rollup merge of #20424: jroesch/tuple-struct-where-clause-fix

Fixes #17904. All the cases that I believe we should support are detailed in the test case, let me know if there is there is any more desired behavior. cc @japaric.

r? @nikomatsakis or whoever is appropriate.

src/libsyntax/parse/parser.rs

@@ -4885,67 +4885,116 @@ fn parse_item_struct(&mut self) -> ItemInfo {
             self.span_err(ty.span, "`virtual` structs have been removed from the language");
         }
 
-        self.parse_where_clause(&mut generics);
+        // There is a special case worth noting here, as reported in issue #17904.
+        // If we are parsing a tuple struct it is the case that the where clause
+        // should follow the field list. Like so:
+        //
+        // struct Foo<T>(T) where T: Copy;
+        //
+        // If we are parsing a normal record-style struct it is the case
+        // that the where clause comes before the body, and after the generics.
+        // So if we look ahead and see a brace or a where-clause we begin
+        // parsing a record style struct.
+        //
+        // Otherwise if we look ahead and see a paren we parse a tuple-style
+        // struct.
+
+        let (fields, ctor_id) = if self.token.is_keyword(keywords::Where) {
+            self.parse_where_clause(&mut generics);
+            if self.eat(&token::Semi) {
+                // If we see a: `struct Foo<T> where T: Copy;` style decl.
+                (Vec::new(), Some(ast::DUMMY_NODE_ID))
+            } else {
+                // If we see: `struct Foo<T> where T: Copy { ... }`
+                (self.parse_record_struct_body(&class_name), None)
+            }
+        // No `where` so: `struct Foo<T>;`
+        } else if self.eat(&token::Semi) {
+            (Vec::new(), Some(ast::DUMMY_NODE_ID))
+        // Record-style struct definition
+        } else if self.token == token::OpenDelim(token::Brace) {
+            let fields = self.parse_record_struct_body(&class_name);
+            (fields, None)
+        // Tuple-style struct definition with optional where-clause.
+        } else {
+            let fields = self.parse_tuple_struct_body(&class_name, &mut generics);
+            (fields, Some(ast::DUMMY_NODE_ID))
+        };
 
-        let mut fields: Vec<StructField>;
-        let is_tuple_like;
+        (class_name,
+         ItemStruct(P(ast::StructDef {
+             fields: fields,
+             ctor_id: ctor_id,
+         }), generics),
+         None)
+    }
 
+    pub fn parse_record_struct_body(&mut self, class_name: &ast::Ident) -> Vec<StructField> {
+        let mut fields = Vec::new();
         if self.eat(&token::OpenDelim(token::Brace)) {
-            // It's a record-like struct.
-            is_tuple_like = false;
-            fields = Vec::new();
             while self.token != token::CloseDelim(token::Brace) {
                 fields.push(self.parse_struct_decl_field(true));
             }
+
             if fields.len() == 0 {
                 self.fatal(format!("unit-like struct definition should be \
-                                    written as `struct {};`",
-                                   token::get_ident(class_name))[]);
+                    written as `struct {};`",
+                    token::get_ident(class_name.clone()))[]);
             }
+
             self.bump();
-        } else if self.check(&token::OpenDelim(token::Paren)) {
-            // It's a tuple-like struct.
-            is_tuple_like = true;
-            fields = self.parse_unspanned_seq(
+        } else {
+            let token_str = self.this_token_to_string();
+            self.fatal(format!("expected `where`, or `{}` after struct \
+                                name, found `{}`", "{",
+                                token_str)[]);
+        }
+
+        fields
+    }
+
+    pub fn parse_tuple_struct_body(&mut self,
+                                   class_name: &ast::Ident,
+                                   generics: &mut ast::Generics)
+                                   -> Vec<StructField> {
+        // This is the case where we find `struct Foo<T>(T) where T: Copy;`
+        if self.check(&token::OpenDelim(token::Paren)) {
+            let fields = self.parse_unspanned_seq(
                 &token::OpenDelim(token::Paren),
                 &token::CloseDelim(token::Paren),
                 seq_sep_trailing_allowed(token::Comma),
                 |p| {
-                let attrs = p.parse_outer_attributes();
-                let lo = p.span.lo;
-                let struct_field_ = ast::StructField_ {
-                    kind: UnnamedField(p.parse_visibility()),
-                    id: ast::DUMMY_NODE_ID,
-                    ty: p.parse_ty_sum(),
-                    attrs: attrs,
-                };
-                spanned(lo, p.span.hi, struct_field_)
-            });
+                    let attrs = p.parse_outer_attributes();
+                    let lo = p.span.lo;
+                    let struct_field_ = ast::StructField_ {
+                        kind: UnnamedField(p.parse_visibility()),
+                        id: ast::DUMMY_NODE_ID,
+                        ty: p.parse_ty_sum(),
+                        attrs: attrs,
+                    };
+                    spanned(lo, p.span.hi, struct_field_)
+                });
+
             if fields.len() == 0 {
                 self.fatal(format!("unit-like struct definition should be \
-                                    written as `struct {};`",
-                                   token::get_ident(class_name))[]);
+                    written as `struct {};`",
+                    token::get_ident(class_name.clone()))[]);
             }
+
+            self.parse_where_clause(generics);
             self.expect(&token::Semi);
-        } else if self.eat(&token::Semi) {
-            // It's a unit-like struct.
-            is_tuple_like = true;
-            fields = Vec::new();
+            fields
+        // This is the case where we just see struct Foo<T> where T: Copy;
+        } else if self.token.is_keyword(keywords::Where) {
+            self.parse_where_clause(generics);
+            self.expect(&token::Semi);
+            Vec::new()
+        // This case is where we see: `struct Foo<T>;`
         } else {
             let token_str = self.this_token_to_string();
-            self.fatal(format!("expected `{}`, `(`, or `;` after struct \
-                                name, found `{}`", "{",
-                               token_str)[])
+            self.fatal(format!("expected `where`, `{}`, `(`, or `;` after struct \
+                name, found `{}`", "{", token_str)[]);
         }
-
-        let _ = ast::DUMMY_NODE_ID;  // FIXME: Workaround for crazy bug.
-        let new_id = ast::DUMMY_NODE_ID;
-        (class_name,
-         ItemStruct(P(ast::StructDef {
-             fields: fields,
-             ctor_id: if is_tuple_like { Some(new_id) } else { None },
-         }), generics),
-         None)
     }
 
     /// Parse a structure field declaration

src/libsyntax/print/pprust.rs

@@ -1056,7 +1056,6 @@ pub fn print_struct(&mut self,
                         span: codemap::Span) -> IoResult<()> {
         try!(self.print_ident(ident));
         try!(self.print_generics(generics));
-        try!(self.print_where_clause(generics));
         if ast_util::struct_def_is_tuple_like(struct_def) {
             if !struct_def.fields.is_empty() {
                 try!(self.popen());
@@ -1075,10 +1074,12 @@ pub fn print_struct(&mut self,
                 ));
                 try!(self.pclose());
             }
+            try!(self.print_where_clause(generics));
             try!(word(&mut self.s, ";"));
             try!(self.end());
             self.end() // close the outer-box
         } else {
+            try!(self.print_where_clause(generics));
             try!(self.nbsp());
             try!(self.bopen());
             try!(self.hardbreak_if_not_bol());

src/test/compile-fail/issue-17904.rs

+// Copyright 2014 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 Baz<U> where U: Eq(U); //This is parsed as the new Fn* style parenthesis syntax.
+struct Baz<U> where U: Eq(U) -> R; // Notice this parses as well.
+struct Baz<U>(U) where U: Eq; // This rightfully signals no error as well.
+struct Foo<T> where T: Copy, (T); //~ ERROR unexpected token in `where` clause
+struct Bar<T> { x: T } where T: Copy //~ ERROR expected item, found `where`
+
+fn main() {}

src/test/compile-fail/unsized.rs

@@ -10,7 +10,7 @@
 
 // Test syntax checks for `type` keyword.
 
-struct S1 for type; //~ ERROR expected `{`, `(`, or `;` after struct name, found `for`
+struct S1 for type; //~ ERROR expected `where`, `{`, `(`, or `;` after struct name, found `for`
 
 pub fn main() {
 }

src/test/run-pass/issue-17904.rs

+// Copyright 2014 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<T> where T: Copy;
+struct Bar<T>(T) where T: Copy;
+struct Bleh<T, U>(T, U) where T: Copy, U: Sized;
+struct Baz<T> where T: Copy {
+    field: T
+}
+
+fn main() {}