syntax: do not panic if find enum or struct but find ident

Closes #22426
Closes #22589
Closes #22665
Closes #22712

src/libsyntax/parse/parser.rs

@@ -3505,52 +3505,44 @@ impl<'a> Parser<'a> {
  self.bump();
  pat = PatStruct(enum_path, fields, etc);
  }
- _ => {
- let mut args: Vec<P<Pat>> = Vec::new();
- match self.token {
- token::OpenDelim(token::Paren) => {
- let is_dotdot = self.look_ahead(1, |t| {
- match *t {
- token::DotDot => true,
- _ => false,
- }
- });
- if is_dotdot {
- // This is a "top constructor only" pat
- self.bump();
- self.bump();
- self.expect(&token::CloseDelim(token::Paren));
- pat = PatEnum(enum_path, None);
- } else {
- args = self.parse_enum_variant_seq(
- &token::OpenDelim(token::Paren),
- &token::CloseDelim(token::Paren),
- seq_sep_trailing_allowed(token::Comma),
- |p| p.parse_pat()
- );
- pat = PatEnum(enum_path, Some(args));
+ token::OpenDelim(token::Paren) => {
+ let is_dotdot = self.look_ahead(1, |t| {
+ match *t {
+ token::DotDot => true,
+ _ => false,
  }
- },
- _ => {
- if !enum_path.global &&
- enum_path.segments.len() == 1 &&
- enum_path.segments[0].parameters.is_empty()
- {
- // NB: If enum_path is a single identifier,
- // this should not be reachable due to special
- // handling further above.
- //
- // However, previously a PatIdent got emitted
- // here, so we preserve the branch just in case.
- //
- // A rewrite of the logic in this function
- // would probably make this obvious.
- self.span_bug(enum_path.span,
- "ident only path should have been covered already");
- } else {
- pat = PatEnum(enum_path, Some(args));
- }
- }
+ });
+ if is_dotdot {
+ // This is a "top constructor only" pat
+ self.bump();
+ self.bump();
+ self.expect(&token::CloseDelim(token::Paren));
+ pat = PatEnum(enum_path, None);
+ } else {
+ let args = self.parse_enum_variant_seq(
+ &token::OpenDelim(token::Paren),
+ &token::CloseDelim(token::Paren),
+ seq_sep_trailing_allowed(token::Comma),
+ |p| p.parse_pat()
+ );
+ pat = PatEnum(enum_path, Some(args));
+ }
+ }
+ _ => {
+ if !enum_path.global &&
+ enum_path.segments.len() == 1 &&
+ enum_path.segments[0].parameters.is_empty()
+ {
+ // We expect an identifier, but due to
+ // `can_be_enum_or_struct` is true above,
+ // we reach here instead.
+ let tok_str = pprust::path_to_string(&enum_path);
+ self.span_fatal(
+ enum_path.span,
+ &format!("expected identifier, found enum or struct `{}`",
+ tok_str));
+ } else {
+ pat = PatEnum(enum_path, Some(Vec::new()));
  }
  }
  }

src/test/parse-fail/issue-22426.rs

@@ -0,0 +1,23 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub struct Foo<T>(T, T);
+
+impl<T> Foo<T> {
+ fn foo(&self) {
+ match *self {
+ // The error message is not ideal in this case, can we do
+ // better here?
+ Foo<T>(ref x, ref y) => {} //~ ERROR expected identifier, found enum or struct
+ }
+ }
+}
+
+fn main() {}

src/test/parse-fail/issue-22712.rs

@@ -0,0 +1,19 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+struct Foo<B> {
+ buffer: B
+}
+
+fn bar() {
+ let Foo<Vec<u8>> //~ ERROR expected identifier, found enum or struct
+}
+
+fn main() {}