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Auto merge of #59058 - petrochenkov:assocrecov3, r=estebank
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 syntax: Better recovery for `$ty::AssocItem` and `ty!()::AssocItem`

This PR improves on #46788 covering a few missing cases.

Fixes #52307
Fixes #53776
r? @estebank
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@bors
bors committed Mar 23, 2019
2 parents f21dee2 + 1ab8ca3 commit d51a437
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Showing 7 changed files with 217 additions and 92 deletions.
170 changes: 82 additions & 88 deletions src/libsyntax/parse/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -118,23 +118,22 @@ enum BlockMode {
/// `token::Interpolated` tokens.
macro_rules! maybe_whole_expr {
($p:expr) => {
if let token::Interpolated(nt) = $p.token.clone() {
match *nt {
token::NtExpr(ref e) | token::NtLiteral(ref e) => {
if let token::Interpolated(nt) = &$p.token {
match &**nt {
token::NtExpr(e) | token::NtLiteral(e) => {
let e = e.clone();
$p.bump();
return Ok((*e).clone());
return Ok(e);
}
token::NtPath(ref path) => {
token::NtPath(path) => {
let path = path.clone();
$p.bump();
let span = $p.span;
let kind = ExprKind::Path(None, (*path).clone());
return Ok($p.mk_expr(span, kind, ThinVec::new()));
return Ok($p.mk_expr($p.span, ExprKind::Path(None, path), ThinVec::new()));
}
token::NtBlock(ref block) => {
token::NtBlock(block) => {
let block = block.clone();
$p.bump();
let span = $p.span;
let kind = ExprKind::Block((*block).clone(), None);
return Ok($p.mk_expr(span, kind, ThinVec::new()));
return Ok($p.mk_expr($p.span, ExprKind::Block(block, None), ThinVec::new()));
}
_ => {},
};
Expand All @@ -145,15 +144,31 @@ macro_rules! maybe_whole_expr {
/// As maybe_whole_expr, but for things other than expressions
macro_rules! maybe_whole {
($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
if let token::Interpolated(nt) = $p.token.clone() {
if let token::$constructor($x) = (*nt).clone() {
if let token::Interpolated(nt) = &$p.token {
if let token::$constructor(x) = &**nt {
let $x = x.clone();
$p.bump();
return Ok($e);
}
}
};
}

/// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
macro_rules! maybe_recover_from_interpolated_ty_qpath {
($self: expr, $allow_qpath_recovery: expr) => {
if $allow_qpath_recovery && $self.look_ahead(1, |t| t == &token::ModSep) {
if let token::Interpolated(nt) = &$self.token {
if let token::NtTy(ty) = &**nt {
let ty = ty.clone();
$self.bump();
return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_span, ty);
}
}
}
}
}

fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
if let Some(ref mut rhs) = rhs {
lhs.append(rhs);
Expand All @@ -172,48 +187,38 @@ enum PrevTokenKind {
Other,
}

trait RecoverQPath: Sized {
trait RecoverQPath: Sized + 'static {
const PATH_STYLE: PathStyle = PathStyle::Expr;
fn to_ty(&self) -> Option<P<Ty>>;
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self;
fn to_string(&self) -> String;
fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
}

impl RecoverQPath for Ty {
const PATH_STYLE: PathStyle = PathStyle::Type;
fn to_ty(&self) -> Option<P<Ty>> {
Some(P(self.clone()))
}
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: TyKind::Path(qself, path), id: self.id }
}
fn to_string(&self) -> String {
pprust::ty_to_string(self)
fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: TyKind::Path(qself, path), id: ast::DUMMY_NODE_ID }
}
}

impl RecoverQPath for Pat {
fn to_ty(&self) -> Option<P<Ty>> {
self.to_ty()
}
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: PatKind::Path(qself, path), id: self.id }
}
fn to_string(&self) -> String {
pprust::pat_to_string(self)
fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: PatKind::Path(qself, path), id: ast::DUMMY_NODE_ID }
}
}

impl RecoverQPath for Expr {
fn to_ty(&self) -> Option<P<Ty>> {
self.to_ty()
}
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: ExprKind::Path(qself, path),
id: self.id, attrs: self.attrs.clone() }
}
fn to_string(&self) -> String {
pprust::expr_to_string(self)
attrs: ThinVec::new(), id: ast::DUMMY_NODE_ID }
}
}

Expand Down Expand Up @@ -1649,6 +1654,7 @@ impl<'a> Parser<'a> {

fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
maybe_whole!(self, NtTy, |x| x);

let lo = self.span;
Expand Down Expand Up @@ -1800,14 +1806,12 @@ impl<'a> Parser<'a> {
};

let span = lo.to(self.prev_span);
let ty = Ty { node, span, id: ast::DUMMY_NODE_ID };
let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });

// Try to recover from use of `+` with incorrect priority.
self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
let ty = self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)?;

Ok(P(ty))
self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
}

fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
Expand Down Expand Up @@ -1878,36 +1882,40 @@ impl<'a> Parser<'a> {
Ok(())
}

// Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: T, allow_recovery: bool)
-> PResult<'a, T> {
/// Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
/// Attempt to convert the base expression/pattern/type into a type, parse the `::AssocItem`
/// tail, and combine them into a `<Ty>::AssocItem` expression/pattern/type.
fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: P<T>, allow_recovery: bool)
-> PResult<'a, P<T>> {
// Do not add `::` to expected tokens.
if !allow_recovery || self.token != token::ModSep {
return Ok(base);
if allow_recovery && self.token == token::ModSep {
if let Some(ty) = base.to_ty() {
return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
}
}
let ty = match base.to_ty() {
Some(ty) => ty,
None => return Ok(base),
};
Ok(base)
}

self.bump(); // `::`
let mut segments = Vec::new();
self.parse_path_segments(&mut segments, T::PATH_STYLE, true)?;
/// Given an already parsed `Ty` parse the `::AssocItem` tail and
/// combine them into a `<Ty>::AssocItem` expression/pattern/type.
fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(&mut self, ty_span: Span, ty: P<Ty>)
-> PResult<'a, P<T>> {
self.expect(&token::ModSep)?;

let span = ty.span.to(self.prev_span);
let path_span = span.to(span); // use an empty path since `position` == 0
let recovered = base.to_recovered(
Some(QSelf { ty, path_span, position: 0 }),
ast::Path { segments, span },
);
let mut path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
self.parse_path_segments(&mut path.segments, T::PATH_STYLE, true)?;
path.span = ty_span.to(self.prev_span);

let ty_str = self.sess.source_map().span_to_snippet(ty_span)
.unwrap_or_else(|_| pprust::ty_to_string(&ty));
self.diagnostic()
.struct_span_err(span, "missing angle brackets in associated item path")
.struct_span_err(path.span, "missing angle brackets in associated item path")
.span_suggestion( // this is a best-effort recovery
span, "try", recovered.to_string(), Applicability::MaybeIncorrect
path.span, "try", format!("<{}>::{}", ty_str, path), Applicability::MaybeIncorrect
).emit();

Ok(recovered)
let path_span = ty_span.shrink_to_hi(); // use an empty path since `position` == 0
Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
}

fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
Expand Down Expand Up @@ -2572,15 +2580,6 @@ impl<'a> Parser<'a> {
ExprKind::AssignOp(binop, lhs, rhs)
}

pub fn mk_mac_expr(&mut self, span: Span, m: Mac_, attrs: ThinVec<Attribute>) -> P<Expr> {
P(Expr {
id: ast::DUMMY_NODE_ID,
node: ExprKind::Mac(source_map::Spanned {node: m, span: span}),
span,
attrs,
})
}

fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
let delim = match self.token {
token::OpenDelim(delim) => delim,
Expand Down Expand Up @@ -2610,6 +2609,7 @@ impl<'a> Parser<'a> {
/// N.B., this does not parse outer attributes, and is private because it only works
/// correctly if called from `parse_dot_or_call_expr()`.
fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
maybe_recover_from_interpolated_ty_qpath!(self, true);
maybe_whole_expr!(self);

// Outer attributes are already parsed and will be
Expand Down Expand Up @@ -2824,29 +2824,23 @@ impl<'a> Parser<'a> {
db.note("variable declaration using `let` is a statement");
return Err(db);
} else if self.token.is_path_start() {
let pth = self.parse_path(PathStyle::Expr)?;
let path = self.parse_path(PathStyle::Expr)?;

// `!`, as an operator, is prefix, so we know this isn't that
if self.eat(&token::Not) {
// MACRO INVOCATION expression
let (delim, tts) = self.expect_delimited_token_tree()?;
let hi = self.prev_span;
let node = Mac_ { path: pth, tts, delim };
return Ok(self.mk_mac_expr(lo.to(hi), node, attrs))
}
if self.check(&token::OpenDelim(token::Brace)) {
hi = self.prev_span;
ex = ExprKind::Mac(respan(lo.to(hi), Mac_ { path, tts, delim }));
} else if self.check(&token::OpenDelim(token::Brace)) &&
!self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL) {
// This is a struct literal, unless we're prohibited
// from parsing struct literals here.
let prohibited = self.restrictions.contains(
Restrictions::NO_STRUCT_LITERAL
);
if !prohibited {
return self.parse_struct_expr(lo, pth, attrs);
}
return self.parse_struct_expr(lo, path, attrs);
} else {
hi = path.span;
ex = ExprKind::Path(None, path);
}

hi = pth.span;
ex = ExprKind::Path(None, pth);
} else {
if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
// Don't complain about bare semicolons after unclosed braces
Expand Down Expand Up @@ -2881,10 +2875,8 @@ impl<'a> Parser<'a> {
}
}

let expr = Expr { node: ex, span: lo.to(hi), id: ast::DUMMY_NODE_ID, attrs };
let expr = self.maybe_recover_from_bad_qpath(expr, true)?;

return Ok(P(expr));
let expr = self.mk_expr(lo.to(hi), ex, attrs);
self.maybe_recover_from_bad_qpath(expr, true)
}

fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
Expand Down Expand Up @@ -4584,6 +4576,7 @@ impl<'a> Parser<'a> {
allow_range_pat: bool,
expected: Option<&'static str>,
) -> PResult<'a, P<Pat>> {
maybe_recover_from_interpolated_ty_qpath!(self, true);
maybe_whole!(self, NtPat, |x| x);

let lo = self.span;
Expand Down Expand Up @@ -4759,7 +4752,7 @@ impl<'a> Parser<'a> {
}
}

let pat = Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID };
let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
let pat = self.maybe_recover_from_bad_qpath(pat, true)?;

if !allow_range_pat {
Expand All @@ -4785,7 +4778,7 @@ impl<'a> Parser<'a> {
}
}

Ok(P(pat))
Ok(pat)
}

/// Parses `ident` or `ident @ pat`.
Expand Down Expand Up @@ -5249,7 +5242,8 @@ impl<'a> Parser<'a> {
self.warn_missing_semicolon();
StmtKind::Mac(P((mac, style, attrs.into())))
} else {
let e = self.mk_mac_expr(lo.to(hi), mac.node, ThinVec::new());
let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
let e = self.maybe_recover_from_bad_qpath(e, true)?;
let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
StmtKind::Expr(e)
Expand Down
16 changes: 16 additions & 0 deletions src/test/ui/did_you_mean/bad-assoc-expr.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,3 +18,19 @@ fn main() {
10 + (u8)::clone(&0);
//~^ ERROR missing angle brackets in associated item path
}

macro_rules! expr {
($ty: ty) => ($ty::clone(&0))
//~^ ERROR missing angle brackets in associated item path
}
macro_rules! ty {
() => (u8)
}

fn check_macros() {
expr!(u8);
let _ = ty!()::clone(&0);
//~^ ERROR missing angle brackets in associated item path
ty!()::clone(&0);
//~^ ERROR missing angle brackets in associated item path
}
23 changes: 22 additions & 1 deletion src/test/ui/did_you_mean/bad-assoc-expr.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,5 +34,26 @@ error: missing angle brackets in associated item path
LL | 10 + (u8)::clone(&0);
| ^^^^^^^^^^^ help: try: `<(u8)>::clone`

error: aborting due to 6 previous errors
error: missing angle brackets in associated item path
--> $DIR/bad-assoc-expr.rs:32:13
|
LL | let _ = ty!()::clone(&0);
| ^^^^^^^^^^^^ help: try: `<ty!()>::clone`

error: missing angle brackets in associated item path
--> $DIR/bad-assoc-expr.rs:34:5
|
LL | ty!()::clone(&0);
| ^^^^^^^^^^^^ help: try: `<ty!()>::clone`

error: missing angle brackets in associated item path
--> $DIR/bad-assoc-expr.rs:23:19
|
LL | ($ty: ty) => ($ty::clone(&0))
| ^^^^^^^^^^ help: try: `<$ty>::clone`
...
LL | expr!(u8);
| ---------- in this macro invocation

error: aborting due to 9 previous errors

18 changes: 18 additions & 0 deletions src/test/ui/did_you_mean/bad-assoc-pat.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,3 +16,21 @@ fn main() {
//~| ERROR no associated item named `AssocItem` found for type `(u8,)` in the current scope
}
}

macro_rules! pat {
($ty: ty) => ($ty::AssocItem)
//~^ ERROR missing angle brackets in associated item path
//~| ERROR no associated item named `AssocItem` found for type `u8` in the current scope
}
macro_rules! ty {
() => (u8)
}

fn check_macros() {
match 0u8 {
pat!(u8) => {}
ty!()::AssocItem => {}
//~^ ERROR missing angle brackets in associated item path
//~| ERROR no associated item named `AssocItem` found for type `u8` in the current scope
}
}
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