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sugg.rs
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sugg.rs
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//! Contains utility functions to generate suggestions.
#![deny(missing_docs_in_private_items)]
// currently ignores lifetimes and generics
#![allow(use_self)]
use matches::matches;
use rustc::hir;
use rustc::lint::{EarlyContext, LateContext, LintContext};
use rustc_errors;
use std::borrow::Cow;
use std::fmt::Display;
use std;
use syntax::source_map::{CharPos, Span};
use syntax::parse::token;
use syntax::print::pprust::token_to_string;
use syntax::util::parser::AssocOp;
use syntax::ast;
use crate::utils::{higher, snippet, snippet_opt};
use syntax_pos::{BytePos, Pos};
/// A helper type to build suggestion correctly handling parenthesis.
pub enum Sugg<'a> {
/// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
NonParen(Cow<'a, str>),
/// An expression that does not fit in other variants.
MaybeParen(Cow<'a, str>),
/// A binary operator expression, including `as`-casts and explicit type
/// coercion.
BinOp(AssocOp, Cow<'a, str>),
}
/// Literal constant `1`, for convenience.
pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
impl Display for Sugg<'_> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
match *self {
Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) | Sugg::BinOp(_, ref s) => s.fmt(f),
}
}
}
#[allow(wrong_self_convention)] // ok, because of the function `as_ty` method
impl<'a> Sugg<'a> {
/// Prepare a suggestion from an expression.
pub fn hir_opt(cx: &LateContext<'_, '_>, expr: &hir::Expr) -> Option<Self> {
snippet_opt(cx, expr.span).map(|snippet| {
let snippet = Cow::Owned(snippet);
match expr.node {
hir::ExprKind::AddrOf(..) |
hir::ExprKind::Box(..) |
hir::ExprKind::Closure(.., _) |
hir::ExprKind::If(..) |
hir::ExprKind::Unary(..) |
hir::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
hir::ExprKind::Continue(..) |
hir::ExprKind::Yield(..) |
hir::ExprKind::Array(..) |
hir::ExprKind::Block(..) |
hir::ExprKind::Break(..) |
hir::ExprKind::Call(..) |
hir::ExprKind::Field(..) |
hir::ExprKind::Index(..) |
hir::ExprKind::InlineAsm(..) |
hir::ExprKind::Lit(..) |
hir::ExprKind::Loop(..) |
hir::ExprKind::MethodCall(..) |
hir::ExprKind::Path(..) |
hir::ExprKind::Repeat(..) |
hir::ExprKind::Ret(..) |
hir::ExprKind::Struct(..) |
hir::ExprKind::Tup(..) |
hir::ExprKind::While(..) => Sugg::NonParen(snippet),
hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
}
})
}
/// Convenience function around `hir_opt` for suggestions with a default
/// text.
pub fn hir(cx: &LateContext<'_, '_>, expr: &hir::Expr, default: &'a str) -> Self {
Self::hir_opt(cx, expr).unwrap_or_else(|| Sugg::NonParen(Cow::Borrowed(default)))
}
/// Prepare a suggestion from an expression.
pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
use syntax::ast::RangeLimits;
let snippet = snippet(cx, expr.span, default);
match expr.node {
ast::ExprKind::AddrOf(..) |
ast::ExprKind::Box(..) |
ast::ExprKind::Closure(..) |
ast::ExprKind::If(..) |
ast::ExprKind::IfLet(..) |
ast::ExprKind::ObsoleteInPlace(..) |
ast::ExprKind::Unary(..) |
ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
ast::ExprKind::Async(..) |
ast::ExprKind::Block(..) |
ast::ExprKind::Break(..) |
ast::ExprKind::Call(..) |
ast::ExprKind::Continue(..) |
ast::ExprKind::Yield(..) |
ast::ExprKind::Field(..) |
ast::ExprKind::ForLoop(..) |
ast::ExprKind::Index(..) |
ast::ExprKind::InlineAsm(..) |
ast::ExprKind::Lit(..) |
ast::ExprKind::Loop(..) |
ast::ExprKind::Mac(..) |
ast::ExprKind::MethodCall(..) |
ast::ExprKind::Paren(..) |
ast::ExprKind::Path(..) |
ast::ExprKind::Repeat(..) |
ast::ExprKind::Ret(..) |
ast::ExprKind::Struct(..) |
ast::ExprKind::Try(..) |
ast::ExprKind::TryBlock(..) |
ast::ExprKind::Tup(..) |
ast::ExprKind::Array(..) |
ast::ExprKind::While(..) |
ast::ExprKind::WhileLet(..) => Sugg::NonParen(snippet),
ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
}
}
/// Convenience method to create the `<lhs> && <rhs>` suggestion.
pub fn and(self, rhs: &Self) -> Sugg<'static> {
make_binop(ast::BinOpKind::And, &self, rhs)
}
/// Convenience method to create the `<lhs> as <rhs>` suggestion.
pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
}
/// Convenience method to create the `&<expr>` suggestion.
pub fn addr(self) -> Sugg<'static> {
make_unop("&", self)
}
/// Convenience method to create the `&mut <expr>` suggestion.
pub fn mut_addr(self) -> Sugg<'static> {
make_unop("&mut ", self)
}
/// Convenience method to create the `*<expr>` suggestion.
pub fn deref(self) -> Sugg<'static> {
make_unop("*", self)
}
/// Convenience method to create the `&*<expr>` suggestion. Currently this
/// is needed because `sugg.deref().addr()` produces an unnecessary set of
/// parentheses around the deref.
pub fn addr_deref(self) -> Sugg<'static> {
make_unop("&*", self)
}
/// Convenience method to create the `&mut *<expr>` suggestion. Currently
/// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
/// set of parentheses around the deref.
pub fn mut_addr_deref(self) -> Sugg<'static> {
make_unop("&mut *", self)
}
/// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
/// suggestion.
pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
match limit {
ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
}
}
/// Add parenthesis to any expression that might need them. Suitable to the
/// `self` argument of
/// a method call (eg. to build `bar.foo()` or `(1 + 2).foo()`).
pub fn maybe_par(self) -> Self {
match self {
Sugg::NonParen(..) => self,
// (x) and (x).y() both don't need additional parens
Sugg::MaybeParen(sugg) => if sugg.starts_with('(') && sugg.ends_with(')') {
Sugg::MaybeParen(sugg)
} else {
Sugg::NonParen(format!("({})", sugg).into())
},
Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
}
}
}
impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
type Output = Sugg<'static>;
fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
make_binop(ast::BinOpKind::Add, &self, &rhs)
}
}
impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
type Output = Sugg<'static>;
fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
make_binop(ast::BinOpKind::Sub, &self, &rhs)
}
}
impl<'a> std::ops::Not for Sugg<'a> {
type Output = Sugg<'static>;
fn not(self) -> Sugg<'static> {
make_unop("!", self)
}
}
/// Helper type to display either `foo` or `(foo)`.
struct ParenHelper<T> {
/// Whether parenthesis are needed.
paren: bool,
/// The main thing to display.
wrapped: T,
}
impl<T> ParenHelper<T> {
/// Build a `ParenHelper`.
fn new(paren: bool, wrapped: T) -> Self {
Self {
paren,
wrapped,
}
}
}
impl<T: Display> Display for ParenHelper<T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
if self.paren {
write!(f, "({})", self.wrapped)
} else {
self.wrapped.fmt(f)
}
}
}
/// Build the string for `<op><expr>` adding parenthesis when necessary.
///
/// For convenience, the operator is taken as a string because all unary
/// operators have the same
/// precedence.
pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
}
/// Build the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
///
/// Precedence of shift operator relative to other arithmetic operation is
/// often confusing so
/// parenthesis will always be added for a mix of these.
pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
/// Whether the operator is a shift operator `<<` or `>>`.
fn is_shift(op: &AssocOp) -> bool {
matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
}
/// Whether the operator is a arithmetic operator (`+`, `-`, `*`, `/`, `%`).
fn is_arith(op: &AssocOp) -> bool {
matches!(
*op,
AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
)
}
/// Whether the operator `op` needs parenthesis with the operator `other`
/// in the direction
/// `dir`.
fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
other.precedence() < op.precedence()
|| (other.precedence() == op.precedence()
&& ((op != other && associativity(op) != dir)
|| (op == other && associativity(op) != Associativity::Both)))
|| is_shift(op) && is_arith(other) || is_shift(other) && is_arith(op)
}
let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
needs_paren(&op, lop, Associativity::Left)
} else {
false
};
let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
needs_paren(&op, rop, Associativity::Right)
} else {
false
};
let lhs = ParenHelper::new(lhs_paren, lhs);
let rhs = ParenHelper::new(rhs_paren, rhs);
let sugg = match op {
AssocOp::Add |
AssocOp::BitAnd |
AssocOp::BitOr |
AssocOp::BitXor |
AssocOp::Divide |
AssocOp::Equal |
AssocOp::Greater |
AssocOp::GreaterEqual |
AssocOp::LAnd |
AssocOp::LOr |
AssocOp::Less |
AssocOp::LessEqual |
AssocOp::Modulus |
AssocOp::Multiply |
AssocOp::NotEqual |
AssocOp::ShiftLeft |
AssocOp::ShiftRight |
AssocOp::Subtract => format!("{} {} {}", lhs, op.to_ast_binop().expect("Those are AST ops").to_string(), rhs),
AssocOp::Assign => format!("{} = {}", lhs, rhs),
AssocOp::ObsoleteInPlace => format!("in ({}) {}", lhs, rhs),
AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_to_string(&token::BinOp(op)), rhs),
AssocOp::As => format!("{} as {}", lhs, rhs),
AssocOp::DotDot => format!("{}..{}", lhs, rhs),
AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
AssocOp::Colon => format!("{}: {}", lhs, rhs),
};
Sugg::BinOp(op, sugg.into())
}
/// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
}
#[derive(PartialEq, Eq, Clone, Copy)]
/// Operator associativity.
enum Associativity {
/// The operator is both left-associative and right-associative.
Both,
/// The operator is left-associative.
Left,
/// The operator is not associative.
None,
/// The operator is right-associative.
Right,
}
/// Return the associativity/fixity of an operator. The difference with
/// `AssocOp::fixity` is that
/// an operator can be both left and right associative (such as `+`:
/// `a + b + c == (a + b) + c == a + (b + c)`.
///
/// Chained `as` and explicit `:` type coercion never need inner parenthesis so
/// they are considered
/// associative.
fn associativity(op: &AssocOp) -> Associativity {
use syntax::util::parser::AssocOp::*;
match *op {
ObsoleteInPlace | Assign | AssignOp(_) => Associativity::Right,
Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
Divide |
Equal |
Greater |
GreaterEqual |
Less |
LessEqual |
Modulus |
NotEqual |
ShiftLeft |
ShiftRight |
Subtract => Associativity::Left,
DotDot | DotDotEq => Associativity::None,
}
}
/// Convert a `hir::BinOp` to the corresponding assigning binary operator.
fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
use syntax::parse::token::BinOpToken::*;
AssocOp::AssignOp(match op.node {
hir::BinOpKind::Add => Plus,
hir::BinOpKind::BitAnd => And,
hir::BinOpKind::BitOr => Or,
hir::BinOpKind::BitXor => Caret,
hir::BinOpKind::Div => Slash,
hir::BinOpKind::Mul => Star,
hir::BinOpKind::Rem => Percent,
hir::BinOpKind::Shl => Shl,
hir::BinOpKind::Shr => Shr,
hir::BinOpKind::Sub => Minus,
| hir::BinOpKind::And
| hir::BinOpKind::Eq
| hir::BinOpKind::Ge
| hir::BinOpKind::Gt
| hir::BinOpKind::Le
| hir::BinOpKind::Lt
| hir::BinOpKind::Ne
| hir::BinOpKind::Or
=> panic!("This operator does not exist"),
})
}
/// Convert an `ast::BinOp` to the corresponding assigning binary operator.
fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
use syntax::ast::BinOpKind::*;
use syntax::parse::token::BinOpToken;
AssocOp::AssignOp(match op.node {
Add => BinOpToken::Plus,
BitAnd => BinOpToken::And,
BitOr => BinOpToken::Or,
BitXor => BinOpToken::Caret,
Div => BinOpToken::Slash,
Mul => BinOpToken::Star,
Rem => BinOpToken::Percent,
Shl => BinOpToken::Shl,
Shr => BinOpToken::Shr,
Sub => BinOpToken::Minus,
And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
})
}
/// Return the indentation before `span` if there are nothing but `[ \t]`
/// before it on its line.
fn indentation<'a, T: LintContext<'a>>(cx: &T, span: Span) -> Option<String> {
let lo = cx.sess().source_map().lookup_char_pos(span.lo());
if let Some(line) = lo.file
.get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
{
if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
// we can mix char and byte positions here because we only consider `[ \t]`
if lo.col == CharPos(pos) {
Some(line[..pos].into())
} else {
None
}
} else {
None
}
} else {
None
}
}
/// Convenience extension trait for `DiagnosticBuilder`.
pub trait DiagnosticBuilderExt<'a, T: LintContext<'a>> {
/// Suggests to add an attribute to an item.
///
/// Correctly handles indentation of the attribute and item.
///
/// # Example
///
/// ```rust,ignore
/// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
/// ```
fn suggest_item_with_attr<D: Display + ?Sized>(&mut self, cx: &T, item: Span, msg: &str, attr: &D);
/// Suggest to add an item before another.
///
/// The item should not be indented (expect for inner indentation).
///
/// # Example
///
/// ```rust,ignore
/// db.suggest_prepend_item(cx, item,
/// "fn foo() {
/// bar();
/// }");
/// ```
fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str);
/// Suggest to completely remove an item.
///
/// This will remove an item and all following whitespace until the next non-whitespace
/// character. This should work correctly if item is on the same indentation level as the
/// following item.
///
/// # Example
///
/// ```rust,ignore
/// db.suggest_remove_item(cx, item, "remove this")
/// ```
fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str);
}
impl<'a, 'b, 'c, T: LintContext<'c>> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
fn suggest_item_with_attr<D: Display + ?Sized>(&mut self, cx: &T, item: Span, msg: &str, attr: &D) {
if let Some(indent) = indentation(cx, item) {
let span = item.with_hi(item.lo());
self.span_suggestion(span, msg, format!("{}\n{}", attr, indent));
}
}
fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str) {
if let Some(indent) = indentation(cx, item) {
let span = item.with_hi(item.lo());
let mut first = true;
let new_item = new_item
.lines()
.map(|l| {
if first {
first = false;
format!("{}\n", l)
} else {
format!("{}{}\n", indent, l)
}
})
.collect::<String>();
self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent));
}
}
fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str) {
let mut remove_span = item;
let hi = cx.sess().source_map().next_point(remove_span).hi();
let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
if let Some(ref src) = fmpos.fm.src {
let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
if let Some(non_whitespace_offset) = non_whitespace_offset {
remove_span = remove_span.with_hi(remove_span.hi() + BytePos(non_whitespace_offset as u32))
}
}
self.span_suggestion(remove_span, msg, String::new());
}
}