diff --git a/src/librustc_parse/parser/diagnostics.rs b/src/librustc_parse/parser/diagnostics.rs
index 9abfbc698c5cf..ecbd183b6e929 100644
--- a/src/librustc_parse/parser/diagnostics.rs
+++ b/src/librustc_parse/parser/diagnostics.rs
@@ -4,6 +4,7 @@ use rustc_data_structures::fx::FxHashSet;
use rustc_error_codes::*;
use rustc_errors::{pluralize, struct_span_err};
use rustc_errors::{Applicability, DiagnosticBuilder, Handler, PResult};
+use rustc_span::source_map::Spanned;
use rustc_span::symbol::kw;
use rustc_span::{MultiSpan, Span, SpanSnippetError, DUMMY_SP};
use syntax::ast::{
@@ -500,6 +501,58 @@ impl<'a> Parser<'a> {
}
}
+ /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
+ /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
+ /// parenthesising the leftmost comparison.
+ fn attempt_chained_comparison_suggestion(
+ &mut self,
+ err: &mut DiagnosticBuilder<'_>,
+ inner_op: &Expr,
+ outer_op: &Spanned<AssocOp>,
+ ) {
+ if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
+ match (op.node, &outer_op.node) {
+ // `x < y < z` and friends.
+ (BinOpKind::Lt, AssocOp::Less) | (BinOpKind::Lt, AssocOp::LessEqual) |
+ (BinOpKind::Le, AssocOp::LessEqual) | (BinOpKind::Le, AssocOp::Less) |
+ // `x > y > z` and friends.
+ (BinOpKind::Gt, AssocOp::Greater) | (BinOpKind::Gt, AssocOp::GreaterEqual) |
+ (BinOpKind::Ge, AssocOp::GreaterEqual) | (BinOpKind::Ge, AssocOp::Greater) => {
+ let expr_to_str = |e: &Expr| {
+ self.span_to_snippet(e.span)
+ .unwrap_or_else(|_| pprust::expr_to_string(&e))
+ };
+ err.span_suggestion(
+ inner_op.span.to(outer_op.span),
+ "split the comparison into two...",
+ format!(
+ "{} {} {} && {} {}",
+ expr_to_str(&l1),
+ op.node.to_string(),
+ expr_to_str(&r1),
+ expr_to_str(&r1),
+ outer_op.node.to_ast_binop().unwrap().to_string(),
+ ),
+ Applicability::MaybeIncorrect,
+ );
+ err.span_suggestion(
+ inner_op.span.to(outer_op.span),
+ "...or parenthesize one of the comparisons",
+ format!(
+ "({} {} {}) {}",
+ expr_to_str(&l1),
+ op.node.to_string(),
+ expr_to_str(&r1),
+ outer_op.node.to_ast_binop().unwrap().to_string(),
+ ),
+ Applicability::MaybeIncorrect,
+ );
+ }
+ _ => {}
+ }
+ }
+ }
+
/// Produces an error if comparison operators are chained (RFC #558).
/// We only need to check the LHS, not the RHS, because all comparison ops have same
/// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
@@ -515,27 +568,31 @@ impl<'a> Parser<'a> {
/// / \
/// inner_op r2
/// / \
- /// l1 r1
+ /// l1 r1
pub(super) fn check_no_chained_comparison(
&mut self,
- lhs: &Expr,
- outer_op: &AssocOp,
+ inner_op: &Expr,
+ outer_op: &Spanned<AssocOp>,
) -> PResult<'a, Option<P<Expr>>> {
debug_assert!(
- outer_op.is_comparison(),
+ outer_op.node.is_comparison(),
"check_no_chained_comparison: {:?} is not comparison",
- outer_op,
+ outer_op.node,
);
let mk_err_expr =
|this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err, AttrVec::new())));
- match lhs.kind {
+ match inner_op.kind {
ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
// Respan to include both operators.
let op_span = op.span.to(self.prev_span);
- let mut err = self
- .struct_span_err(op_span, "chained comparison operators require parentheses");
+ let mut err =
+ self.struct_span_err(op_span, "comparison operators cannot be chained");
+
+ // If it looks like a genuine attempt to chain operators (as opposed to a
+ // misformatted turbofish, for instance), suggest a correct form.
+ self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
let suggest = |err: &mut DiagnosticBuilder<'_>| {
err.span_suggestion_verbose(
@@ -547,12 +604,12 @@ impl<'a> Parser<'a> {
};
if op.node == BinOpKind::Lt &&
- *outer_op == AssocOp::Less || // Include `<` to provide this recommendation
- *outer_op == AssocOp::Greater
+ outer_op.node == AssocOp::Less || // Include `<` to provide this recommendation
+ outer_op.node == AssocOp::Greater
// even in a case like the following:
{
// Foo<Bar<Baz<Qux, ()>>>
- if *outer_op == AssocOp::Less {
+ if outer_op.node == AssocOp::Less {
let snapshot = self.clone();
self.bump();
// So far we have parsed `foo<bar<`, consume the rest of the type args.
@@ -584,7 +641,7 @@ impl<'a> Parser<'a> {
// FIXME: actually check that the two expressions in the binop are
// paths and resynthesize new fn call expression instead of using
// `ExprKind::Err` placeholder.
- mk_err_expr(self, lhs.span.to(self.prev_span))
+ mk_err_expr(self, inner_op.span.to(self.prev_span))
}
Err(mut expr_err) => {
expr_err.cancel();
@@ -606,7 +663,7 @@ impl<'a> Parser<'a> {
// FIXME: actually check that the two expressions in the binop are
// paths and resynthesize new fn call expression instead of using
// `ExprKind::Err` placeholder.
- mk_err_expr(self, lhs.span.to(self.prev_span))
+ mk_err_expr(self, inner_op.span.to(self.prev_span))
}
}
} else {
diff --git a/src/librustc_parse/parser/expr.rs b/src/librustc_parse/parser/expr.rs
index 90f15375aec42..3c286d363c9db 100644
--- a/src/librustc_parse/parser/expr.rs
+++ b/src/librustc_parse/parser/expr.rs
@@ -5,7 +5,7 @@ use super::{SemiColonMode, SeqSep, TokenExpectType};
use crate::maybe_recover_from_interpolated_ty_qpath;
use rustc_errors::{Applicability, PResult};
-use rustc_span::source_map::{self, Span};
+use rustc_span::source_map::{self, Span, Spanned};
use rustc_span::symbol::{kw, sym, Symbol};
use std::mem;
use syntax::ast::{self, AttrStyle, AttrVec, CaptureBy, Field, Ident, Lit, DUMMY_NODE_ID};
@@ -181,17 +181,17 @@ impl<'a> Parser<'a> {
};
let cur_op_span = self.token.span;
- let restrictions = if op.is_assign_like() {
+ let restrictions = if op.node.is_assign_like() {
self.restrictions & Restrictions::NO_STRUCT_LITERAL
} else {
self.restrictions
};
- let prec = op.precedence();
+ let prec = op.node.precedence();
if prec < min_prec {
break;
}
// Check for deprecated `...` syntax
- if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
+ if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
self.err_dotdotdot_syntax(self.token.span);
}
@@ -200,11 +200,12 @@ impl<'a> Parser<'a> {
}
self.bump();
- if op.is_comparison() {
+ if op.node.is_comparison() {
if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
return Ok(expr);
}
}
+ let op = op.node;
// Special cases:
if op == AssocOp::As {
lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
@@ -298,7 +299,7 @@ impl<'a> Parser<'a> {
}
fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
- match (self.expr_is_complete(lhs), self.check_assoc_op()) {
+ match (self.expr_is_complete(lhs), self.check_assoc_op().map(|op| op.node)) {
// Semi-statement forms are odd:
// See https://github.com/rust-lang/rust/issues/29071
(true, None) => false,
@@ -343,19 +344,22 @@ impl<'a> Parser<'a> {
/// The method does not advance the current token.
///
/// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
- fn check_assoc_op(&self) -> Option<AssocOp> {
- match (AssocOp::from_token(&self.token), &self.token.kind) {
- (op @ Some(_), _) => op,
- (None, token::Ident(sym::and, false)) => {
- self.error_bad_logical_op("and", "&&", "conjunction");
- Some(AssocOp::LAnd)
- }
- (None, token::Ident(sym::or, false)) => {
- self.error_bad_logical_op("or", "||", "disjunction");
- Some(AssocOp::LOr)
- }
- _ => None,
- }
+ fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
+ Some(Spanned {
+ node: match (AssocOp::from_token(&self.token), &self.token.kind) {
+ (Some(op), _) => op,
+ (None, token::Ident(sym::and, false)) => {
+ self.error_bad_logical_op("and", "&&", "conjunction");
+ AssocOp::LAnd
+ }
+ (None, token::Ident(sym::or, false)) => {
+ self.error_bad_logical_op("or", "||", "disjunction");
+ AssocOp::LOr
+ }
+ _ => return None,
+ },
+ span: self.token.span,
+ })
}
/// Error on `and` and `or` suggesting `&&` and `||` respectively.
diff --git a/src/test/ui/did_you_mean/issue-40396.rs b/src/test/ui/did_you_mean/issue-40396.rs
index 1893355205433..e4e94bb949237 100644
--- a/src/test/ui/did_you_mean/issue-40396.rs
+++ b/src/test/ui/did_you_mean/issue-40396.rs
@@ -1,8 +1,8 @@
fn main() {
(0..13).collect<Vec<i32>>();
- //~^ ERROR chained comparison
+ //~^ ERROR comparison operators cannot be chained
Vec<i32>::new();
- //~^ ERROR chained comparison
+ //~^ ERROR comparison operators cannot be chained
(0..13).collect<Vec<i32>();
- //~^ ERROR chained comparison
+ //~^ ERROR comparison operators cannot be chained
}
diff --git a/src/test/ui/did_you_mean/issue-40396.stderr b/src/test/ui/did_you_mean/issue-40396.stderr
index 749d1093ccab8..f952136a7bfe3 100644
--- a/src/test/ui/did_you_mean/issue-40396.stderr
+++ b/src/test/ui/did_you_mean/issue-40396.stderr
@@ -1,15 +1,23 @@
-error: chained comparison operators require parentheses
+error: comparison operators cannot be chained
--> $DIR/issue-40396.rs:2:20
|
LL | (0..13).collect<Vec<i32>>();
| ^^^^^
|
+help: split the comparison into two...
+ |
+LL | (0..13).collect < Vec && Vec <i32>>();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | ((0..13).collect < Vec) <i32>>();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^
help: use `::<...>` instead of `<...>` to specify type arguments
|
LL | (0..13).collect::<Vec<i32>>();
| ^^
-error: chained comparison operators require parentheses
+error: comparison operators cannot be chained
--> $DIR/issue-40396.rs:4:8
|
LL | Vec<i32>::new();
@@ -20,12 +28,20 @@ help: use `::<...>` instead of `<...>` to specify type arguments
LL | Vec::<i32>::new();
| ^^
-error: chained comparison operators require parentheses
+error: comparison operators cannot be chained
--> $DIR/issue-40396.rs:6:20
|
LL | (0..13).collect<Vec<i32>();
| ^^^^^
|
+help: split the comparison into two...
+ |
+LL | (0..13).collect < Vec && Vec <i32>();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | ((0..13).collect < Vec) <i32>();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^
help: use `::<...>` instead of `<...>` to specify type arguments
|
LL | (0..13).collect::<Vec<i32>();
diff --git a/src/test/ui/parser/chained-comparison-suggestion.rs b/src/test/ui/parser/chained-comparison-suggestion.rs
new file mode 100644
index 0000000000000..0431196f1744e
--- /dev/null
+++ b/src/test/ui/parser/chained-comparison-suggestion.rs
@@ -0,0 +1,40 @@
+// Check that we get nice suggestions when attempting a chained comparison.
+
+fn comp1() {
+ 1 < 2 <= 3; //~ ERROR comparison operators cannot be chained
+ //~^ ERROR mismatched types
+}
+
+fn comp2() {
+ 1 < 2 < 3; //~ ERROR comparison operators cannot be chained
+}
+
+fn comp3() {
+ 1 <= 2 < 3; //~ ERROR comparison operators cannot be chained
+ //~^ ERROR mismatched types
+}
+
+fn comp4() {
+ 1 <= 2 <= 3; //~ ERROR comparison operators cannot be chained
+ //~^ ERROR mismatched types
+}
+
+fn comp5() {
+ 1 > 2 >= 3; //~ ERROR comparison operators cannot be chained
+ //~^ ERROR mismatched types
+}
+
+fn comp6() {
+ 1 > 2 > 3; //~ ERROR comparison operators cannot be chained
+}
+
+fn comp7() {
+ 1 >= 2 > 3; //~ ERROR comparison operators cannot be chained
+}
+
+fn comp8() {
+ 1 >= 2 >= 3; //~ ERROR comparison operators cannot be chained
+ //~^ ERROR mismatched types
+}
+
+fn main() {}
diff --git a/src/test/ui/parser/chained-comparison-suggestion.stderr b/src/test/ui/parser/chained-comparison-suggestion.stderr
new file mode 100644
index 0000000000000..5c10a4599dd03
--- /dev/null
+++ b/src/test/ui/parser/chained-comparison-suggestion.stderr
@@ -0,0 +1,159 @@
+error: comparison operators cannot be chained
+ --> $DIR/chained-comparison-suggestion.rs:4:7
+ |
+LL | 1 < 2 <= 3;
+ | ^^^^^^
+ |
+help: split the comparison into two...
+ |
+LL | 1 < 2 && 2 <= 3;
+ | ^^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | (1 < 2) <= 3;
+ | ^^^^^^^^^^
+
+error: comparison operators cannot be chained
+ --> $DIR/chained-comparison-suggestion.rs:9:7
+ |
+LL | 1 < 2 < 3;
+ | ^^^^^
+ |
+ = help: use `::<...>` instead of `<...>` to specify type arguments
+ = help: or use `(...)` if you meant to specify fn arguments
+help: split the comparison into two...
+ |
+LL | 1 < 2 && 2 < 3;
+ | ^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | (1 < 2) < 3;
+ | ^^^^^^^^^
+
+error: comparison operators cannot be chained
+ --> $DIR/chained-comparison-suggestion.rs:13:7
+ |
+LL | 1 <= 2 < 3;
+ | ^^^^^^
+ |
+help: split the comparison into two...
+ |
+LL | 1 <= 2 && 2 < 3;
+ | ^^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | (1 <= 2) < 3;
+ | ^^^^^^^^^^
+
+error: comparison operators cannot be chained
+ --> $DIR/chained-comparison-suggestion.rs:18:7
+ |
+LL | 1 <= 2 <= 3;
+ | ^^^^^^^
+ |
+help: split the comparison into two...
+ |
+LL | 1 <= 2 && 2 <= 3;
+ | ^^^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | (1 <= 2) <= 3;
+ | ^^^^^^^^^^^
+
+error: comparison operators cannot be chained
+ --> $DIR/chained-comparison-suggestion.rs:23:7
+ |
+LL | 1 > 2 >= 3;
+ | ^^^^^^
+ |
+help: split the comparison into two...
+ |
+LL | 1 > 2 && 2 >= 3;
+ | ^^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | (1 > 2) >= 3;
+ | ^^^^^^^^^^
+
+error: comparison operators cannot be chained
+ --> $DIR/chained-comparison-suggestion.rs:28:7
+ |
+LL | 1 > 2 > 3;
+ | ^^^^^
+ |
+ = help: use `::<...>` instead of `<...>` to specify type arguments
+ = help: or use `(...)` if you meant to specify fn arguments
+help: split the comparison into two...
+ |
+LL | 1 > 2 && 2 > 3;
+ | ^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | (1 > 2) > 3;
+ | ^^^^^^^^^
+
+error: comparison operators cannot be chained
+ --> $DIR/chained-comparison-suggestion.rs:32:7
+ |
+LL | 1 >= 2 > 3;
+ | ^^^^^^
+ |
+ = help: use `::<...>` instead of `<...>` to specify type arguments
+ = help: or use `(...)` if you meant to specify fn arguments
+help: split the comparison into two...
+ |
+LL | 1 >= 2 && 2 > 3;
+ | ^^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | (1 >= 2) > 3;
+ | ^^^^^^^^^^
+
+error: comparison operators cannot be chained
+ --> $DIR/chained-comparison-suggestion.rs:36:7
+ |
+LL | 1 >= 2 >= 3;
+ | ^^^^^^^
+ |
+help: split the comparison into two...
+ |
+LL | 1 >= 2 && 2 >= 3;
+ | ^^^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | (1 >= 2) >= 3;
+ | ^^^^^^^^^^^
+
+error[E0308]: mismatched types
+ --> $DIR/chained-comparison-suggestion.rs:4:14
+ |
+LL | 1 < 2 <= 3;
+ | ^ expected `bool`, found integer
+
+error[E0308]: mismatched types
+ --> $DIR/chained-comparison-suggestion.rs:13:14
+ |
+LL | 1 <= 2 < 3;
+ | ^ expected `bool`, found integer
+
+error[E0308]: mismatched types
+ --> $DIR/chained-comparison-suggestion.rs:18:15
+ |
+LL | 1 <= 2 <= 3;
+ | ^ expected `bool`, found integer
+
+error[E0308]: mismatched types
+ --> $DIR/chained-comparison-suggestion.rs:23:14
+ |
+LL | 1 > 2 >= 3;
+ | ^ expected `bool`, found integer
+
+error[E0308]: mismatched types
+ --> $DIR/chained-comparison-suggestion.rs:36:15
+ |
+LL | 1 >= 2 >= 3;
+ | ^ expected `bool`, found integer
+
+error: aborting due to 13 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/parser/require-parens-for-chained-comparison.rs b/src/test/ui/parser/require-parens-for-chained-comparison.rs
index 9c7a25d589a1f..e27b03dddc5be 100644
--- a/src/test/ui/parser/require-parens-for-chained-comparison.rs
+++ b/src/test/ui/parser/require-parens-for-chained-comparison.rs
@@ -3,24 +3,26 @@ struct X;
fn main() {
false == false == false;
- //~^ ERROR chained comparison operators require parentheses
+ //~^ ERROR comparison operators cannot be chained
false == 0 < 2;
- //~^ ERROR chained comparison operators require parentheses
+ //~^ ERROR comparison operators cannot be chained
//~| ERROR mismatched types
//~| ERROR mismatched types
f<X>();
- //~^ ERROR chained comparison operators require parentheses
+ //~^ ERROR comparison operators cannot be chained
//~| HELP use `::<...>` instead of `<...>` to specify type arguments
f<Result<Option<X>, Option<Option<X>>>(1, 2);
- //~^ ERROR chained comparison operators require parentheses
+ //~^ ERROR comparison operators cannot be chained
+ //~| HELP split the comparison into two...
+ //~| ...or parenthesize one of the comparisons
//~| HELP use `::<...>` instead of `<...>` to specify type arguments
use std::convert::identity;
let _ = identity<u8>;
- //~^ ERROR chained comparison operators require parentheses
+ //~^ ERROR comparison operators cannot be chained
//~| HELP use `::<...>` instead of `<...>` to specify type arguments
//~| HELP or use `(...)` if you meant to specify fn arguments
}
diff --git a/src/test/ui/parser/require-parens-for-chained-comparison.stderr b/src/test/ui/parser/require-parens-for-chained-comparison.stderr
index bece9a388008c..44edf2de7f8de 100644
--- a/src/test/ui/parser/require-parens-for-chained-comparison.stderr
+++ b/src/test/ui/parser/require-parens-for-chained-comparison.stderr
@@ -1,16 +1,16 @@
-error: chained comparison operators require parentheses
+error: comparison operators cannot be chained
--> $DIR/require-parens-for-chained-comparison.rs:5:11
|
LL | false == false == false;
| ^^^^^^^^^^^
-error: chained comparison operators require parentheses
+error: comparison operators cannot be chained
--> $DIR/require-parens-for-chained-comparison.rs:8:11
|
LL | false == 0 < 2;
| ^^^^^^
-error: chained comparison operators require parentheses
+error: comparison operators cannot be chained
--> $DIR/require-parens-for-chained-comparison.rs:13:6
|
LL | f<X>();
@@ -21,19 +21,27 @@ help: use `::<...>` instead of `<...>` to specify type arguments
LL | f::<X>();
| ^^
-error: chained comparison operators require parentheses
+error: comparison operators cannot be chained
--> $DIR/require-parens-for-chained-comparison.rs:17:6
|
LL | f<Result<Option<X>, Option<Option<X>>>(1, 2);
| ^^^^^^^^
|
+help: split the comparison into two...
+ |
+LL | f < Result && Result <Option<X>, Option<Option<X>>>(1, 2);
+ | ^^^^^^^^^^^^^^^^^^^^^^
+help: ...or parenthesize one of the comparisons
+ |
+LL | (f < Result) <Option<X>, Option<Option<X>>>(1, 2);
+ | ^^^^^^^^^^^^^^
help: use `::<...>` instead of `<...>` to specify type arguments
|
LL | f::<Result<Option<X>, Option<Option<X>>>(1, 2);
| ^^
-error: chained comparison operators require parentheses
- --> $DIR/require-parens-for-chained-comparison.rs:22:21
+error: comparison operators cannot be chained
+ --> $DIR/require-parens-for-chained-comparison.rs:24:21
|
LL | let _ = identity<u8>;
| ^^^^