[PATCH] C: fixits for modernizing structure member designators

[David Malcolm]

This patch adds fix-it hints to our warning for old-style structure
member designators, showing how to modernize them to C99 form.

For example:

modernize-named-inits.c:19:5: warning: obsolete use of designated initializer 
with ‘:’ [-Wpedantic]
  foo: 1,
     ^
  .  =

In conjunction with the not-yet-in-trunk -fdiagnostics-generate-patch,
this can generate patches like this:

--- modernize-named-inits.c
+++ modernize-named-inits.c
@@ -16,7 +16,7 @@
 /* Old-style named initializers.  */
 
 struct foo old_style_f = {
- foo: 1,
- bar: 2,
+ .foo= 1,
+ .bar= 2,
 };

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

OK for trunk?

gcc/c/ChangeLog:
        * c-parser.c (c_parser_initelt): Provide fix-it hints for
        modernizing old-style structure member designator to C99 style.

gcc/testsuite/ChangeLog:
        * gcc.dg/modernize-named-inits.c: New test case.
---
 gcc/c/c-parser.c                             | 17 +++++++-----
 gcc/testsuite/gcc.dg/modernize-named-inits.c | 39 ++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/modernize-named-inits.c

diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index c245e70..a6281fc 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -4459,13 +4459,18 @@ c_parser_initelt (c_parser *parser, struct obstack * 
braced_init_obstack)
       && c_parser_peek_2nd_token (parser)->type == CPP_COLON)
     {
       /* Old-style structure member designator.  */
-      set_init_label (c_parser_peek_token (parser)->location,
-                     c_parser_peek_token (parser)->value,
-                     c_parser_peek_token (parser)->location,
-                     braced_init_obstack);
+      location_t name_loc = c_parser_peek_token (parser)->location;
+      tree fieldname = c_parser_peek_token (parser)->value;
+      location_t colon_loc = c_parser_peek_2nd_token (parser)->location;
+      set_init_label (name_loc, fieldname, name_loc, braced_init_obstack);
       /* Use the colon as the error location.  */
-      pedwarn (c_parser_peek_2nd_token (parser)->location, OPT_Wpedantic,
-              "obsolete use of designated initializer with %<:%>");
+      rich_location richloc (line_table, colon_loc);
+      /* Provide fix-it hints for converting to C99 style i.e.
+        from "NAME:" to ".NAME =".  */
+      richloc.add_fixit_insert (name_loc, ".");
+      richloc.add_fixit_replace (colon_loc, "=");
+      pedwarn_at_rich_loc (&richloc, OPT_Wpedantic,
+                          "obsolete use of designated initializer with %<:%>");
       c_parser_consume_token (parser);
       c_parser_consume_token (parser);
     }
diff --git a/gcc/testsuite/gcc.dg/modernize-named-inits.c 
b/gcc/testsuite/gcc.dg/modernize-named-inits.c
new file mode 100644
index 0000000..4e16494
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/modernize-named-inits.c
@@ -0,0 +1,39 @@
+/* { dg-do compile } */
+/* { dg-options "-fdiagnostics-show-caret -std=c99 -pedantic" } */
+
+struct foo
+{
+  int foo;
+  int bar;
+};
+
+union u
+{
+  int color;
+  int shape;
+};
+
+/* Old-style named initializers.  */
+
+struct foo old_style_f = {
+ foo: 1, /* { dg-warning "5: obsolete use of designated initializer with ':'" 
} */
+/* { dg-begin-multiline-output "" }
+  foo: 1,
+     ^
+  .  =
+   { dg-end-multiline-output "" } */
+
+ bar    : 1, /* { dg-warning "9: obsolete use of designated initializer with 
':'" } */
+ /* { dg-begin-multiline-output "" }
+  bar    : 1,
+         ^
+  .      =
+    { dg-end-multiline-output "" } */
+};
+
+union u old_style_u = { color: 3 }; /* { dg-warning "30: obsolete use of 
designated initializer with ':'" } */
+/* { dg-begin-multiline-output "" }
+ union u old_style_u = { color: 3 };
+                              ^
+                         .    =
+   { dg-end-multiline-output "" } */
-- 
1.8.5.3