[PATCH] C: fix reported range of invalid unary dereference.

[David Malcolm]

Currently, trunk emits this for a bad unary * in C:

bad-dereference.c:10:10: error: invalid type argument of unary ‘*’ (have ‘int’)
   return *some_f.x;
          ^

The following patch fixes the reported location to highlight the
expression that was attempted to be dereferenced:

bad-dereference.c:10:10: error: invalid type argument of unary ‘*’ (have ‘int’)
   return *some_f.x;
          ^~~~~~~~~

Based on another example from:
  http://clang.llvm.org/diagnostics.html
albeit within the "Precision in Wording" example; I didn't change the
wording.

Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu.
OK for trunk in stage 3?

gcc/c/ChangeLog:
        * c-parser.c (c_parser_unary_expression): For dereferences, build
        a combined location before calling build_indirect_ref, so that
        error reports cover the full range, manually updating the c_expr
        src_range.

gcc/testsuite/ChangeLog:
        * gcc.dg/bad-dereference.c: New test case.
---
 gcc/c/c-parser.c                       |  8 ++++++--
 gcc/testsuite/gcc.dg/bad-dereference.c | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/bad-dereference.c

diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 774354a..a22c3d2 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -6691,8 +6691,12 @@ c_parser_unary_expression (c_parser *parser)
       op = c_parser_cast_expression (parser, NULL);
       finish = op.get_finish ();
       op = convert_lvalue_to_rvalue (exp_loc, op, true, true);
-      ret.value = build_indirect_ref (op_loc, op.value, RO_UNARY_STAR);
-      set_c_expr_source_range (&ret, op_loc, finish);
+      {
+       location_t combined_loc = make_location (op_loc, op_loc, finish);
+       ret.value = build_indirect_ref (combined_loc, op.value, RO_UNARY_STAR);
+       ret.src_range.m_start = op_loc;
+       ret.src_range.m_finish = finish;
+      }
       return ret;
     case CPP_PLUS:
       if (!c_dialect_objc () && !in_system_header_at (input_location))
diff --git a/gcc/testsuite/gcc.dg/bad-dereference.c 
b/gcc/testsuite/gcc.dg/bad-dereference.c
new file mode 100644
index 0000000..5f8188d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/bad-dereference.c
@@ -0,0 +1,24 @@
+/* { dg-options "-fdiagnostics-show-caret" } */
+
+struct foo
+{
+  int x;
+};
+
+int test_1 (struct foo some_f)
+{
+  return *some_f.x; /* { dg-error "invalid type argument of unary ... .have 
.int.." } */
+/* { dg-begin-multiline-output "" }
+   return *some_f.x;
+          ^~~~~~~~~
+   { dg-end-multiline-output "" } */
+}
+
+int test_2 (struct foo some_f)
+{
+  return *some_f; /* { dg-error "invalid type argument of unary ... .have 
.struct foo.." } */
+/* { dg-begin-multiline-output "" }
+   return *some_f;
+          ^~~~~~~
+   { dg-end-multiline-output "" } */
+}
-- 
1.8.5.3