Do not point at delim spans for complete correct blocks

Author: estebank

src/libsyntax/parse/lexer/tokentrees.rs

@@ -97,7 +97,15 @@ impl<'a> StringReader<'a> {
                     // Correct delimiter.
                     token::CloseDelim(d) if d == delim => {
                         let (open_brace, open_brace_span) = self.open_braces.pop().unwrap();
-                        self.matching_delim_spans.push((open_brace, open_brace_span, self.span));
+                        if self.open_braces.len() == 0 {
+                            // Clear up these spans to avoid suggesting them as we've found
+                            // properly matched delimiters so far for an entire block.
+                            self.matching_delim_spans.clear();
+                        } else {
+                            self.matching_delim_spans.push(
+                                (open_brace, open_brace_span, self.span),
+                            );
+                        }
                         // Parse the close delimiter.
                         self.real_token();
                     }

src/test/ui/parser/unmatched-delimiter-at-end-of-file.rs

@@ -0,0 +1,11 @@
+struct S {
+    x: usize,
+    y: usize,
+}
+
+fn main() {
+    S { x: 4,
+        y: 5 };
+}
+
+fn foo() { //~ ERROR this file contains an un-closed delimiter

src/test/ui/parser/unmatched-delimiter-at-end-of-file.stderr

@@ -0,0 +1,8 @@
+error: this file contains an un-closed delimiter
+  --> $DIR/unmatched-delimiter-at-end-of-file.rs:11:64
+   |
+LL | fn foo() { //~ ERROR this file contains an un-closed delimiter
+   |          - un-closed delimiter                                 ^
+
+error: aborting due to previous error
+