rust/crates/ide-assists/src/utils.rs
2023-01-23 00:22:46 +09:00

765 lines
26 KiB
Rust

//! Assorted functions shared by several assists.
use std::ops;
pub(crate) use gen_trait_fn_body::gen_trait_fn_body;
use hir::{db::HirDatabase, HirDisplay, Semantics};
use ide_db::{famous_defs::FamousDefs, path_transform::PathTransform, RootDatabase, SnippetCap};
use stdx::format_to;
use syntax::{
ast::{
self,
edit::{self, AstNodeEdit},
edit_in_place::{AttrsOwnerEdit, Removable},
make, HasArgList, HasAttrs, HasGenericParams, HasName, HasTypeBounds, Whitespace,
},
ted, AstNode, AstToken, Direction, SourceFile,
SyntaxKind::*,
SyntaxNode, TextRange, TextSize, T,
};
use crate::assist_context::{AssistContext, SourceChangeBuilder};
pub(crate) mod suggest_name;
mod gen_trait_fn_body;
pub(crate) fn unwrap_trivial_block(block_expr: ast::BlockExpr) -> ast::Expr {
extract_trivial_expression(&block_expr)
.filter(|expr| !expr.syntax().text().contains_char('\n'))
.unwrap_or_else(|| block_expr.into())
}
pub fn extract_trivial_expression(block_expr: &ast::BlockExpr) -> Option<ast::Expr> {
if block_expr.modifier().is_some() {
return None;
}
let stmt_list = block_expr.stmt_list()?;
let has_anything_else = |thing: &SyntaxNode| -> bool {
let mut non_trivial_children =
stmt_list.syntax().children_with_tokens().filter(|it| match it.kind() {
WHITESPACE | T!['{'] | T!['}'] => false,
_ => it.as_node() != Some(thing),
});
non_trivial_children.next().is_some()
};
if let Some(expr) = stmt_list.tail_expr() {
if has_anything_else(expr.syntax()) {
return None;
}
return Some(expr);
}
// Unwrap `{ continue; }`
let stmt = stmt_list.statements().next()?;
if let ast::Stmt::ExprStmt(expr_stmt) = stmt {
if has_anything_else(expr_stmt.syntax()) {
return None;
}
let expr = expr_stmt.expr()?;
if matches!(expr.syntax().kind(), CONTINUE_EXPR | BREAK_EXPR | RETURN_EXPR) {
return Some(expr);
}
}
None
}
/// This is a method with a heuristics to support test methods annotated with custom test annotations, such as
/// `#[test_case(...)]`, `#[tokio::test]` and similar.
/// Also a regular `#[test]` annotation is supported.
///
/// It may produce false positives, for example, `#[wasm_bindgen_test]` requires a different command to run the test,
/// but it's better than not to have the runnables for the tests at all.
pub fn test_related_attribute(fn_def: &ast::Fn) -> Option<ast::Attr> {
fn_def.attrs().find_map(|attr| {
let path = attr.path()?;
let text = path.syntax().text().to_string();
if text.starts_with("test") || text.ends_with("test") {
Some(attr)
} else {
None
}
})
}
#[derive(Copy, Clone, PartialEq)]
pub enum DefaultMethods {
Only,
No,
}
pub fn filter_assoc_items(
sema: &Semantics<'_, RootDatabase>,
items: &[hir::AssocItem],
default_methods: DefaultMethods,
) -> Vec<ast::AssocItem> {
fn has_def_name(item: &ast::AssocItem) -> bool {
match item {
ast::AssocItem::Fn(def) => def.name(),
ast::AssocItem::TypeAlias(def) => def.name(),
ast::AssocItem::Const(def) => def.name(),
ast::AssocItem::MacroCall(_) => None,
}
.is_some()
}
items
.iter()
// Note: This throws away items with no source.
.filter_map(|&i| {
let item = match i {
hir::AssocItem::Function(i) => ast::AssocItem::Fn(sema.source(i)?.value),
hir::AssocItem::TypeAlias(i) => ast::AssocItem::TypeAlias(sema.source(i)?.value),
hir::AssocItem::Const(i) => ast::AssocItem::Const(sema.source(i)?.value),
};
Some(item)
})
.filter(has_def_name)
.filter(|it| match it {
ast::AssocItem::Fn(def) => matches!(
(default_methods, def.body()),
(DefaultMethods::Only, Some(_)) | (DefaultMethods::No, None)
),
ast::AssocItem::Const(def) => matches!(
(default_methods, def.body()),
(DefaultMethods::Only, Some(_)) | (DefaultMethods::No, None)
),
_ => default_methods == DefaultMethods::No,
})
.collect::<Vec<_>>()
}
pub fn add_trait_assoc_items_to_impl(
sema: &Semantics<'_, RootDatabase>,
items: Vec<ast::AssocItem>,
trait_: hir::Trait,
impl_: ast::Impl,
target_scope: hir::SemanticsScope<'_>,
) -> (ast::Impl, ast::AssocItem) {
let source_scope = sema.scope_for_def(trait_);
let transform = PathTransform::trait_impl(&target_scope, &source_scope, trait_, impl_.clone());
let items = items.into_iter().map(|assoc_item| {
transform.apply(assoc_item.syntax());
assoc_item.remove_attrs_and_docs();
assoc_item
});
let res = impl_.clone_for_update();
let assoc_item_list = res.get_or_create_assoc_item_list();
let mut first_item = None;
for item in items {
first_item.get_or_insert_with(|| item.clone());
match &item {
ast::AssocItem::Fn(fn_) if fn_.body().is_none() => {
let body = make::block_expr(None, Some(make::ext::expr_todo()))
.indent(edit::IndentLevel(1));
ted::replace(fn_.get_or_create_body().syntax(), body.clone_for_update().syntax())
}
ast::AssocItem::TypeAlias(type_alias) => {
if let Some(type_bound_list) = type_alias.type_bound_list() {
type_bound_list.remove()
}
}
_ => {}
}
assoc_item_list.add_item(item)
}
(res, first_item.unwrap())
}
#[derive(Clone, Copy, Debug)]
pub(crate) enum Cursor<'a> {
Replace(&'a SyntaxNode),
Before(&'a SyntaxNode),
}
impl<'a> Cursor<'a> {
fn node(self) -> &'a SyntaxNode {
match self {
Cursor::Replace(node) | Cursor::Before(node) => node,
}
}
}
pub(crate) fn render_snippet(_cap: SnippetCap, node: &SyntaxNode, cursor: Cursor<'_>) -> String {
assert!(cursor.node().ancestors().any(|it| it == *node));
let range = cursor.node().text_range() - node.text_range().start();
let range: ops::Range<usize> = range.into();
let mut placeholder = cursor.node().to_string();
escape(&mut placeholder);
let tab_stop = match cursor {
Cursor::Replace(placeholder) => format!("${{0:{placeholder}}}"),
Cursor::Before(placeholder) => format!("$0{placeholder}"),
};
let mut buf = node.to_string();
buf.replace_range(range, &tab_stop);
return buf;
fn escape(buf: &mut String) {
stdx::replace(buf, '{', r"\{");
stdx::replace(buf, '}', r"\}");
stdx::replace(buf, '$', r"\$");
}
}
pub(crate) fn vis_offset(node: &SyntaxNode) -> TextSize {
node.children_with_tokens()
.find(|it| !matches!(it.kind(), WHITESPACE | COMMENT | ATTR))
.map(|it| it.text_range().start())
.unwrap_or_else(|| node.text_range().start())
}
pub(crate) fn invert_boolean_expression(expr: ast::Expr) -> ast::Expr {
invert_special_case(&expr).unwrap_or_else(|| make::expr_prefix(T![!], expr))
}
fn invert_special_case(expr: &ast::Expr) -> Option<ast::Expr> {
match expr {
ast::Expr::BinExpr(bin) => {
let bin = bin.clone_for_update();
let op_token = bin.op_token()?;
let rev_token = match op_token.kind() {
T![==] => T![!=],
T![!=] => T![==],
T![<] => T![>=],
T![<=] => T![>],
T![>] => T![<=],
T![>=] => T![<],
// Parenthesize other expressions before prefixing `!`
_ => return Some(make::expr_prefix(T![!], make::expr_paren(expr.clone()))),
};
ted::replace(op_token, make::token(rev_token));
Some(bin.into())
}
ast::Expr::MethodCallExpr(mce) => {
let receiver = mce.receiver()?;
let method = mce.name_ref()?;
let arg_list = mce.arg_list()?;
let method = match method.text().as_str() {
"is_some" => "is_none",
"is_none" => "is_some",
"is_ok" => "is_err",
"is_err" => "is_ok",
_ => return None,
};
Some(make::expr_method_call(receiver, make::name_ref(method), arg_list))
}
ast::Expr::PrefixExpr(pe) if pe.op_kind()? == ast::UnaryOp::Not => match pe.expr()? {
ast::Expr::ParenExpr(parexpr) => parexpr.expr(),
_ => pe.expr(),
},
ast::Expr::Literal(lit) => match lit.kind() {
ast::LiteralKind::Bool(b) => match b {
true => Some(ast::Expr::Literal(make::expr_literal("false"))),
false => Some(ast::Expr::Literal(make::expr_literal("true"))),
},
_ => None,
},
_ => None,
}
}
pub(crate) fn next_prev() -> impl Iterator<Item = Direction> {
[Direction::Next, Direction::Prev].into_iter()
}
pub(crate) fn does_pat_match_variant(pat: &ast::Pat, var: &ast::Pat) -> bool {
let first_node_text = |pat: &ast::Pat| pat.syntax().first_child().map(|node| node.text());
let pat_head = match pat {
ast::Pat::IdentPat(bind_pat) => match bind_pat.pat() {
Some(p) => first_node_text(&p),
None => return pat.syntax().text() == var.syntax().text(),
},
pat => first_node_text(pat),
};
let var_head = first_node_text(var);
pat_head == var_head
}
pub(crate) fn does_nested_pattern(pat: &ast::Pat) -> bool {
let depth = calc_depth(pat, 0);
if 1 < depth {
return true;
}
false
}
fn calc_depth(pat: &ast::Pat, depth: usize) -> usize {
match pat {
ast::Pat::IdentPat(_)
| ast::Pat::BoxPat(_)
| ast::Pat::RestPat(_)
| ast::Pat::LiteralPat(_)
| ast::Pat::MacroPat(_)
| ast::Pat::OrPat(_)
| ast::Pat::ParenPat(_)
| ast::Pat::PathPat(_)
| ast::Pat::WildcardPat(_)
| ast::Pat::RangePat(_)
| ast::Pat::RecordPat(_)
| ast::Pat::RefPat(_)
| ast::Pat::SlicePat(_)
| ast::Pat::TuplePat(_)
| ast::Pat::ConstBlockPat(_) => depth,
// FIXME: Other patterns may also be nested. Currently it simply supports only `TupleStructPat`
ast::Pat::TupleStructPat(pat) => {
let mut max_depth = depth;
for p in pat.fields() {
let d = calc_depth(&p, depth + 1);
if d > max_depth {
max_depth = d
}
}
max_depth
}
}
}
// Uses a syntax-driven approach to find any impl blocks for the struct that
// exist within the module/file
//
// Returns `None` if we've found an existing fn
//
// FIXME: change the new fn checking to a more semantic approach when that's more
// viable (e.g. we process proc macros, etc)
// FIXME: this partially overlaps with `find_impl_block_*`
/// `find_struct_impl` looks for impl of a struct, but this also has additional feature
/// where it takes a list of function names and check if they exist inside impl_, if
/// even one match is found, it returns None
pub(crate) fn find_struct_impl(
ctx: &AssistContext<'_>,
adt: &ast::Adt,
names: &[String],
) -> Option<Option<ast::Impl>> {
let db = ctx.db();
let module = adt.syntax().parent()?;
let struct_def = ctx.sema.to_def(adt)?;
let block = module.descendants().filter_map(ast::Impl::cast).find_map(|impl_blk| {
let blk = ctx.sema.to_def(&impl_blk)?;
// FIXME: handle e.g. `struct S<T>; impl<U> S<U> {}`
// (we currently use the wrong type parameter)
// also we wouldn't want to use e.g. `impl S<u32>`
let same_ty = match blk.self_ty(db).as_adt() {
Some(def) => def == struct_def,
None => false,
};
let not_trait_impl = blk.trait_(db).is_none();
if !(same_ty && not_trait_impl) {
None
} else {
Some(impl_blk)
}
});
if let Some(ref impl_blk) = block {
if has_any_fn(impl_blk, names) {
return None;
}
}
Some(block)
}
fn has_any_fn(imp: &ast::Impl, names: &[String]) -> bool {
if let Some(il) = imp.assoc_item_list() {
for item in il.assoc_items() {
if let ast::AssocItem::Fn(f) = item {
if let Some(name) = f.name() {
if names.iter().any(|n| n.eq_ignore_ascii_case(&name.text())) {
return true;
}
}
}
}
}
false
}
/// Find the start of the `impl` block for the given `ast::Impl`.
//
// FIXME: this partially overlaps with `find_struct_impl`
pub(crate) fn find_impl_block_start(impl_def: ast::Impl, buf: &mut String) -> Option<TextSize> {
buf.push('\n');
let start = impl_def.assoc_item_list().and_then(|it| it.l_curly_token())?.text_range().end();
Some(start)
}
/// Find the end of the `impl` block for the given `ast::Impl`.
//
// FIXME: this partially overlaps with `find_struct_impl`
pub(crate) fn find_impl_block_end(impl_def: ast::Impl, buf: &mut String) -> Option<TextSize> {
buf.push('\n');
let end = impl_def
.assoc_item_list()
.and_then(|it| it.r_curly_token())?
.prev_sibling_or_token()?
.text_range()
.end();
Some(end)
}
/// Generates the surrounding `impl Type { <code> }` including type and lifetime
/// parameters.
pub(crate) fn generate_impl_text(adt: &ast::Adt, code: &str) -> String {
generate_impl_text_inner(adt, None, true, code)
}
/// Generates the surrounding `impl <trait> for Type { <code> }` including type
/// and lifetime parameters, with `<trait>` appended to `impl`'s generic parameters' bounds.
///
/// This is useful for traits like `PartialEq`, since `impl<T> PartialEq for U<T>` often requires `T: PartialEq`.
pub(crate) fn generate_trait_impl_text(adt: &ast::Adt, trait_text: &str, code: &str) -> String {
generate_impl_text_inner(adt, Some(trait_text), true, code)
}
/// Generates the surrounding `impl <trait> for Type { <code> }` including type
/// and lifetime parameters, with `impl`'s generic parameters' bounds kept as-is.
///
/// This is useful for traits like `From<T>`, since `impl<T> From<T> for U<T>` doesn't require `T: From<T>`.
pub(crate) fn generate_trait_impl_text_intransitive(
adt: &ast::Adt,
trait_text: &str,
code: &str,
) -> String {
generate_impl_text_inner(adt, Some(trait_text), false, code)
}
fn generate_impl_text_inner(
adt: &ast::Adt,
trait_text: Option<&str>,
trait_is_transitive: bool,
code: &str,
) -> String {
// Ensure lifetime params are before type & const params
let generic_params = adt.generic_param_list().map(|generic_params| {
let lifetime_params =
generic_params.lifetime_params().map(ast::GenericParam::LifetimeParam);
let ty_or_const_params = generic_params.type_or_const_params().map(|param| {
match param {
ast::TypeOrConstParam::Type(param) => {
let param = param.clone_for_update();
// remove defaults since they can't be specified in impls
param.remove_default();
let mut bounds =
param.type_bound_list().map_or_else(Vec::new, |it| it.bounds().collect());
if let Some(trait_) = trait_text {
// Add the current trait to `bounds` if the trait is transitive,
// meaning `impl<T> Trait for U<T>` requires `T: Trait`.
if trait_is_transitive {
bounds.push(make::type_bound(trait_));
}
};
// `{ty_param}: {bounds}`
let param =
make::type_param(param.name().unwrap(), make::type_bound_list(bounds));
ast::GenericParam::TypeParam(param)
}
ast::TypeOrConstParam::Const(param) => {
let param = param.clone_for_update();
// remove defaults since they can't be specified in impls
param.remove_default();
ast::GenericParam::ConstParam(param)
}
}
});
make::generic_param_list(itertools::chain(lifetime_params, ty_or_const_params))
});
// FIXME: use syntax::make & mutable AST apis instead
// `trait_text` and `code` can't be opaque blobs of text
let mut buf = String::with_capacity(code.len());
// Copy any cfg attrs from the original adt
buf.push_str("\n\n");
let cfg_attrs = adt
.attrs()
.filter(|attr| attr.as_simple_call().map(|(name, _arg)| name == "cfg").unwrap_or(false));
cfg_attrs.for_each(|attr| buf.push_str(&format!("{attr}\n")));
// `impl{generic_params} {trait_text} for {name}{generic_params.to_generic_args()}`
buf.push_str("impl");
if let Some(generic_params) = &generic_params {
format_to!(buf, "{generic_params}");
}
buf.push(' ');
if let Some(trait_text) = trait_text {
buf.push_str(trait_text);
buf.push_str(" for ");
}
buf.push_str(&adt.name().unwrap().text());
if let Some(generic_params) = generic_params {
format_to!(buf, "{}", generic_params.to_generic_args());
}
match adt.where_clause() {
Some(where_clause) => {
format_to!(buf, "\n{where_clause}\n{{\n{code}\n}}");
}
None => {
format_to!(buf, " {{\n{code}\n}}");
}
}
buf
}
pub(crate) fn add_method_to_adt(
builder: &mut SourceChangeBuilder,
adt: &ast::Adt,
impl_def: Option<ast::Impl>,
method: &str,
) {
let mut buf = String::with_capacity(method.len() + 2);
if impl_def.is_some() {
buf.push('\n');
}
buf.push_str(method);
let start_offset = impl_def
.and_then(|impl_def| find_impl_block_end(impl_def, &mut buf))
.unwrap_or_else(|| {
buf = generate_impl_text(adt, &buf);
adt.syntax().text_range().end()
});
builder.insert(start_offset, buf);
}
#[derive(Debug)]
pub(crate) struct ReferenceConversion {
conversion: ReferenceConversionType,
ty: hir::Type,
}
#[derive(Debug)]
enum ReferenceConversionType {
// reference can be stripped if the type is Copy
Copy,
// &String -> &str
AsRefStr,
// &Vec<T> -> &[T]
AsRefSlice,
// &Box<T> -> &T
Dereferenced,
// &Option<T> -> Option<&T>
Option,
// &Result<T, E> -> Result<&T, &E>
Result,
}
impl ReferenceConversion {
pub(crate) fn convert_type(&self, db: &dyn HirDatabase) -> String {
match self.conversion {
ReferenceConversionType::Copy => self.ty.display(db).to_string(),
ReferenceConversionType::AsRefStr => "&str".to_string(),
ReferenceConversionType::AsRefSlice => {
let type_argument_name =
self.ty.type_arguments().next().unwrap().display(db).to_string();
format!("&[{type_argument_name}]")
}
ReferenceConversionType::Dereferenced => {
let type_argument_name =
self.ty.type_arguments().next().unwrap().display(db).to_string();
format!("&{type_argument_name}")
}
ReferenceConversionType::Option => {
let type_argument_name =
self.ty.type_arguments().next().unwrap().display(db).to_string();
format!("Option<&{type_argument_name}>")
}
ReferenceConversionType::Result => {
let mut type_arguments = self.ty.type_arguments();
let first_type_argument_name =
type_arguments.next().unwrap().display(db).to_string();
let second_type_argument_name =
type_arguments.next().unwrap().display(db).to_string();
format!("Result<&{first_type_argument_name}, &{second_type_argument_name}>")
}
}
}
pub(crate) fn getter(&self, field_name: String) -> String {
match self.conversion {
ReferenceConversionType::Copy => format!("self.{field_name}"),
ReferenceConversionType::AsRefStr
| ReferenceConversionType::AsRefSlice
| ReferenceConversionType::Dereferenced
| ReferenceConversionType::Option
| ReferenceConversionType::Result => format!("self.{field_name}.as_ref()"),
}
}
}
// FIXME: It should return a new hir::Type, but currently constructing new types is too cumbersome
// and all users of this function operate on string type names, so they can do the conversion
// itself themselves.
pub(crate) fn convert_reference_type(
ty: hir::Type,
db: &RootDatabase,
famous_defs: &FamousDefs<'_, '_>,
) -> Option<ReferenceConversion> {
handle_copy(&ty, db)
.or_else(|| handle_as_ref_str(&ty, db, famous_defs))
.or_else(|| handle_as_ref_slice(&ty, db, famous_defs))
.or_else(|| handle_dereferenced(&ty, db, famous_defs))
.or_else(|| handle_option_as_ref(&ty, db, famous_defs))
.or_else(|| handle_result_as_ref(&ty, db, famous_defs))
.map(|conversion| ReferenceConversion { ty, conversion })
}
fn handle_copy(ty: &hir::Type, db: &dyn HirDatabase) -> Option<ReferenceConversionType> {
ty.is_copy(db).then_some(ReferenceConversionType::Copy)
}
fn handle_as_ref_str(
ty: &hir::Type,
db: &dyn HirDatabase,
famous_defs: &FamousDefs<'_, '_>,
) -> Option<ReferenceConversionType> {
let str_type = hir::BuiltinType::str().ty(db);
ty.impls_trait(db, famous_defs.core_convert_AsRef()?, &[str_type])
.then_some(ReferenceConversionType::AsRefStr)
}
fn handle_as_ref_slice(
ty: &hir::Type,
db: &dyn HirDatabase,
famous_defs: &FamousDefs<'_, '_>,
) -> Option<ReferenceConversionType> {
let type_argument = ty.type_arguments().next()?;
let slice_type = hir::Type::new_slice(type_argument);
ty.impls_trait(db, famous_defs.core_convert_AsRef()?, &[slice_type])
.then_some(ReferenceConversionType::AsRefSlice)
}
fn handle_dereferenced(
ty: &hir::Type,
db: &dyn HirDatabase,
famous_defs: &FamousDefs<'_, '_>,
) -> Option<ReferenceConversionType> {
let type_argument = ty.type_arguments().next()?;
ty.impls_trait(db, famous_defs.core_convert_AsRef()?, &[type_argument])
.then_some(ReferenceConversionType::Dereferenced)
}
fn handle_option_as_ref(
ty: &hir::Type,
db: &dyn HirDatabase,
famous_defs: &FamousDefs<'_, '_>,
) -> Option<ReferenceConversionType> {
if ty.as_adt() == famous_defs.core_option_Option()?.ty(db).as_adt() {
Some(ReferenceConversionType::Option)
} else {
None
}
}
fn handle_result_as_ref(
ty: &hir::Type,
db: &dyn HirDatabase,
famous_defs: &FamousDefs<'_, '_>,
) -> Option<ReferenceConversionType> {
if ty.as_adt() == famous_defs.core_result_Result()?.ty(db).as_adt() {
Some(ReferenceConversionType::Result)
} else {
None
}
}
pub(crate) fn get_methods(items: &ast::AssocItemList) -> Vec<ast::Fn> {
items
.assoc_items()
.flat_map(|i| match i {
ast::AssocItem::Fn(f) => Some(f),
_ => None,
})
.filter(|f| f.name().is_some())
.collect()
}
/// Trim(remove leading and trailing whitespace) `initial_range` in `source_file`, return the trimmed range.
pub(crate) fn trimmed_text_range(source_file: &SourceFile, initial_range: TextRange) -> TextRange {
let mut trimmed_range = initial_range;
while source_file
.syntax()
.token_at_offset(trimmed_range.start())
.find_map(Whitespace::cast)
.is_some()
&& trimmed_range.start() < trimmed_range.end()
{
let start = trimmed_range.start() + TextSize::from(1);
trimmed_range = TextRange::new(start, trimmed_range.end());
}
while source_file
.syntax()
.token_at_offset(trimmed_range.end())
.find_map(Whitespace::cast)
.is_some()
&& trimmed_range.start() < trimmed_range.end()
{
let end = trimmed_range.end() - TextSize::from(1);
trimmed_range = TextRange::new(trimmed_range.start(), end);
}
trimmed_range
}
/// Convert a list of function params to a list of arguments that can be passed
/// into a function call.
pub(crate) fn convert_param_list_to_arg_list(list: ast::ParamList) -> ast::ArgList {
let mut args = vec![];
for param in list.params() {
if let Some(ast::Pat::IdentPat(pat)) = param.pat() {
if let Some(name) = pat.name() {
let name = name.to_string();
let expr = make::expr_path(make::ext::ident_path(&name));
args.push(expr);
}
}
}
make::arg_list(args)
}
/// Calculate the number of hashes required for a raw string containing `s`
pub(crate) fn required_hashes(s: &str) -> usize {
let mut res = 0usize;
for idx in s.match_indices('"').map(|(i, _)| i) {
let (_, sub) = s.split_at(idx + 1);
let n_hashes = sub.chars().take_while(|c| *c == '#').count();
res = res.max(n_hashes + 1)
}
res
}
#[test]
fn test_required_hashes() {
assert_eq!(0, required_hashes("abc"));
assert_eq!(0, required_hashes("###"));
assert_eq!(1, required_hashes("\""));
assert_eq!(2, required_hashes("\"#abc"));
assert_eq!(0, required_hashes("#abc"));
assert_eq!(3, required_hashes("#ab\"##c"));
assert_eq!(5, required_hashes("#ab\"##\"####c"));
}