C/C++: add fix-it hints for various missing symbols

The patch improves our C/C++ frontends' handling of missing
symbols, by making c_parser_require and cp_parser_require use
"better" locations for the diagnostic, and insert fix-it hints,
under certain circumstances (see the comments in the patch for
full details).

For example, for this code with a missing semicolon:

  $ cat test.c
  int missing_semicolon (void)
  {
    return 42
  }

  trunk currently emits:

  test.c:4:1: error: expected ';' before '}' token
   }
   ^

This patch adds a fix-it hint for the missing semicolon, and puts
the error at the location of the missing semicolon, printing the
followup token as a secondary location:

  test.c:3:12: error: expected ';' before '}' token
     return 42
              ^
              ;
   }
   ~

More examples can be seen in the test cases.

gcc/c-family/ChangeLog:
	* c-common.c (enum missing_token_insertion_kind): New enum.
	(get_missing_token_insertion_kind): New function.
	(maybe_suggest_missing_token_insertion): New function.
	* c-common.h (maybe_suggest_missing_token_insertion): New decl.

gcc/c/ChangeLog:
	* c-parser.c (c_parser_require): Add "type_is_unique" param and
	use it to guard calls to maybe_suggest_missing_token_insertion.
	(c_parser_parms_list_declarator): Override default value of new
	"type_is_unique" param to c_parser_require.
	(c_parser_asm_statement): Likewise.
	* c-parser.h (c_parser_require): Add "type_is_unique" param,
	defaulting to true.

gcc/cp/ChangeLog:
	* parser.c (get_required_cpp_ttype): New function.
	(cp_parser_error_1): Call it, using the result to call
	maybe_suggest_missing_token_insertion.

gcc/testsuite/ChangeLog:
	* c-c++-common/cilk-plus/AN/parser_errors.c: Update expected
	output to reflect changes to reported locations of missing
	symbols.
	* c-c++-common/cilk-plus/AN/parser_errors2.c: Likewise.
	* c-c++-common/cilk-plus/AN/parser_errors3.c: Likewise.
	* c-c++-common/cilk-plus/AN/pr61191.c: Likewise.
	* c-c++-common/gomp/pr63326.c: Likewise.
	* c-c++-common/missing-close-symbol.c: Likewise, also update for
	new fix-it hints.
	* c-c++-common/missing-symbol.c: Likewise, also add test coverage
	for missing colon in ternary operator.
	* g++.dg/cpp1y/digit-sep-neg.C: Likewise.
	* g++.dg/cpp1y/pr65202.C: Likewise.
	* g++.dg/missing-symbol-2.C: New test case.
	* g++.dg/other/do1.C: Update expected output to reflect
	changes to reported locations of missing symbols.
	* g++.dg/parse/error11.C: Likewise.
	* g++.dg/template/error11.C: Likewise.
	* gcc.dg/missing-symbol-2.c: New test case.
	* gcc.dg/missing-symbol-3.c: New test case.
	* gcc.dg/noncompile/940112-1.c: Update expected output to reflect
	changes to reported locations of missing symbols.
	* gcc.dg/noncompile/971104-1.c: Likewise.
	* obj-c++.dg/exceptions-6.mm: Likewise.
	* obj-c++.dg/pr48187.mm: Likewise.
	* objc.dg/exceptions-6.m: Likewise.

From-SVN: r253690

1 files changed, 48 insertions, 3 deletions

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index b668b59..810e2b7 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -2788,6 +2788,40 @@ get_matching_symbol (required_token token_desc)
     }
 }
 
+/* Attempt to convert TOKEN_DESC from a required_token to an
+   enum cpp_ttype, returning CPP_EOF if there is no good conversion.  */
+
+static enum cpp_ttype
+get_required_cpp_ttype (required_token token_desc)
+{
+  switch (token_desc)
+    {
+    case RT_SEMICOLON:
+      return CPP_SEMICOLON;
+    case RT_OPEN_PAREN:
+      return CPP_OPEN_PAREN;
+    case RT_CLOSE_BRACE:
+      return CPP_CLOSE_BRACE;
+    case RT_OPEN_BRACE:
+      return CPP_OPEN_BRACE;
+    case RT_CLOSE_SQUARE:
+      return CPP_CLOSE_SQUARE;
+    case RT_OPEN_SQUARE:
+      return CPP_OPEN_SQUARE;
+    case RT_COMMA:
+      return CPP_COMMA;
+    case RT_COLON:
+      return CPP_COLON;
+    case RT_CLOSE_PAREN:
+      return CPP_CLOSE_PAREN;
+
+    default:
+      /* Use CPP_EOF as a "no completions possible" code.  */
+      return CPP_EOF;
+    }
+}
+
+
 /* Subroutine of cp_parser_error and cp_parser_required_error.
 
    Issue a diagnostic of the form
@@ -2799,9 +2833,12 @@ get_matching_symbol (required_token token_desc)
    This bypasses the check for tentative passing, and potentially
    adds material needed by cp_parser_required_error.
 
-   If MISSING_TOKEN_DESC is not RT_NONE, and MATCHING_LOCATION is not
-   UNKNOWN_LOCATION, then we have an unmatched symbol at
-   MATCHING_LOCATION; highlight this secondary location.  */
+   If MISSING_TOKEN_DESC is not RT_NONE, then potentially add fix-it hints
+   suggesting insertion of the missing token.
+
+   Additionally, if MATCHING_LOCATION is not UNKNOWN_LOCATION, then we
+   have an unmatched symbol at MATCHING_LOCATION; highlight this secondary
+   location.  */
 
 static void
 cp_parser_error_1 (cp_parser* parser, const char* gmsgid,
@@ -2840,6 +2877,14 @@ cp_parser_error_1 (cp_parser* parser, const char* gmsgid,
 
   if (missing_token_desc != RT_NONE)
     {
+      /* Potentially supply a fix-it hint, suggesting to add the
+	 missing token immediately after the *previous* token.
+	 This may move the primary location within richloc.  */
+      enum cpp_ttype ttype = get_required_cpp_ttype (missing_token_desc);
+      location_t prev_token_loc
+	= cp_lexer_previous_token (parser->lexer)->location;
+      maybe_suggest_missing_token_insertion (&richloc, ttype, prev_token_loc);
+
       /* If matching_location != UNKNOWN_LOCATION, highlight it.
 	 Attempt to consolidate diagnostics by printing it as a
 	secondary range within the main diagnostic.  */