From 60560bc2a2c149e179cd7e58a8b48e06c2c4e3f4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sat, 21 Sep 2019 17:11:09 -0700
Subject: [PATCH 1/2] Parse assoc type bounds in generic params and provide
custom diagnostic
---
src/libsyntax/parse/parser/generics.rs | 99 ++++++++++++-------
src/test/ui/parser/assoc-type-in-type-arg.rs | 11 +++
.../ui/parser/assoc-type-in-type-arg.stderr | 8 ++
3 files changed, 80 insertions(+), 38 deletions(-)
create mode 100644 src/test/ui/parser/assoc-type-in-type-arg.rs
create mode 100644 src/test/ui/parser/assoc-type-in-type-arg.stderr
diff --git a/src/libsyntax/parse/parser/generics.rs b/src/libsyntax/parse/parser/generics.rs
index 3e6118ad86f47..1ffdda19c80b5 100644
--- a/src/libsyntax/parse/parser/generics.rs
+++ b/src/libsyntax/parse/parser/generics.rs
@@ -100,13 +100,31 @@ impl<'a> Parser<'a> {
} else if self.check_ident() {
// Parse type parameter.
params.push(self.parse_ty_param(attrs)?);
+ } else if self.token.can_begin_type() {
+ // Trying to write an associated type bound? (#26271)
+ let snapshot = self.clone();
+ match self.parse_ty_where_predicate() {
+ Ok(where_predicate) => {
+ self.struct_span_err(
+ where_predicate.span(),
+ "associated type bounds do not belong here",
+ )
+ .span_label(where_predicate.span(), "belongs in `where` clause")
+ .emit();
+ }
+ Err(mut err) => {
+ err.cancel();
+ std::mem::replace(self, snapshot);
+ break
+ }
+ }
} else {
// Check for trailing attributes and stop parsing.
if !attrs.is_empty() {
if !params.is_empty() {
self.struct_span_err(
attrs[0].span,
- &format!("trailing attribute after generic parameter"),
+ "trailing attribute after generic parameter",
)
.span_label(attrs[0].span, "attributes must go before parameters")
.emit();
@@ -202,43 +220,7 @@ impl<'a> Parser<'a> {
}
));
} else if self.check_type() {
- // Parse optional `for<'a, 'b>`.
- // This `for` is parsed greedily and applies to the whole predicate,
- // the bounded type can have its own `for` applying only to it.
- // Examples:
- // * `for<'a> Trait1<'a>: Trait2<'a /* ok */>`
- // * `(for<'a> Trait1<'a>): Trait2<'a /* not ok */>`
- // * `for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /* ok */, 'b /* not ok */>`
- let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
-
- // Parse type with mandatory colon and (possibly empty) bounds,
- // or with mandatory equality sign and the second type.
- let ty = self.parse_ty()?;
- if self.eat(&token::Colon) {
- let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
- where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
- ast::WhereBoundPredicate {
- span: lo.to(self.prev_span),
- bound_generic_params: lifetime_defs,
- bounded_ty: ty,
- bounds,
- }
- ));
- // FIXME: Decide what should be used here, `=` or `==`.
- // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
- } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
- let rhs_ty = self.parse_ty()?;
- where_clause.predicates.push(ast::WherePredicate::EqPredicate(
- ast::WhereEqPredicate {
- span: lo.to(self.prev_span),
- lhs_ty: ty,
- rhs_ty,
- id: ast::DUMMY_NODE_ID,
- }
- ));
- } else {
- return self.unexpected();
- }
+ where_clause.predicates.push(self.parse_ty_where_predicate()?);
} else {
break
}
@@ -252,6 +234,47 @@ impl<'a> Parser<'a> {
Ok(where_clause)
}
+ fn parse_ty_where_predicate(&mut self) -> PResult<'a, ast::WherePredicate> {
+ let lo = self.token.span;
+ // Parse optional `for<'a, 'b>`.
+ // This `for` is parsed greedily and applies to the whole predicate,
+ // the bounded type can have its own `for` applying only to it.
+ // Examples:
+ // * `for<'a> Trait1<'a>: Trait2<'a /* ok */>`
+ // * `(for<'a> Trait1<'a>): Trait2<'a /* not ok */>`
+ // * `for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /* ok */, 'b /* not ok */>`
+ let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
+
+ // Parse type with mandatory colon and (possibly empty) bounds,
+ // or with mandatory equality sign and the second type.
+ let ty = self.parse_ty()?;
+ if self.eat(&token::Colon) {
+ let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
+ Ok(ast::WherePredicate::BoundPredicate(
+ ast::WhereBoundPredicate {
+ span: lo.to(self.prev_span),
+ bound_generic_params: lifetime_defs,
+ bounded_ty: ty,
+ bounds,
+ }
+ ))
+ // FIXME: Decide what should be used here, `=` or `==`.
+ // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
+ } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
+ let rhs_ty = self.parse_ty()?;
+ Ok(ast::WherePredicate::EqPredicate(
+ ast::WhereEqPredicate {
+ span: lo.to(self.prev_span),
+ lhs_ty: ty,
+ rhs_ty,
+ id: ast::DUMMY_NODE_ID,
+ }
+ ))
+ } else {
+ self.unexpected()
+ }
+ }
+
pub(super) fn choose_generics_over_qpath(&self) -> bool {
// There's an ambiguity between generic parameters and qualified paths in impls.
// If we see `<` it may start both, so we have to inspect some following tokens.
diff --git a/src/test/ui/parser/assoc-type-in-type-arg.rs b/src/test/ui/parser/assoc-type-in-type-arg.rs
new file mode 100644
index 0000000000000..09765f01371aa
--- /dev/null
+++ b/src/test/ui/parser/assoc-type-in-type-arg.rs
@@ -0,0 +1,11 @@
+trait Tr {
+ type TrSubtype;
+}
+
+struct Bar<'a, Item: Tr, <Item as Tr>::TrSubtype: 'a> {
+ //~^ ERROR associated type bounds do not belong here
+ item: Item,
+ item_sub: &'a <Item as Tr>::TrSubtype,
+}
+
+fn main() {}
diff --git a/src/test/ui/parser/assoc-type-in-type-arg.stderr b/src/test/ui/parser/assoc-type-in-type-arg.stderr
new file mode 100644
index 0000000000000..06addb0241725
--- /dev/null
+++ b/src/test/ui/parser/assoc-type-in-type-arg.stderr
@@ -0,0 +1,8 @@
+error: associated type bounds do not belong here
+ --> $DIR/assoc-type-in-type-arg.rs:5:26
+ |
+LL | struct Bar<'a, Item: Tr, <Item as Tr>::TrSubtype: 'a> {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ belongs in `where` clause
+
+error: aborting due to previous error
+
From 0f2f16db5364663b4a2f092bba61dc3b056902e3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sat, 21 Sep 2019 18:57:37 -0700
Subject: [PATCH 2/2] review comments: wording
---
src/libsyntax/parse/parser/generics.rs | 2 +-
src/test/ui/parser/assoc-type-in-type-arg.rs | 2 +-
src/test/ui/parser/assoc-type-in-type-arg.stderr | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/libsyntax/parse/parser/generics.rs b/src/libsyntax/parse/parser/generics.rs
index 1ffdda19c80b5..2ecd9cca3c64b 100644
--- a/src/libsyntax/parse/parser/generics.rs
+++ b/src/libsyntax/parse/parser/generics.rs
@@ -107,7 +107,7 @@ impl<'a> Parser<'a> {
Ok(where_predicate) => {
self.struct_span_err(
where_predicate.span(),
- "associated type bounds do not belong here",
+ "bounds on associated types do not belong here",
)
.span_label(where_predicate.span(), "belongs in `where` clause")
.emit();
diff --git a/src/test/ui/parser/assoc-type-in-type-arg.rs b/src/test/ui/parser/assoc-type-in-type-arg.rs
index 09765f01371aa..000956ea24fad 100644
--- a/src/test/ui/parser/assoc-type-in-type-arg.rs
+++ b/src/test/ui/parser/assoc-type-in-type-arg.rs
@@ -3,7 +3,7 @@ trait Tr {
}
struct Bar<'a, Item: Tr, <Item as Tr>::TrSubtype: 'a> {
- //~^ ERROR associated type bounds do not belong here
+ //~^ ERROR bounds on associated types do not belong here
item: Item,
item_sub: &'a <Item as Tr>::TrSubtype,
}
diff --git a/src/test/ui/parser/assoc-type-in-type-arg.stderr b/src/test/ui/parser/assoc-type-in-type-arg.stderr
index 06addb0241725..b637702f21e90 100644
--- a/src/test/ui/parser/assoc-type-in-type-arg.stderr
+++ b/src/test/ui/parser/assoc-type-in-type-arg.stderr
@@ -1,4 +1,4 @@
-error: associated type bounds do not belong here
+error: bounds on associated types do not belong here
--> $DIR/assoc-type-in-type-arg.rs:5:26
|
LL | struct Bar<'a, Item: Tr, <Item as Tr>::TrSubtype: 'a> {