[4/4] C: add fixit hint to misspelled field names

Similar to the C++ case, but more involved as the location of the
pertinent token isn't readily available.  The patch adds it as a param
to build_component_ref.  All callers are updated to provide the info,
apart from objc_build_component_ref; fixing the latter would lead to
a cascade of other changes, so it's simplest to provide UNKNOWN_LOCATION
there and have build_component_ref fall back gracefully for this case
to the old behavior of showing a hint in the message, without a fixit
replacement in the source view.

This does slightly change the location of the error; before we had:

test.c:11:13: error: 'union u' has no member named 'colour'; did you mean 'color'?
   return ptr->colour;
             ^~

with the patch we have:

test.c:11:15: error: 'union u' has no member named 'colour'; did you mean 'color'?
   return ptr->colour;
               ^~~~~~
               color

I think the location change is an improvement.

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

OK for trunk?

gcc/c/ChangeLog:
	* c-parser.c (c_parser_postfix_expression): In __builtin_offsetof
	and structure element reference, capture the location of the
	element name token and pass it to build_component_ref.
	(c_parser_postfix_expression_after_primary): Likewise for
	structure element dereference.
	(c_parser_omp_variable_list): Likewise for
	OMP_CLAUSE_{_CACHE, MAP, FROM, TO},
	* c-tree.h (build_component_ref): Add location_t param.
	* c-typeck.c (build_component_ref): Add location_t param
	COMPONENT_LOC.  Use it, if available, when issuing hints about
	mispelled member names to provide a fixit replacement hint.

gcc/objc/ChangeLog:
	* objc-act.c (objc_build_component_ref): Update call
	to build_component_ref for added param, passing UNKNOWN_LOCATION.

gcc/testsuite/ChangeLog:
	* gcc.dg/spellcheck-fields-2.c: New test case.
---
 gcc/c/c-parser.c                           | 34 +++++++++++++++++++++---------
 gcc/c/c-tree.h                             |  2 +-
 gcc/c/c-typeck.c                           | 26 +++++++++++++++++++----
 gcc/objc/objc-act.c                        |  3 ++-
 gcc/testsuite/gcc.dg/spellcheck-fields-2.c | 19 +++++++++++++++++
 5 files changed, 68 insertions(+), 16 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/spellcheck-fields-2.c

Ping:
  https://gcc.gnu.org/ml/gcc-patches/2016-04/msg01834.html


On Thu, 2016-04-28 at 10:28 -0400, David Malcolm wrote:
> Similar to the C++ case, but more involved as the location of the
> pertinent token isn't readily available.  The patch adds it as a
> param
> to build_component_ref.  All callers are updated to provide the info,
> apart from objc_build_component_ref; fixing the latter would lead to
> a cascade of other changes, so it's simplest to provide
> UNKNOWN_LOCATION
> there and have build_component_ref fall back gracefully for this case
> to the old behavior of showing a hint in the message, without a fixit
> replacement in the source view.
> 
> This does slightly change the location of the error; before we had:
> 
> test.c:11:13: error: 'union u' has no member named 'colour'; did you
> mean 'color'?
>    return ptr->colour;
>              ^~
> 
> with the patch we have:
> 
> test.c:11:15: error: 'union u' has no member named 'colour'; did you
> mean 'color'?
>    return ptr->colour;
>                ^~~~~~
>                color
> 
> I think the location change is an improvement.
> 
> Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
> 
> OK for trunk?
> 
> gcc/c/ChangeLog:
> 	* c-parser.c (c_parser_postfix_expression): In
> __builtin_offsetof
> 	and structure element reference, capture the location of the
> 	element name token and pass it to build_component_ref.
> 	(c_parser_postfix_expression_after_primary): Likewise for
> 	structure element dereference.
> 	(c_parser_omp_variable_list): Likewise for
> 	OMP_CLAUSE_{_CACHE, MAP, FROM, TO},
> 	* c-tree.h (build_component_ref): Add location_t param.
> 	* c-typeck.c (build_component_ref): Add location_t param
> 	COMPONENT_LOC.  Use it, if available, when issuing hints about
> 	mispelled member names to provide a fixit replacement hint.
> 
> gcc/objc/ChangeLog:
> 	* objc-act.c (objc_build_component_ref): Update call
> 	to build_component_ref for added param, passing
> UNKNOWN_LOCATION.
> 
> gcc/testsuite/ChangeLog:
> 	* gcc.dg/spellcheck-fields-2.c: New test case.
> ---
>  gcc/c/c-parser.c                           | 34
> +++++++++++++++++++++---------
>  gcc/c/c-tree.h                             |  2 +-
>  gcc/c/c-typeck.c                           | 26 +++++++++++++++++++-
> ---
>  gcc/objc/objc-act.c                        |  3 ++-
>  gcc/testsuite/gcc.dg/spellcheck-fields-2.c | 19 +++++++++++++++++
>  5 files changed, 68 insertions(+), 16 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/spellcheck-fields-2.c
> 
> diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
> index 36c44ab..19e6772 100644
> --- a/gcc/c/c-parser.c
> +++ b/gcc/c/c-parser.c
> @@ -7707,8 +7707,9 @@ c_parser_postfix_expression (c_parser *parser)
>  	       accept sub structure and sub array references.  */
>  	    if (c_parser_next_token_is (parser, CPP_NAME))
>  	      {
> +		c_token *comp_tok = c_parser_peek_token (parser);
>  		offsetof_ref = build_component_ref
> -		  (loc, offsetof_ref, c_parser_peek_token (parser)
> ->value);
> +		  (loc, offsetof_ref, comp_tok->value, comp_tok
> ->location);
>  		c_parser_consume_token (parser);
>  		while (c_parser_next_token_is (parser, CPP_DOT)
>  		       || c_parser_next_token_is (parser,
> @@ -7734,9 +7735,10 @@ c_parser_postfix_expression (c_parser *parser)
>  			    c_parser_error (parser, "expected
> identifier");
>  			    break;
>  			  }
> +			c_token *comp_tok = c_parser_peek_token
> (parser);
>  			offsetof_ref = build_component_ref
> -			  (loc, offsetof_ref,
> -			   c_parser_peek_token (parser)->value);
> +			  (loc, offsetof_ref, comp_tok->value,
> +			   comp_tok->location);
>  			c_parser_consume_token (parser);
>  		      }
>  		    else
> @@ -8213,7 +8215,7 @@ c_parser_postfix_expression_after_primary
> (c_parser *parser,
>  {
>    struct c_expr orig_expr;
>    tree ident, idx;
> -  location_t sizeof_arg_loc[3];
> +  location_t sizeof_arg_loc[3], comp_loc;
>    tree sizeof_arg[3];
>    unsigned int literal_zero_mask;
>    unsigned int i;
> @@ -8327,7 +8329,11 @@ c_parser_postfix_expression_after_primary
> (c_parser *parser,
>  	  c_parser_consume_token (parser);
>  	  expr = default_function_array_conversion (expr_loc, expr);
>  	  if (c_parser_next_token_is (parser, CPP_NAME))
> -	    ident = c_parser_peek_token (parser)->value;
> +	    {
> +	      c_token *comp_tok = c_parser_peek_token (parser);
> +	      ident = comp_tok->value;
> +	      comp_loc = comp_tok->location;
> +	    }
>  	  else
>  	    {
>  	      c_parser_error (parser, "expected identifier");
> @@ -8339,7 +8345,8 @@ c_parser_postfix_expression_after_primary
> (c_parser *parser,
>  	  start = expr.get_start ();
>  	  finish = c_parser_peek_token (parser)->get_finish ();
>  	  c_parser_consume_token (parser);
> -	  expr.value = build_component_ref (op_loc, expr.value,
> ident);
> +	  expr.value = build_component_ref (op_loc, expr.value,
> ident,
> +					    comp_loc);
>  	  set_c_expr_source_range (&expr, start, finish);
>  	  expr.original_code = ERROR_MARK;
>  	  if (TREE_CODE (expr.value) != COMPONENT_REF)
> @@ -8359,7 +8366,11 @@ c_parser_postfix_expression_after_primary
> (c_parser *parser,
>  	  c_parser_consume_token (parser);
>  	  expr = convert_lvalue_to_rvalue (expr_loc, expr, true,
> false);
>  	  if (c_parser_next_token_is (parser, CPP_NAME))
> -	    ident = c_parser_peek_token (parser)->value;
> +	    {
> +	      c_token *comp_tok = c_parser_peek_token (parser);
> +	      ident = comp_tok->value;
> +	      comp_loc = comp_tok->location;
> +	    }
>  	  else
>  	    {
>  	      c_parser_error (parser, "expected identifier");
> @@ -8375,7 +8386,7 @@ c_parser_postfix_expression_after_primary
> (c_parser *parser,
>  					    build_indirect_ref
> (op_loc,
>  								expr
> .value,
>  								RO_A
> RROW),
> -					    ident);
> +					    ident, comp_loc);
>  	  set_c_expr_source_range (&expr, start, finish);
>  	  expr.original_code = ERROR_MARK;
>  	  if (TREE_CODE (expr.value) != COMPONENT_REF)
> @@ -10621,9 +10632,12 @@ c_parser_omp_variable_list (c_parser
> *parser,
>  		      t = error_mark_node;
>  		      break;
>  		    }
> -		  tree ident = c_parser_peek_token (parser)->value;
> +
> +		  c_token *comp_tok = c_parser_peek_token (parser);
> +		  tree ident = comp_tok->value;
> +		  location_t comp_loc = comp_tok->location;
>  		  c_parser_consume_token (parser);
> -		  t = build_component_ref (op_loc, t, ident);
> +		  t = build_component_ref (op_loc, t, ident,
> comp_loc);
>  		}
>  	      /* FALLTHROUGH  */
>  	    case OMP_CLAUSE_DEPEND:
> diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
> index 4633182..3201a71 100644
> --- a/gcc/c/c-tree.h
> +++ b/gcc/c/c-tree.h
> @@ -604,7 +604,7 @@ extern struct c_expr convert_lvalue_to_rvalue
> (location_t, struct c_expr,
>  					       bool, bool);
>  extern void mark_exp_read (tree);
>  extern tree composite_type (tree, tree);
> -extern tree build_component_ref (location_t, tree, tree);
> +extern tree build_component_ref (location_t, tree, tree,
> location_t);
>  extern tree build_array_ref (location_t, tree, tree);
>  extern tree build_external_ref (location_t, tree, int, tree *);
>  extern void pop_maybe_used (bool);
> diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
> index 58c2139..8aece1a 100644
> --- a/gcc/c/c-typeck.c
> +++ b/gcc/c/c-typeck.c
> @@ -2309,10 +2309,12 @@ should_suggest_deref_p (tree datum_type)
>  
>  /* 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.  */
> +   location of the COMPONENT_REF.  COMPONENT_LOC is the location
> +   of COMPONENT.  */
>  
>  tree
> -build_component_ref (location_t loc, tree datum, tree component)
> +build_component_ref (location_t loc, tree datum, tree component,
> +		     location_t component_loc)
>  {
>    tree type = TREE_TYPE (datum);
>    enum tree_code code = TREE_CODE (type);
> @@ -2344,8 +2346,24 @@ build_component_ref (location_t loc, tree
> datum, tree component)
>  	{
>  	  tree guessed_id = lookup_field_fuzzy (type, component);
>  	  if (guessed_id)
> -	    error_at (loc, "%qT has no member named %qE; did you
> mean %qE?",
> -		      type, component, guessed_id);
> +	    {
> +	      /* Attempt to provide a fixit replacement hint, if
> +		 we have a valid range for the component.  */
> +	      location_t reported_loc
> +		= (component_loc != UNKNOWN_LOCATION) ?
> component_loc : loc;
> +	      rich_location rich_loc (line_table, reported_loc);
> +	      if (component_loc != UNKNOWN_LOCATION)
> +		{
> +		  source_range component_range =
> +		    get_range_from_loc (line_table, component_loc);
> +		  rich_loc.add_fixit_replace (component_range,
> +					      IDENTIFIER_POINTER
> (guessed_id));
> +		}
> +	      error_at_rich_loc
> +		(&rich_loc,
> +		 "%qT has no member named %qE; did you mean %qE?",
> +		 type, component, guessed_id);
> +	    }
>  	  else
>  	    error_at (loc, "%qT has no member named %qE", type,
> component);
>  	  return error_mark_node;
> diff --git a/gcc/objc/objc-act.c b/gcc/objc/objc-act.c
> index 4856457..44f01d2 100644
> --- a/gcc/objc/objc-act.c
> +++ b/gcc/objc/objc-act.c
> @@ -2654,7 +2654,8 @@ objc_build_component_ref (tree datum, tree
> component)
>    return finish_class_member_access_expr (datum, component, false,
>                                            tf_warning_or_error);
>  #else
> -  return build_component_ref (input_location, datum, component);
> +  return build_component_ref (input_location, datum, component,
> +			      UNKNOWN_LOCATION);
>  #endif
>  }
>  
> diff --git a/gcc/testsuite/gcc.dg/spellcheck-fields-2.c
> b/gcc/testsuite/gcc.dg/spellcheck-fields-2.c
> new file mode 100644
> index 0000000..d6ebff1
> --- /dev/null
> +++ b/gcc/testsuite/gcc.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 "" } */

On Tue, 31 May 2016, David Malcolm wrote:

> Ping:
>   https://gcc.gnu.org/ml/gcc-patches/2016-04/msg01834.html

OK.  What about field names in designated initializers (both C99-style and 
old-style)?