C++ FE: offer suggestions for misspelled field names

gcc/c/ChangeLog:
	* c-typeck.c (lookup_field_fuzzy): Move determination of closest
	candidate into a new function, find_closest_identifier.

gcc/cp/ChangeLog:
	* cp-tree.h (lookup_member_fuzzy): New decl.
	* search.c: Include spellcheck.h.
	(class lookup_field_fuzzy_info): New class.
	(lookup_field_fuzzy_info::fuzzy_lookup_fnfields): New.
	(lookup_field_fuzzy_info::fuzzy_lookup_field): New.
	(lookup_field_fuzzy_r): New.
	(lookup_member_fuzzy): New.
	* typeck.c (finish_class_member_access_expr): When issuing
	a "has no member named" error, call lookup_member_fuzzy, and
	offer any result as a suggestion.

gcc/ChangeLog:
	* spellcheck-tree.c (find_closest_identifier): New function, taken
	from c/c-typeck.c:lookup_field_fuzzy, with NULL corrected to
	NULL_TREE in two places.
	* spellcheck.h (find_closest_identifier): New decl.

gcc/testsuite/ChangeLog:
	* g++.dg/spellcheck-fields.C: New file.

From-SVN: r230638

1 files changed, 41 insertions, 0 deletions

diff --git a/gcc/spellcheck-tree.c b/gcc/spellcheck-tree.c
index d203776..f7fbcc0 100644
--- a/gcc/spellcheck-tree.c
+++ b/gcc/spellcheck-tree.c
@@ -37,3 +37,44 @@ levenshtein_distance (tree ident_s, tree ident_t)
 			       IDENTIFIER_POINTER (ident_t),
 			       IDENTIFIER_LENGTH (ident_t));
 }
+
+/* Given TARGET, an identifier, and CANDIDATES, a vec of identifiers,
+   determine which element within CANDIDATES has the lowest edit
+   distance to TARGET.  If there are multiple elements with the
+   same minimal distance, the first in the vector wins.
+
+   If more than half of the letters were misspelled, the suggestion is
+   likely to be meaningless, so return NULL_TREE for this case.  */
+
+tree
+find_closest_identifier (tree target, const auto_vec<tree> *candidates)
+{
+  gcc_assert (TREE_CODE (target) == IDENTIFIER_NODE);
+
+  int i;
+  tree identifier;
+  tree best_identifier = NULL_TREE;
+  edit_distance_t best_distance = MAX_EDIT_DISTANCE;
+  FOR_EACH_VEC_ELT (*candidates, i, identifier)
+    {
+      gcc_assert (TREE_CODE (identifier) == IDENTIFIER_NODE);
+      edit_distance_t dist = levenshtein_distance (target, identifier);
+      if (dist < best_distance)
+	{
+	  best_distance = dist;
+	  best_identifier = identifier;
+	}
+    }
+
+  /* If more than half of the letters were misspelled, the suggestion is
+     likely to be meaningless.  */
+  if (best_identifier)
+    {
+      unsigned int cutoff = MAX (IDENTIFIER_LENGTH (target),
+				 IDENTIFIER_LENGTH (best_identifier)) / 2;
+      if (best_distance > cutoff)
+	return NULL_TREE;
+    }
+
+  return best_identifier;
+}