PR 62314: add ability to add fixit-hints to a diagnostic

This is the combination of two patches:
  [PATCH 01/02] PR/62314: add ability to add fixit-hints
  [PATCH 02/02] C FE: add fix-it hint for . vs ->

gcc/ChangeLog:
	PR 62314
	* diagnostic-show-locus.c (colorizer::set_fixit_hint): New.
	(class layout): Update comment
	(layout::print_any_fixits): New method.
	(layout::move_to_column): New method.
	(diagnostic_show_locus): Add call to layout.print_any_fixits.

gcc/c/ChangeLog:
	PR 62314
	* c-typeck.c (should_suggest_deref_p): New function.
	(build_component_ref): Special-case POINTER_TYPE when
	generating a "not a structure of union"  error message, and
	suggest a "->" rather than a ".", providing a fix-it hint.

gcc/testsuite/ChangeLog:
	PR 62314
	* gcc.dg/fixits.c: New file.
	* gcc.dg/plugin/diagnostic-test-show-locus-ascii-bw.c
	(test_fixit_insert): New.
	(test_fixit_remove): New.
	(test_fixit_replace): New.
	* gcc.dg/plugin/diagnostic-test-show-locus-ascii-color.c
	(test_fixit_insert): New.
	(test_fixit_remove): New.
	(test_fixit_replace): New.
	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
	(test_show_locus): Add tests of rendering fixit hints.

libcpp/ChangeLog:
	PR 62314
	* include/line-map.h (source_range::intersects_line_p): New
	method.
	(rich_location::~rich_location): New.
	(rich_location::add_fixit_insert): New method.
	(rich_location::add_fixit_remove): New method.
	(rich_location::add_fixit_replace): New method.
	(rich_location::get_num_fixit_hints): New accessor.
	(rich_location::get_fixit_hint): New accessor.
	(rich_location::MAX_FIXIT_HINTS): New constant.
	(rich_location::m_num_fixit_hints): New field.
	(rich_location::m_fixit_hints): New field.
	(class fixit_hint): New class.
	(class fixit_insert): New class.
	(class fixit_remove): New class.
	(class fixit_replace): New class.
	* line-map.c (source_range::intersects_line_p): New method.
	(rich_location::rich_location): Add initialization of
	m_num_fixit_hints to both ctors.
	(rich_location::~rich_location): New.
	(rich_location::add_fixit_insert): New method.
	(rich_location::add_fixit_remove): New method.
	(rich_location::add_fixit_replace): New method.
	(fixit_insert::fixit_insert): New.
	(fixit_insert::~fixit_insert): New.
	(fixit_insert::affects_line_p): New.
	(fixit_remove::fixit_remove): New.
	(fixit_remove::affects_line_p): New.
	(fixit_replace::fixit_replace): New.
	(fixit_replace::~fixit_replace): New.
	(fixit_replace::affects_line_p): New.

From-SVN: r230674

2 files changed, 47 insertions, 0 deletions

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 9399053..96c5823 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,11 @@
+2015-11-20  David Malcolm  <dmalcolm@redhat.com>
+
+	PR 62314
+	* c-typeck.c (should_suggest_deref_p): New function.
+	(build_component_ref): Special-case POINTER_TYPE when
+	generating a "not a structure of union"  error message, and
+	suggest a "->" rather than a ".", providing a fix-it hint.
+
 2015-11-19  David Malcolm  <dmalcolm@redhat.com>
 
 	* c-typeck.c (lookup_field_fuzzy): Move determination of closest
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 9284bfc..741c75c 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -2277,6 +2277,33 @@ lookup_field_fuzzy (tree type, tree component)
   return find_closest_identifier (component, &candidates);
 }
 
+/* Support function for build_component_ref's error-handling.
+
+   Given DATUM_TYPE, and "DATUM.COMPONENT", where DATUM is *not* a
+   struct or union, should we suggest "DATUM->COMPONENT" as a hint?  */
+
+static bool
+should_suggest_deref_p (tree datum_type)
+{
+  /* We don't do it for Objective-C, since Objective-C 2.0 dot-syntax
+     allows "." for ptrs; we could be handling a failed attempt
+     to access a property.  */
+  if (c_dialect_objc ())
+    return false;
+
+  /* Only suggest it for pointers...  */
+  if (TREE_CODE (datum_type) != POINTER_TYPE)
+    return false;
+
+  /* ...to structs/unions.  */
+  tree underlying_type = TREE_TYPE (datum_type);
+  enum tree_code code = TREE_CODE (underlying_type);
+  if (code == RECORD_TYPE || code == UNION_TYPE)
+    return true;
+  else
+    return false;
+}
+
 /* Make an expression to refer to the COMPONENT field of structure or
    union value DATUM.  COMPONENT is an IDENTIFIER_NODE.  LOC is the
    location of the COMPONENT_REF.  */
@@ -2369,6 +2396,18 @@ build_component_ref (location_t loc, tree datum, tree component)
 
       return ref;
     }
+  else if (should_suggest_deref_p (type))
+    {
+      /* Special-case the error message for "ptr.field" for the case
+	 where the user has confused "." vs "->".  */
+      rich_location richloc (line_table, loc);
+      /* "loc" should be the "." token.  */
+      richloc.add_fixit_replace (source_range::from_location (loc), "->");
+      error_at_rich_loc (&richloc,
+			 "%qE is a pointer; did you mean to use %<->%>?",
+			 datum);
+      return error_mark_node;
+    }
   else if (code != ERROR_MARK)
     error_at (loc,
 	      "request for member %qE in something not a structure or union",