sample.FilterSymbol("printf")
		if plain != "printf" {
			fmt.Fprintf(os.Stderr, "Filter unchanged expected 'printf', got %q\n", plain)
			os.Exit(1)
		}
	}

	// Assertion 6: demangle.ToAST parses symbol into AST and demangle.ASTToString renders it
	{
		ast, formatted, err := sample.ParseToAST("_Z1fv")
		if err != nil {
			fmt.Fprintf(os.Stderr, "ParseToAST failed: %v\n", err)
			os.Exit(1)
		}
		if ast == nil {
			fmt.Fprintf(os.Stderr, "expected non-nil AST\n")
			os.Exit(1)
		}
		if formatted != "f()" {
			fmt.Fprintf(os.Stderr, "expected ASTToString 'f()', got %q\n", formatted)
			os.Exit(1)
		}
	}

	fmt.Println("All demangle contract assertions passed.")
}