[PATCH 3/4] PR c++/62314: C++: add fixit hint to misspelled member names

[David Malcolm <dmalcolm at redhat dot com>]

When we emit a hint about a misspelled member name, it will slightly
aid readability if we use a fixit-hint to show the proposed
name in context within the source code (and in the future this
might support some kind of auto-apply in an IDE).

This patch adds such a hint to the C++ frontend, taking us from:

test.cc:10:15: error: 'struct foo' has no member named 'colour'; did you mean 'color'?
   return ptr->colour;
               ^~~~~~

to:

test.cc:10:15: error: 'struct foo' has no member named 'colour'; did you mean 'color'?
   return ptr->colour;
               ^~~~~~
               color

Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.

OK for trunk?

gcc/cp/ChangeLog:
	PR c++/62314
	* typeck.c (finish_class_member_access_expr): When
	giving a hint about a possibly-misspelled member name,
	add a fix-it replacement hint.

gcc/testsuite/ChangeLog:
	PR c++/62314
	* g++.dg/spellcheck-fields-2.C: New test case.
---
 gcc/cp/typeck.c                            | 18 +++++++++++++++---
 gcc/testsuite/g++.dg/spellcheck-fields-2.C | 19 +++++++++++++++++++
 2 files changed, 34 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/spellcheck-fields-2.C

diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 7e12009..95c777d 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -2817,9 +2817,21 @@ finish_class_member_access_expr (cp_expr object, tree name, bool template_p,
 		  tree guessed_id = lookup_member_fuzzy (access_path, name,
 							 /*want_type=*/false);
 		  if (guessed_id)
-		    error ("%q#T has no member named %qE; did you mean %qE?",
-			   TREE_CODE (access_path) == TREE_BINFO
-			   ? TREE_TYPE (access_path) : object_type, name, guessed_id);
+		    {
+		      location_t bogus_component_loc = input_location;
+		      rich_location rich_loc (line_table, bogus_component_loc);
+		      source_range bogus_component_range =
+			get_range_from_loc (line_table, bogus_component_loc);
+		      rich_loc.add_fixit_replace
+			(bogus_component_range,
+			 IDENTIFIER_POINTER (guessed_id));
+		      error_at_rich_loc
+			(&rich_loc,
+			 "%q#T has no member named %qE; did you mean %qE?",
+			 TREE_CODE (access_path) == TREE_BINFO
+			 ? TREE_TYPE (access_path) : object_type, name,
+			 guessed_id);
+		    }
 		  else
 		    error ("%q#T has no member named %qE",
 			   TREE_CODE (access_path) == TREE_BINFO
diff --git a/gcc/testsuite/g++.dg/spellcheck-fields-2.C b/gcc/testsuite/g++.dg/spellcheck-fields-2.C
new file mode 100644
index 0000000..eb10b44
--- /dev/null
+++ b/gcc/testsuite/g++.dg/spellcheck-fields-2.C
@@ -0,0 +1,19 @@
+// { dg-options "-fdiagnostics-show-caret" }
+
+union u
+{
+  int color;
+  int shape;
+};
+
+int test (union u *ptr)
+{
+  return ptr->colour; // { dg-error "did you mean .color.?" }
+}
+
+// Verify that we get an underline and a fixit hint.
+/* { dg-begin-multiline-output "" }
+   return ptr->colour;
+               ^~~~~~
+               color
+   { dg-end-multiline-output "" } */
-- 
1.8.5.3