Try to recover from unmatched delimiters in the parser

src/librustc_errors/emitter.rs

@@ -678,8 +678,8 @@ impl EmitterWriter {
         //   | |  something about `foo`
         //   | something about `fn foo()`
         annotations_position.sort_by(|a, b| {
-            // Decreasing order
-            a.1.len().cmp(&b.1.len()).reverse()
+            // Decreasing order. When `a` and `b` are the same length, prefer `Primary`.
+            (a.1.len(), !a.1.is_primary).cmp(&(b.1.len(), !b.1.is_primary)).reverse()
         });
 
         // Write the underlines.

src/librustc_metadata/cstore_impl.rs

@@ -465,7 +465,7 @@ impl cstore::CStore {
 
         let source_file = sess.parse_sess.source_map().new_source_file(source_name, def.body);
         let local_span = Span::new(source_file.start_pos, source_file.end_pos, NO_EXPANSION);
-        let body = source_file_to_stream(&sess.parse_sess, source_file, None);
+        let body = source_file_to_stream(&sess.parse_sess, source_file, None).0;
 
         // Mark the attrs as used
         let attrs = data.get_item_attrs(id.index, sess);

src/libsyntax/parse/lexer/mod.rs

@@ -66,6 +66,7 @@ pub struct StringReader<'a> {
     /// The raw source span which *does not* take `override_span` into account
     span_src_raw: Span,
     open_braces: Vec<(token::DelimToken, Span)>,
+    crate unmatched_braces: Vec<(token::DelimToken, Span)>,
     /// The type and spans for all braces
     ///
     /// Used only for error recovery when arriving to EOF with mismatched braces.
@@ -221,6 +222,7 @@ impl<'a> StringReader<'a> {
             span_src_raw: syntax_pos::DUMMY_SP,
             open_braces: Vec::new(),
             matching_delim_spans: Vec::new(),
+            unmatched_braces: Vec::new(),
             override_span,
             last_unclosed_found_span: None,
         }

src/libsyntax/parse/lexer/tokentrees.rs

@@ -49,8 +49,9 @@ impl<'a> StringReader<'a> {
             token::Eof => {
                 let msg = "this file contains an un-closed delimiter";
                 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, msg);
-                for &(_, sp) in &self.open_braces {
+                for &(tok, sp) in &self.open_braces {
                     err.span_label(sp, "un-closed delimiter");
+                    self.unmatched_braces.push((tok, sp));
                 }
 
                 if let Some((delim, _)) = self.open_braces.last() {
@@ -134,7 +135,7 @@ impl<'a> StringReader<'a> {
                             }
                             err.emit();
                         }
-                        self.open_braces.pop().unwrap();
+                        self.unmatched_braces.push(self.open_braces.pop().unwrap());
 
                         // If the incorrect delimiter matches an earlier opening
                         // delimiter, then don't consume it (it can be used to

src/libsyntax/parse/mod.rs

@@ -168,10 +168,13 @@ crate fn parse_stmt_from_source_str(name: FileName, source: String, sess: &Parse
     new_parser_from_source_str(sess, name, source).parse_stmt()
 }
 
-pub fn parse_stream_from_source_str(name: FileName, source: String, sess: &ParseSess,
-                                    override_span: Option<Span>)
-                                    -> TokenStream {
-    source_file_to_stream(sess, sess.source_map().new_source_file(name, source), override_span)
+pub fn parse_stream_from_source_str(
+    name: FileName,
+    source: String,
+    sess: &ParseSess,
+    override_span: Option<Span>,
+) -> TokenStream {
+    source_file_to_stream(sess, sess.source_map().new_source_file(name, source), override_span).0
 }
 
 // Create a new parser from a source string
@@ -191,26 +194,28 @@ pub fn new_parser_from_file<'a>(sess: &'a ParseSess, path: &Path) -> Parser<'a>
 /// Given a session, a crate config, a path, and a span, add
 /// the file at the given path to the source_map, and return a parser.
 /// On an error, use the given span as the source of the problem.
-crate fn new_sub_parser_from_file<'a>(sess: &'a ParseSess,
-                                    path: &Path,
-                                    directory_ownership: DirectoryOwnership,
-                                    module_name: Option<String>,
-                                    sp: Span) -> Parser<'a> {
+crate fn new_sub_parser_from_file<'a>(
+    sess: &'a ParseSess,
+    path: &Path,
+    directory_ownership: DirectoryOwnership,
+    module_name: Option<String>,
+    sp: Span,
+) -> Parser<'a> {
     let mut p = source_file_to_parser(sess, file_to_source_file(sess, path, Some(sp)));
     p.directory.ownership = directory_ownership;
     p.root_module_name = module_name;
     p
 }
 
 /// Given a source_file and config, return a parser
-fn source_file_to_parser(sess: & ParseSess, source_file: Lrc<SourceFile>) -> Parser {
+fn source_file_to_parser(sess: &ParseSess, source_file: Lrc<SourceFile>) -> Parser {
     let end_pos = source_file.end_pos;
-    let mut parser = stream_to_parser(sess, source_file_to_stream(sess, source_file, None));
-
+    let (tts, open_braces) = source_file_to_stream(sess, source_file, None);
+    let mut parser = stream_to_parser(sess, tts);
+    parser.open_braces = open_braces;
     if parser.token == token::Eof && parser.span.is_dummy() {
         parser.span = Span::new(end_pos, end_pos, parser.span.ctxt());
     }
-
     parser
 }
 
@@ -240,12 +245,15 @@ fn file_to_source_file(sess: &ParseSess, path: &Path, spanopt: Option<Span>)
 }
 
 /// Given a source_file, produce a sequence of token-trees
-pub fn source_file_to_stream(sess: &ParseSess,
-                             source_file: Lrc<SourceFile>,
-                             override_span: Option<Span>) -> TokenStream {
+pub fn source_file_to_stream(
+    sess: &ParseSess,
+    source_file: Lrc<SourceFile>,
+    override_span: Option<Span>,
+) -> (TokenStream, Vec<(token::DelimToken, Span)>) {
     let mut srdr = lexer::StringReader::new(sess, source_file, override_span);
     srdr.real_token();
-    panictry!(srdr.parse_all_token_trees())
+    let tt = panictry!(srdr.parse_all_token_trees());
+    (tt, srdr.unmatched_braces)
 }
 
 /// Given stream and the `ParseSess`, produce a parser

src/libsyntax/util/parser_testing.rs

@@ -22,7 +22,7 @@ use std::path::PathBuf;
 pub fn string_to_stream(source_str: String) -> TokenStream {
     let ps = ParseSess::new(FilePathMapping::empty());
     source_file_to_stream(&ps, ps.source_map()
-                             .new_source_file(PathBuf::from("bogofile").into(), source_str), None)
+                             .new_source_file(PathBuf::from("bogofile").into(), source_str), None).0
 }
 
 /// Map string to parser (via tts)

src/test/ui/augmented-assignments.nll.stderr

@@ -9,7 +9,7 @@ LL |       x   //~ error: use of moved value: `x`
 LL | |     //~^ value used here after move
 LL | |     +=
 LL | |     x;  //~ value moved here
-   | |     -
+   | |     ^
    | |     |
    | |_____move out of `x` occurs here
    |       borrow later used here

src/test/ui/parser-recovery-3.rs

@@ -0,0 +1,24 @@
+// Copyright 2018 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 A;
+
+impl A {
+    fn banana(&mut self) {
+        fn peach(this: &Self, foo: usize {
+        //~^ ERROR expected one of
+        //~| ERROR can't use type parameters from outer function
+        }
+    }
+    //~^ ERROR incorrect close delimiter
+    //~| ERROR expected expression
+}
+
+fn main() {}

src/test/ui/parser-recovery-3.stderr

@@ -0,0 +1,41 @@
+error: incorrect close delimiter: `}`
+  --> $DIR/parser-recovery-3.rs:19:5
+   |
+LL |     fn banana(&mut self) {
+   |                          - close delimiter possibly meant for this
+LL |         fn peach(this: &Self, foo: usize {
+   |                 - un-closed delimiter
+...
+LL |     }
+   |     ^ incorrect close delimiter
+
+error: expected one of `!`, `(`, `)`, `+`, `,`, `::`, or `<`, found `{`
+  --> $DIR/parser-recovery-3.rs:15:42
+   |
+LL |         fn peach(this: &Self, foo: usize {
+   |                 -                       -^ expected one of 7 possible tokens here
+   |                 |                       |
+   |                 |                       help: ...the missing `)` may belong here
+   |                 if you meant to close this...
+
+error: expected expression, found `)`
+  --> $DIR/parser-recovery-3.rs:19:5
+   |
+LL |     }
+   |     ^ expected expression
+
+error[E0401]: can't use type parameters from outer function
+  --> $DIR/parser-recovery-3.rs:15:25
+   |
+LL | impl A {
+   | ---- `Self` type implicitly declared here, by this `impl`
+LL |     fn banana(&mut self) {
+LL |         fn peach(this: &Self, foo: usize {
+   |                         ^^^^
+   |                         |
+   |                         use of type variable from outer function
+   |                         use a type here instead
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0401`.

src/test/ui/parser-recovery-4.rs

@@ -0,0 +1,21 @@
+// Copyright 2018 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.
+
+fn foo(_: usize) {}
+fn bar() {}
+
+fn main() {
+    let x = 1;
+    foo(x
+    bar()
+    //~^ ERROR expected one of
+    //~| ERROR expected one of
+}
+//~^ ERROR incorrect close delimiter

src/test/ui/parser-recovery-4.stderr

@@ -0,0 +1,34 @@
+error: incorrect close delimiter: `}`
+  --> $DIR/parser-recovery-4.rs:20:1
+   |
+LL | fn main() {
+   |           - close delimiter possibly meant for this
+LL |     let x = 1;
+LL |     foo(x
+   |        - un-closed delimiter
+...
+LL | }
+   | ^ incorrect close delimiter
+
+error: expected one of `!`, `)`, `,`, `.`, `::`, `?`, `{`, or an operator, found `bar`
+  --> $DIR/parser-recovery-4.rs:17:5
+   |
+LL |     foo(x
+   |        - -
+   |        | |
+   |        | expected one of 8 possible tokens here
+   |        | help: ...the missing `)` may belong here
+   |        if you meant to close this...
+LL |     bar()
+   |     ^^^ unexpected token
+
+error: expected one of `.`, `;`, `?`, `}`, or an operator, found `bar`
+  --> $DIR/parser-recovery-4.rs:17:5
+   |
+LL |     foo(x
+   |          - expected one of `.`, `;`, `?`, `}`, or an operator here
+LL |     bar()
+   |     ^^^ unexpected token
+
+error: aborting due to 3 previous errors
+

src/test/ui/resolve/token-error-correct-3.rs

@@ -20,21 +20,21 @@ pub mod raw {
     pub fn ensure_dir_exists<P: AsRef<Path>, F: FnOnce(&Path)>(path: P,
                                                                callback: F)
                                                                -> io::Result<bool> {
-        if !is_directory(path.as_ref()) { //~ ERROR: cannot find function `is_directory`
-            callback(path.as_ref(); //~ ERROR expected one of
-            fs::create_dir_all(path.as_ref()).map(|()| true) //~ ERROR: mismatched types
-            //~^ expected (), found enum `std::result::Result`
-            //~| expected type `()`
-            //~| found type `std::result::Result<bool, std::io::Error>`
-            //~| expected one of
-        } else { //~ ERROR: incorrect close delimiter: `}`
-            //~^ ERROR: expected one of
-            //~| unexpected token
+        if !is_directory(path.as_ref()) {
+            callback(path.as_ref();
+            //~^ ERROR expected one of
+            fs::create_dir_all(path.as_ref()).map(|()| true)
+        } else {
+            //~^ ERROR incorrect close delimiter: `}`
+            //~| ERROR expected one of
+            //~^^^^ ERROR mismatched types
             Ok(false);
         }
 
         panic!();
     }
+
+    fn is_directory<P: AsRef<Path>>(_: P) -> bool { true }
 }
 
 fn main() {}

src/test/ui/resolve/token-error-correct-3.stderr

@@ -1,47 +1,43 @@
 error: incorrect close delimiter: `}`
-  --> $DIR/token-error-correct-3.rs:30:9
+  --> $DIR/token-error-correct-3.rs:27:9
    |
-LL |         if !is_directory(path.as_ref()) { //~ ERROR: cannot find function `is_directory`
+LL |         if !is_directory(path.as_ref()) {
    |                                         - close delimiter possibly meant for this
-LL |             callback(path.as_ref(); //~ ERROR expected one of
+LL |             callback(path.as_ref();
    |                     - un-closed delimiter
 ...
-LL |         } else { //~ ERROR: incorrect close delimiter: `}`
+LL |         } else {
    |         ^ incorrect close delimiter
 
 error: expected one of `)`, `,`, `.`, `?`, or an operator, found `;`
   --> $DIR/token-error-correct-3.rs:24:35
    |
-LL |             callback(path.as_ref(); //~ ERROR expected one of
-   |                                   ^ expected one of `)`, `,`, `.`, `?`, or an operator here
+LL |             callback(path.as_ref();
+   |                     -             ^
+   |                     |             |
+   |                     |             expected one of `)`, `,`, `.`, `?`, or an operator here
+   |                     |             help: ...the missing `)` may belong here
+   |                     if you meant to close this...
 
 error: expected one of `.`, `;`, `?`, `}`, or an operator, found `)`
-  --> $DIR/token-error-correct-3.rs:30:9
+  --> $DIR/token-error-correct-3.rs:27:9
    |
-LL |             fs::create_dir_all(path.as_ref()).map(|()| true) //~ ERROR: mismatched types
+LL |             fs::create_dir_all(path.as_ref()).map(|()| true)
    |                                                             - expected one of `.`, `;`, `?`, `}`, or an operator here
-...
-LL |         } else { //~ ERROR: incorrect close delimiter: `}`
+LL |         } else {
    |         ^ unexpected token
 
-error[E0425]: cannot find function `is_directory` in this scope
-  --> $DIR/token-error-correct-3.rs:23:13
-   |
-LL |         if !is_directory(path.as_ref()) { //~ ERROR: cannot find function `is_directory`
-   |             ^^^^^^^^^^^^ not found in this scope
-
 error[E0308]: mismatched types
-  --> $DIR/token-error-correct-3.rs:25:13
+  --> $DIR/token-error-correct-3.rs:26:13
    |
-LL |             fs::create_dir_all(path.as_ref()).map(|()| true) //~ ERROR: mismatched types
+LL |             fs::create_dir_all(path.as_ref()).map(|()| true)
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^- help: try adding a semicolon: `;`
    |             |
    |             expected (), found enum `std::result::Result`
    |
    = note: expected type `()`
               found type `std::result::Result<bool, std::io::Error>`
 
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 
-Some errors occurred: E0308, E0425.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/resolve/token-error-correct.rs

@@ -12,6 +12,10 @@
 
 fn main() {
     foo(bar(;
-    //~^ ERROR: expected expression, found `;`
+    //~^ ERROR expected expression, found `;`
+    //~| ERROR expected one of
+    //~| ERROR cannot find function `foo` in this scope
+    //~| ERROR cannot find function `bar` in this scope
 }
-//~^ ERROR: incorrect close delimiter: `}`
+//~^ ERROR incorrect close delimiter: `}`
+//~| ERROR expected expression

src/test/ui/resolve/token-error-correct.stderr

@@ -1,19 +1,52 @@
 error: incorrect close delimiter: `}`
-  --> $DIR/token-error-correct.rs:16:1
+  --> $DIR/token-error-correct.rs:19:1
    |
 LL | fn main() {
    |           - close delimiter possibly meant for this
 LL |     foo(bar(;
    |            - un-closed delimiter
-LL |     //~^ ERROR: expected expression, found `;`
+...
 LL | }
    | ^ incorrect close delimiter
 
 error: expected expression, found `;`
   --> $DIR/token-error-correct.rs:14:13
    |
 LL |     foo(bar(;
-   |             ^ expected expression
+   |        -    ^
+   |        |    |
+   |        |    expected expression
+   |        |    help: ...the missing `)` may belong here
+   |        if you meant to close this...
 
-error: aborting due to 2 previous errors
+error: expected one of `)`, `,`, `.`, `?`, or an operator, found `;`
+  --> $DIR/token-error-correct.rs:14:13
+   |
+LL |     foo(bar(;
+   |            -^
+   |            ||
+   |            |expected one of `)`, `,`, `.`, `?`, or an operator here
+   |            |help: ...the missing `)` may belong here
+   |            if you meant to close this...
+
+error: expected expression, found `)`
+  --> $DIR/token-error-correct.rs:19:1
+   |
+LL | }
+   | ^ expected expression
+
+error[E0425]: cannot find function `foo` in this scope
+  --> $DIR/token-error-correct.rs:14:5
+   |
+LL |     foo(bar(;
+   |     ^^^ not found in this scope
+
+error[E0425]: cannot find function `bar` in this scope
+  --> $DIR/token-error-correct.rs:14:9
+   |
+LL |     foo(bar(;
+   |         ^^^ not found in this scope
+
+error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0425`.

src/test/ui/token/issue-10636-2.rs

@@ -13,9 +13,10 @@
 
 pub fn trace_option(option: Option<isize>) {
     option.map(|some| 42;
-                          //~^ ERROR: expected one of
+    //~^ ERROR expected one of
 
-} //~ ERROR: incorrect close delimiter
-//~^ ERROR: expected expression, found `)`
+}
+//~^ ERROR: incorrect close delimiter
+//~| ERROR expected expression
 
 fn main() {}

src/test/ui/token/issue-10636-2.stderr

@@ -6,19 +6,23 @@ LL | pub fn trace_option(option: Option<isize>) {
 LL |     option.map(|some| 42;
    |               - un-closed delimiter
 ...
-LL | } //~ ERROR: incorrect close delimiter
+LL | }
    | ^ incorrect close delimiter
 
 error: expected one of `)`, `,`, `.`, `?`, or an operator, found `;`
   --> $DIR/issue-10636-2.rs:15:25
    |
 LL |     option.map(|some| 42;
-   |                         ^ expected one of `)`, `,`, `.`, `?`, or an operator here
+   |               -         ^
+   |               |         |
+   |               |         expected one of `)`, `,`, `.`, `?`, or an operator here
+   |               |         help: ...the missing `)` may belong here
+   |               if you meant to close this...
 
 error: expected expression, found `)`
   --> $DIR/issue-10636-2.rs:18:1
    |
-LL | } //~ ERROR: incorrect close delimiter
+LL | }
    | ^ expected expression
 
 error: aborting due to 3 previous errors