[PATCH 2/4] PR c++/62314: add fixit hint for "expected ';' after class definition"

[David Malcolm <dmalcolm at redhat dot com>]

Looking over the discussion of missing semicolons in
  "Quality of Implementation and Attention to Detail"
within
  http://clang.llvm.org/diagnostics.html
and comparing with
  https://gcc.gnu.org/wiki/ClangDiagnosticsComparison
I noticed that of the cases we do handle [1], there's room for
improvement; we currently emit:

test.c:2:11: error: expected ';' after struct definition
 struct a {}
           ^

whereas clang reportedly emits:

test.c:2:12: error: expected ';' after struct
 struct a {}
            ^
            ;

(note the offset of the location, and the fix-it hint)

The following patch gives us the latter, more readable output.

Arguably not a bug fix (PR 62314 is more of a catch-all
for adding fix-its), but it's low-risk and a user-visible
improvement.

Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu;
adds 15 new PASS results to g++.sum.

OK for trunk in stage 3?

[1] I've also filed PR c++/68970 about a case given on the clang
page that we still don't handle.

gcc/cp/ChangeLog:
	PR c++/62314
	* parser.c (cp_parser_class_specifier_1): When reporting
	missing semicolons, use a fixit-hint to suggest insertion
	of a semicolon immediately after the closing brace,
	offsetting the reported column accordingly.

gcc/testsuite/ChangeLog:
	PR c++/62314
	* gcc/testsuite/g++.dg/parse/error5.C: Update column
	number of missing semicolon error.
	* g++.dg/pr62314-2.C: New test case.
---
 gcc/cp/parser.c                     | 19 ++++++++++++++++---
 gcc/testsuite/g++.dg/parse/error5.C |  2 +-
 gcc/testsuite/g++.dg/pr62314-2.C    | 22 ++++++++++++++++++++++
 3 files changed, 39 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/pr62314-2.C

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 2a688b2..c7b0aec 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -21287,17 +21287,30 @@ cp_parser_class_specifier_1 (cp_parser* parser)
        closing brace.  */
     if (closing_brace && TYPE_P (type) && want_semicolon)
       {
+	/* Locate the closing brace.  */
 	cp_token_position prev
 	  = cp_lexer_previous_token_position (parser->lexer);
 	cp_token *prev_token = cp_lexer_token_at (parser->lexer, prev);
 	location_t loc = prev_token->location;
 
+	/* We want to suggest insertion of a ';' immediately *after* the
+	   closing brace, so, if we can, offset the location by 1 column.  */
+	location_t next_loc = loc;
+	if (!linemap_location_from_macro_expansion_p (line_table, loc))
+	  next_loc = linemap_position_for_loc_and_offset (line_table, loc, 1);
+
+	rich_location richloc (line_table, next_loc);
+	richloc.add_fixit_insert (next_loc, ";");
+
 	if (CLASSTYPE_DECLARED_CLASS (type))
-	  error_at (loc, "expected %<;%> after class definition");
+	  error_at_rich_loc (&richloc,
+			     "expected %<;%> after class definition");
 	else if (TREE_CODE (type) == RECORD_TYPE)
-	  error_at (loc, "expected %<;%> after struct definition");
+	  error_at_rich_loc (&richloc,
+			     "expected %<;%> after struct definition");
 	else if (TREE_CODE (type) == UNION_TYPE)
-	  error_at (loc, "expected %<;%> after union definition");
+	  error_at_rich_loc (&richloc,
+			     "expected %<;%> after union definition");
 	else
 	  gcc_unreachable ();
 
diff --git a/gcc/testsuite/g++.dg/parse/error5.C b/gcc/testsuite/g++.dg/parse/error5.C
index eb1f9c7..d14a476 100644
--- a/gcc/testsuite/g++.dg/parse/error5.C
+++ b/gcc/testsuite/g++.dg/parse/error5.C
@@ -13,7 +13,7 @@ class Foo { int foo() return 0; } };
 // need make cp_parser_error() report more accurate column numbers.
 // { dg-error "30:expected '\{' at end of input" "brace" { target *-*-* } 4 }
 
-// { dg-error "33:expected ';' after class definition" "semicolon" {target *-*-* } 4 }
+// { dg-error "34:expected ';' after class definition" "semicolon" {target *-*-* } 4 }
 
 // { dg-error "35:expected declaration before '\}' token" "declaration" {target *-*-* } 4 }
 
diff --git a/gcc/testsuite/g++.dg/pr62314-2.C b/gcc/testsuite/g++.dg/pr62314-2.C
new file mode 100644
index 0000000..deb0cb7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr62314-2.C
@@ -0,0 +1,22 @@
+// { dg-options "-fdiagnostics-show-caret" }
+
+template<class T>
+class a {} // { dg-error "11: expected .;. after class definition" }
+class temp {};
+a<temp> b;
+struct b {
+} // { dg-error "2: expected .;. after struct definition" }
+
+/* Verify that we emit fixit hints.  */
+
+/* { dg-begin-multiline-output "" }
+ class a {}
+           ^
+           ;
+   { dg-end-multiline-output "" } */
+
+/* { dg-begin-multiline-output "" }
+ }
+  ^
+  ;
+   { dg-end-multiline-output "" } */
-- 
1.8.5.3