fix-it hints: insert_before vs insert_after

The API for adding "insert text" fix-it hints was unclear
about exactly where the text should be inserted relative
to the given insertion point.

This patch clarifies things by renaming the pertinent methods from
  richloc.add_fixit_insert
to
  richloc.add_fixit_insert_before
and adding:
  richloc.add_fixit_insert_after

The latter allows us to consolidate some failure-handling into
class rich_location, rather than having to have every such diagnostic
check for it.

The patch also adds a description of how fix-it hints work to the
comment for class rich_location within libcpp/include/line-map.h.

gcc/c-family/ChangeLog:
	* c-common.c (warn_logical_not_parentheses): Replace
	rich_location::add_fixit_insert calls with add_fixit_insert_before
	and add_fixit_insert_after, eliminating the "next_loc" calculation.

gcc/c/ChangeLog:
	* c-parser.c (c_parser_declaration_or_fndef): Update for renaming
	of add_fixit_insert to add_fixit_insert_before.

gcc/cp/ChangeLog:
	* parser.c (cp_parser_class_specifier_1): Update for renaming of
	add_fixit_insert to add_fixit_insert_before.
	(cp_parser_class_head): Likewise.

gcc/ChangeLog:
	* diagnostic-show-locus.c (selftest::test_one_liner_fixit_insert):
	Rename to...
	(selftest::test_one_liner_fixit_insert_before): ...this, and update
	for renaming of add_fixit_insert to add_fixit_insert_before.
	(selftest::test_one_liner_fixit_insert_after): New function.
	(selftest::test_one_liner_fixit_validation_adhoc_locations):
	Update for renaming of add_fixit_insert to
	add_fixit_insert_before.
	(selftest::test_one_liner_many_fixits): Likewise.
	(selftest::test_diagnostic_show_locus_one_liner): Update for
	renaming, call new test function.
	(selftest::test_diagnostic_show_locus_fixit_lines): Update for
	renaming of add_fixit_insert to add_fixit_insert_before.
	(selftest::test_fixit_consolidation): Likewise.
	* diagnostic.c (selftest::test_print_parseable_fixits_insert):
	Likewise.
	* edit-context.c (selftest::test_applying_fixits_insert): Rename
	to...
	(selftest::test_applying_fixits_insert_before): ...this.
	(selftest::test_applying_fixits_insert): Update for renaming of
	add_fixit_insert to add_fixit_insert_before.
	(selftest::test_applying_fixits_insert_after): New function.
	(selftest::test_applying_fixits_insert_after_at_line_end): New
	function.
	(selftest::test_applying_fixits_insert_after_failure): New
	function.
	(selftest::test_applying_fixits_multiple): Update for renaming of
	add_fixit_insert to add_fixit_insert_before.
	(selftest::change_line): Likewise.
	(selftest::test_applying_fixits_unreadable_file): Likewise.
	(selftest::test_applying_fixits_line_out_of_range): Likewise.
	(selftest::test_applying_fixits_column_validation): Likewise.
	(selftest::test_applying_fixits_column_validation): Likewise.
	(selftest::edit_context_c_tests): Update for renamed test
	function; call new test functions.

gcc/testsuite/ChangeLog:
	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
	(test_show_locus): Replace rich_location::add_fixit_insert calls
	with add_fixit_insert_before and add_fixit_insert_after.

libcpp/ChangeLog:
	* include/line-map.h (class rich_location): Add description of
	fix-it hints to leading comment.
	(rich_location::add_fixit_insert): Rename both overloaded methods
	to..
	(rich_location::add_fixit_insert_before): ...this, updating their
	comments.
	(rich_location::add_fixit_insert_after): Two new overloaded
	methods.
	(rich_location::stop_supporting_fixits): New method.
	* line-map.c (rich_location::add_fixit_insert): Rename both
	overloaded methods to..
	(rich_location::add_fixit_insert_before): ...this, updating their
	comments.
	(rich_location::add_fixit_insert_after): Two new methods.
	(rich_location::reject_impossible_fixit): Split out
	failure-handling into...
	(rich_location::stop_supporting_fixits): New method.

From-SVN: r240115

3 files changed, 169 insertions, 17 deletions

diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index 792f76a..95e12a9 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,3 +1,23 @@
+2016-09-13  David Malcolm  <dmalcolm@redhat.com>
+
+	* include/line-map.h (class rich_location): Add description of
+	fix-it hints to leading comment.
+	(rich_location::add_fixit_insert): Rename both overloaded methods
+	to..
+	(rich_location::add_fixit_insert_before): ...this, updating their
+	comments.
+	(rich_location::add_fixit_insert_after): Two new overloaded
+	methods.
+	(rich_location::stop_supporting_fixits): New method.
+	* line-map.c (rich_location::add_fixit_insert): Rename both
+	overloaded methods to..
+	(rich_location::add_fixit_insert_before): ...this, updating their
+	comments.
+	(rich_location::add_fixit_insert_after): Two new methods.
+	(rich_location::reject_impossible_fixit): Split out
+	failure-handling into...
+	(rich_location::stop_supporting_fixits): New method.
+
 2016-09-02  David Malcolm  <dmalcolm@redhat.com>
 
 	* include/line-map.h (rich_location::seen_impossible_fixit_p): New
diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index 6b3c474..939bfcc 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -1484,7 +1484,84 @@ class fixit_hint;
    - range 0 is at the "%s" with start = caret = "%" and finish at
      the "s".
    - range 1 has start/finish covering the "101" and is not flagged for
-     caret printing; it is perhaps at the start of "101".  */
+     caret printing; it is perhaps at the start of "101".
+
+
+   Fix-it hints
+   ------------
+
+   Rich locations can also contain "fix-it hints", giving suggestions
+   for the user on how to edit their code to fix a problem.  These
+   can be expressed as insertions, replacements, and removals of text.
+   The edits by default are relative to the zeroth range within the
+   rich_location, but optionally they can be expressed relative to
+   other locations (using various overloaded methods of the form
+   rich_location::add_fixit_*).
+
+   For example:
+
+   Example F: fix-it hint: insert_before
+   *************************************
+      ptr = arr[0];
+	    ^~~~~~
+	    &
+   This rich location has a single range (range 0) covering "arr[0]",
+   with the caret at the start.  The rich location has a single
+   insertion fix-it hint, inserted before range 0, added via
+     richloc.add_fixit_insert_before ("&");
+
+   Example G: multiple fix-it hints: insert_before and insert_after
+   ****************************************************************
+      #define FN(ARG0, ARG1, ARG2) fn(ARG0, ARG1, ARG2)
+				      ^~~~  ^~~~  ^~~~
+				      (   ) (   ) (   )
+   This rich location has three ranges, covering "arg0", "arg1",
+   and "arg2", all with caret-printing enabled.
+   The rich location has 6 insertion fix-it hints: each arg
+   has a pair of insertion fix-it hints, suggesting wrapping
+   them with parentheses: one a '(' inserted before,
+   the other a ')' inserted after, added via
+     richloc.add_fixit_insert_before (LOC, "(");
+   and
+     richloc.add_fixit_insert_after (LOC, ")");
+
+   Example H: fix-it hint: removal
+   *******************************
+     struct s {int i};;
+		      ^
+		      -
+   This rich location has a single range at the stray trailing
+   semicolon, along with a single removal fix-it hint, covering
+   the same range, added via:
+     richloc.add_fixit_remove ();
+
+   Example I: fix-it hint: replace
+   *******************************
+      c = s.colour;
+	    ^~~~~~
+	    color
+   This rich location has a single range (range 0) covering "colour",
+   and a single "replace" fix-it hint, covering the same range,
+   added via
+     richloc.add_fixit_replace ("color");
+
+   Adding a fix-it hint can fail: for example, attempts to insert content
+   at the transition between two line maps may fail due to there being no
+   source_location (aka location_t) value to express the new location.
+
+   Attempts to add a fix-it hint within a macro expansion will fail.
+
+   The rich_location API handles these failures gracefully, so that
+   diagnostics can attempt to add fix-it hints without each needing
+   extensive checking.
+
+   Fix-it hints within a rich_location are "atomic": if any hints can't
+   be applied, none of them will be (tracked by the m_seen_impossible_fixit
+   flag), and no fix-its hints will be displayed for that rich_location.
+   This implies that diagnostic messages need to be worded in such a way
+   that they make sense whether or not the fix-it hints are displayed,
+   or that richloc.seen_impossible_fixit_p () should be checked before
+   issuing the diagnostics.  */
 
 class rich_location
 {
@@ -1522,14 +1599,25 @@ class rich_location
 
   /* Methods for adding insertion fix-it hints.  */
 
-  /* Suggest inserting NEW_CONTENT at the primary range's caret.  */
+  /* Suggest inserting NEW_CONTENT immediately before the primary
+     range's start.  */
   void
-  add_fixit_insert (const char *new_content);
+  add_fixit_insert_before (const char *new_content);
 
-  /* Suggest inserting NEW_CONTENT at WHERE.  */
+  /* Suggest inserting NEW_CONTENT immediately before the start of WHERE.  */
   void
-  add_fixit_insert (source_location where,
-		    const char *new_content);
+  add_fixit_insert_before (source_location where,
+			   const char *new_content);
+
+  /* Suggest inserting NEW_CONTENT immediately after the end of the primary
+     range.  */
+  void
+  add_fixit_insert_after (const char *new_content);
+
+  /* Suggest inserting NEW_CONTENT immediately after the end of WHERE.  */
+  void
+  add_fixit_insert_after (source_location where,
+			  const char *new_content);
 
   /* Methods for adding removal fix-it hints.  */
 
@@ -1571,6 +1659,7 @@ class rich_location
 
 private:
   bool reject_impossible_fixit (source_location where);
+  void stop_supporting_fixits ();
   void add_fixit (fixit_hint *hint);
 
 public:
diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index f69c60c..742af0a 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -2109,26 +2109,61 @@ rich_location::set_range (line_maps * /*set*/, unsigned int idx,
 /* Methods for adding insertion fix-it hints.  */
 
 /* Add a fixit-hint, suggesting insertion of NEW_CONTENT
-   at the primary range's caret location.  */
+   immediately before the primary range's start location.  */
 
 void
-rich_location::add_fixit_insert (const char *new_content)
+rich_location::add_fixit_insert_before (const char *new_content)
 {
-  add_fixit_insert (get_loc (), new_content);
+  add_fixit_insert_before (get_loc (), new_content);
 }
 
 /* Add a fixit-hint, suggesting insertion of NEW_CONTENT
-   at WHERE.  */
+   immediately before the start of WHERE.  */
 
 void
-rich_location::add_fixit_insert (source_location where,
-				 const char *new_content)
+rich_location::add_fixit_insert_before (source_location where,
+					const char *new_content)
 {
-  where = get_pure_location (m_line_table, where);
+  source_location start = get_range_from_loc (m_line_table, where).m_start;
 
-  if (reject_impossible_fixit (where))
+  if (reject_impossible_fixit (start))
     return;
-  add_fixit (new fixit_insert (where, new_content));
+  add_fixit (new fixit_insert (start, new_content));
+}
+
+/* Add a fixit-hint, suggesting insertion of NEW_CONTENT
+   immediately after the primary range's end-point.  */
+
+void
+rich_location::add_fixit_insert_after (const char *new_content)
+{
+  add_fixit_insert_after (get_loc (), new_content);
+}
+
+/* Add a fixit-hint, suggesting insertion of NEW_CONTENT
+   immediately after the end-point of WHERE.  */
+
+void
+rich_location::add_fixit_insert_after (source_location where,
+				       const char *new_content)
+{
+  source_location finish = get_range_from_loc (m_line_table, where).m_finish;
+
+  if (reject_impossible_fixit (finish))
+    return;
+
+  source_location next_loc
+    = linemap_position_for_loc_and_offset (m_line_table, finish, 1);
+
+  /* linemap_position_for_loc_and_offset can fail, if so, it returns
+     its input value.  */
+  if (next_loc == finish)
+    {
+      stop_supporting_fixits ();
+      return;
+    }
+
+  add_fixit (new fixit_insert (next_loc, new_content));
 }
 
 /* Methods for adding removal fix-it hints.  */
@@ -2278,14 +2313,22 @@ rich_location::reject_impossible_fixit (source_location where)
   /* Otherwise we have an attempt to add a fix-it with an "awkward"
      location: either one that we can't obtain column information
      for (within an ordinary map), or one within a macro expansion.  */
+  stop_supporting_fixits ();
+  return true;
+}
+
+/* Mark this rich_location as not supporting fixits, purging any that were
+   already added.  */
+
+void
+rich_location::stop_supporting_fixits ()
+{
   m_seen_impossible_fixit = true;
 
   /* Purge the rich_location of any fix-its that were already added. */
   for (unsigned int i = 0; i < m_fixit_hints.count (); i++)
     delete get_fixit_hint (i);
   m_fixit_hints.truncate (0);
-
-  return true;
 }
 
 /* Add HINT to the fix-it hints in this rich_location.  */