diagnostics: support compact printing of secondary locations

gcc/ChangeLog:
	* diagnostic-show-locus.c: Include "gcc-rich-location.h".
	(layout::m_primary_loc): New field.
	(layout::layout): Initialize new field.  Move location filtering
	logic from here to...
	(layout::maybe_add_location_range): ...this new method.  Add
	support for filtering to just the lines already specified by other
	locations.
	(layout::will_show_line_p): New method.
	(selftest::test_add_location_if_nearby): New test function.
	(selftest::diagnostic_show_locus_c_tests): Call it.
	* gcc-rich-location.h (gcc_rich_location::add_location_if_nearby):
	New method.

From-SVN: r250133

gcc/ChangeLog

+2017-07-11  David Malcolm  <dmalcolm@redhat.com>
+
+	* diagnostic-show-locus.c: Include "gcc-rich-location.h".
+	(layout::m_primary_loc): New field.
+	(layout::layout): Initialize new field.  Move location filtering
+	logic from here to...
+	(layout::maybe_add_location_range): ...this new method.  Add
+	support for filtering to just the lines already specified by other
+	locations.
+	(layout::will_show_line_p): New method.
+	(selftest::test_add_location_if_nearby): New test function.
+	(selftest::diagnostic_show_locus_c_tests): Call it.
+	* gcc-rich-location.h (gcc_rich_location::add_location_if_nearby):
+	New method.
+
 2017-07-11  Tom de Vries  <tom@codesourcery.com>
 
 	* config/nvptx/nvptx.c (WORKAROUND_PTXJIT_BUG): New macro.

gcc/gcc-rich-location.h

@@ -40,6 +40,27 @@ class gcc_rich_location : public rich_location
 
   void add_fixit_misspelled_id (location_t misspelled_token_loc,
 				tree hint_id);
+
+  /* If LOC is within the spans of lines that will already be printed for
+     this gcc_rich_location, then add it as a secondary location
+     and return true.
+
+     Otherwise return false.
+
+     This allows for a diagnostic to compactly print secondary locations
+     in one diagnostic when these are near enough the primary locations for
+     diagnostics-show-locus.c to cope with them, and to fall back to
+     printing them via a note otherwise e.g.:
+
+	gcc_rich_location richloc (primary_loc);
+	bool added secondary = richloc.add_location_if_nearby (secondary_loc);
+	error_at_rich_loc (&richloc, "main message");
+	if (!added secondary)
+	  inform (secondary_loc, "message for secondary");
+
+     Implemented in diagnostic-show-locus.c.  */
+
+  bool add_location_if_nearby (location_t loc);
 };
 
 #endif /* GCC_RICH_LOCATION_H */