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syntax: Apply recovery for casts to type ascription
Fix spans, add some comments
This commit is contained in:
Vadim Petrochenkov
parent
5fa1c1b5f3
commit
4323877e92
@ -1081,6 +1081,16 @@ impl<'a> Parser<'a> {
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None => token::CloseDelim(self.token_cursor.frame.delim),
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})
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}
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fn look_ahead_span(&self, dist: usize) -> Span {
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if dist == 0 {
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return self.span
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}
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match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
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Some(TokenTree::Token(span, _)) | Some(TokenTree::Delimited(span, _)) => span,
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None => self.look_ahead_span(dist - 1),
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}
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}
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pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
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self.sess.span_diagnostic.struct_span_fatal(self.span, m)
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}
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@ -2805,13 +2815,10 @@ impl<'a> Parser<'a> {
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}
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// Special cases:
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if op == AssocOp::As {
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// Save the state of the parser before parsing type normally, in case there is a
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// LessThan comparison after this cast.
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lhs = self.parse_assoc_op_as(lhs, lhs_span)?;
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lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
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continue
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} else if op == AssocOp::Colon {
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let rhs = self.parse_ty_no_plus()?;
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lhs = self.mk_expr(lhs_span.to(rhs.span), ExprKind::Type(lhs, rhs), ThinVec::new());
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lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
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continue
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} else if op == AssocOp::DotDot || op == AssocOp::DotDotDot {
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// If we didn’t have to handle `x..`/`x...`, it would be pretty easy to
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@ -2905,61 +2912,61 @@ impl<'a> Parser<'a> {
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Ok(lhs)
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}
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fn parse_assoc_op_as(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
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let rp = self.clone();
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fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
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expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
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-> PResult<'a, P<Expr>> {
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let mk_expr = |this: &mut Self, rhs: P<Ty>| {
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this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
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};
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// Save the state of the parser before parsing type normally, in case there is a
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// LessThan comparison after this cast.
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let parser_snapshot_before_type = self.clone();
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match self.parse_ty_no_plus() {
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Ok(rhs) => {
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Ok(self.mk_expr(lhs_span.to(rhs.span),
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ExprKind::Cast(lhs, rhs),
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ThinVec::new()))
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Ok(mk_expr(self, rhs))
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}
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Err(mut err) => {
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let rp_err = self.clone();
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let sp = rp_err.span.clone();
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Err(mut type_err) => {
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// Rewind to before attempting to parse the type with generics, to recover
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// from situations like `x as usize < y` in which we first tried to parse
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// `usize < y` as a type with generic arguments.
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let parser_snapshot_after_type = self.clone();
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mem::replace(self, parser_snapshot_before_type);
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// Rewind to before attempting to parse the type with generics, to get
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// arround #22644.
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mem::replace(self, rp);
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let lo = self.span;
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match self.parse_path_without_generics(PathStyle::Type) {
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Ok(path) => {
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// Successfully parsed the type leaving a `<` yet to parse
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err.cancel();
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let codemap = self.sess.codemap();
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let suggestion_span = lhs_span.to(self.prev_span);
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let warn_message = match codemap.span_to_snippet(self.prev_span) {
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Ok(lstring) => format!("`{}`", lstring),
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_ => "a type".to_string(),
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};
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// Successfully parsed the type path leaving a `<` yet to parse.
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type_err.cancel();
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// Report non-fatal diagnostics, keep `x as usize` as an expression
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// in AST and continue parsing.
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let msg = format!("`<` is interpreted as a start of generic \
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arguments for {}, not a comparison",
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warn_message);
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let mut err = self.sess.span_diagnostic.struct_span_err(sp, &msg);
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err.span_label(sp, "interpreted as generic argument");
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arguments for `{}`, not a comparison", path);
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let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
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err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
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"interpreted as generic arguments");
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err.span_label(self.span, "not interpreted as comparison");
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let suggestion = match codemap.span_to_snippet(suggestion_span) {
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Ok(lstring) => format!("({})", lstring),
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_ => format!("(<expression> as <type>)")
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};
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err.span_suggestion(suggestion_span,
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let expr = mk_expr(self, P(Ty {
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span: path.span,
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node: TyKind::Path(None, path),
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id: ast::DUMMY_NODE_ID
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}));
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let expr_str = self.sess.codemap().span_to_snippet(expr.span)
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.unwrap_or(pprust::expr_to_string(&expr));
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err.span_suggestion(expr.span,
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"if you want to compare the casted value then write:",
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suggestion);
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format!("({})", expr_str));
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err.emit();
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let path = TyKind::Path(None, path);
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let span = lo.to(self.prev_span);
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let rhs = P(Ty { node: path, span: span, id: ast::DUMMY_NODE_ID });
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// Letting the parser accept the recovered type to avoid further errors,
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// but the code will still not compile due to the error emitted above.
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Ok(self.mk_expr(lhs_span.to(rhs.span),
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ExprKind::Cast(lhs, rhs),
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ThinVec::new()))
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Ok(expr)
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}
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Err(mut path_err) => {
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// Still couldn't parse, return original error and parser state
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// Couldn't parse as a path, return original error and parser state.
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path_err.cancel();
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mem::replace(self, rp_err);
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Err(err)
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mem::replace(self, parser_snapshot_after_type);
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Err(type_err)
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}
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}
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}
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@ -10,10 +10,16 @@
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fn main() {
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let a : u32 = 0;
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let b : usize = 0;
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let long_name : usize = 0;
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println!("{}", a as usize > long_name);
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println!("{}", a as usize < long_name);
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println!("{}{}", a as usize < long_name, long_name);
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println!("{}", a as usize < 4);
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println!("{}", a: usize > long_name);
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println!("{}{}", a: usize < long_name, long_name);
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println!("{}", a: usize < 4);
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println!("{}", a as usize > b);
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println!("{}", a as usize < b);
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println!("{}", a
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as
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usize
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@ -28,4 +34,6 @@ fn main() {
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usize
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<
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5);
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println!("{}", a: &mut 4);
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}
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@ -1,48 +1,104 @@
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error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
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--> $DIR/issue-22644.rs:16:33
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--> $DIR/issue-22644.rs:16:31
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16 | println!("{}", a as usize < b);
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| - ^ interpreted as generic argument
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16 | println!("{}", a as usize < long_name);
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| ^ --------- interpreted as generic arguments
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| |
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| not interpreted as comparison
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help: if you want to compare the casted value then write:
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16 | println!("{}", (a as usize) < b);
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16 | println!("{}", (a as usize) < long_name);
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| ^^^^^^^^^^^^
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error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
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--> $DIR/issue-22644.rs:21:20
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--> $DIR/issue-22644.rs:17:33
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20 | <
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| - not interpreted as comparison
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21 | 4);
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| ^ interpreted as generic argument
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17 | println!("{}{}", a as usize < long_name, long_name);
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| ^ -------------------- interpreted as generic arguments
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| |
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| not interpreted as comparison
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help: if you want to compare the casted value then write:
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17 | println!("{}", (a
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18 | as
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19 | usize)
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17 | println!("{}{}", (a as usize) < long_name, long_name);
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| ^^^^^^^^^^^^
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error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
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--> $DIR/issue-22644.rs:18:31
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18 | println!("{}", a as usize < 4);
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| ^ - interpreted as generic arguments
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| |
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| not interpreted as comparison
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help: if you want to compare the casted value then write:
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18 | println!("{}", (a as usize) < 4);
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| ^^^^^^^^^^^^
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error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
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--> $DIR/issue-22644.rs:20:31
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20 | println!("{}{}", a: usize < long_name, long_name);
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| ^ -------------------- interpreted as generic arguments
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| |
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| not interpreted as comparison
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help: if you want to compare the casted value then write:
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20 | println!("{}{}", (a: usize) < long_name, long_name);
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| ^^^^^^^^^^
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error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
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--> $DIR/issue-22644.rs:21:29
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21 | println!("{}", a: usize < 4);
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| ^ - interpreted as generic arguments
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| |
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| not interpreted as comparison
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help: if you want to compare the casted value then write:
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21 | println!("{}", (a: usize) < 4);
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| ^^^^^^^^^^
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error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
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--> $DIR/issue-22644.rs:26:20
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26 | <
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| ^ not interpreted as comparison
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27 | 4);
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| - interpreted as generic arguments
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help: if you want to compare the casted value then write:
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23 | println!("{}", (a
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24 | as
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25 | usize)
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error: `<` is interpreted as a start of generic arguments for `usize`, not a comparison
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--> $DIR/issue-22644.rs:30:20
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--> $DIR/issue-22644.rs:35:20
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29 | <
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| - not interpreted as comparison
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30 | 5);
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| ^ interpreted as generic argument
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35 | <
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| ^ not interpreted as comparison
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36 | 5);
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| - interpreted as generic arguments
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help: if you want to compare the casted value then write:
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22 | println!("{}", (a
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23 |
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24 |
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25 | as
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26 |
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27 |
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28 | println!("{}", (a
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29 |
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30 |
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31 | as
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32 |
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33 |
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...
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error: aborting due to 3 previous errors
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error: expected type, found `4`
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--> $DIR/issue-22644.rs:38:28
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38 | println!("{}", a: &mut 4);
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| ^
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@ -2,12 +2,17 @@ error: `<` is interpreted as a start of generic arguments for `u32`, not a compa
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--> $DIR/issue-42954.rs:13:19
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13 | $i as u32 < 0
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| - ^ interpreted as generic argument
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| ^ - interpreted as generic arguments
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| |
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| not interpreted as comparison
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...
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19 | is_plainly_printable!(c);
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| ------------------------- in this macro invocation
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help: if you want to compare the casted value then write:
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| ($i as u32) < 0
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13 | ($i as u32) < 0
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| ^^^^^^^^^^^
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error: aborting due to previous error
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