C/C++: add fix-it hints for various missing symbols

The patch improves our C/C++ frontends' handling of missing
symbols, by making c_parser_require and cp_parser_require use
"better" locations for the diagnostic, and insert fix-it hints,
under certain circumstances (see the comments in the patch for
full details).

For example, for this code with a missing semicolon:

  $ cat test.c
  int missing_semicolon (void)
  {
    return 42
  }

  trunk currently emits:

  test.c:4:1: error: expected ';' before '}' token
   }
   ^

This patch adds a fix-it hint for the missing semicolon, and puts
the error at the location of the missing semicolon, printing the
followup token as a secondary location:

  test.c:3:12: error: expected ';' before '}' token
     return 42
              ^
              ;
   }
   ~

More examples can be seen in the test cases.

gcc/c-family/ChangeLog:
	* c-common.c (enum missing_token_insertion_kind): New enum.
	(get_missing_token_insertion_kind): New function.
	(maybe_suggest_missing_token_insertion): New function.
	* c-common.h (maybe_suggest_missing_token_insertion): New decl.

gcc/c/ChangeLog:
	* c-parser.c (c_parser_require): Add "type_is_unique" param and
	use it to guard calls to maybe_suggest_missing_token_insertion.
	(c_parser_parms_list_declarator): Override default value of new
	"type_is_unique" param to c_parser_require.
	(c_parser_asm_statement): Likewise.
	* c-parser.h (c_parser_require): Add "type_is_unique" param,
	defaulting to true.

gcc/cp/ChangeLog:
	* parser.c (get_required_cpp_ttype): New function.
	(cp_parser_error_1): Call it, using the result to call
	maybe_suggest_missing_token_insertion.

gcc/testsuite/ChangeLog:
	* c-c++-common/cilk-plus/AN/parser_errors.c: Update expected
	output to reflect changes to reported locations of missing
	symbols.
	* c-c++-common/cilk-plus/AN/parser_errors2.c: Likewise.
	* c-c++-common/cilk-plus/AN/parser_errors3.c: Likewise.
	* c-c++-common/cilk-plus/AN/pr61191.c: Likewise.
	* c-c++-common/gomp/pr63326.c: Likewise.
	* c-c++-common/missing-close-symbol.c: Likewise, also update for
	new fix-it hints.
	* c-c++-common/missing-symbol.c: Likewise, also add test coverage
	for missing colon in ternary operator.
	* g++.dg/cpp1y/digit-sep-neg.C: Likewise.
	* g++.dg/cpp1y/pr65202.C: Likewise.
	* g++.dg/missing-symbol-2.C: New test case.
	* g++.dg/other/do1.C: Update expected output to reflect
	changes to reported locations of missing symbols.
	* g++.dg/parse/error11.C: Likewise.
	* g++.dg/template/error11.C: Likewise.
	* gcc.dg/missing-symbol-2.c: New test case.
	* gcc.dg/missing-symbol-3.c: New test case.
	* gcc.dg/noncompile/940112-1.c: Update expected output to reflect
	changes to reported locations of missing symbols.
	* gcc.dg/noncompile/971104-1.c: Likewise.
	* obj-c++.dg/exceptions-6.mm: Likewise.
	* obj-c++.dg/pr48187.mm: Likewise.
	* objc.dg/exceptions-6.m: Likewise.

From-SVN: r253690

4 files changed, 125 insertions, 4 deletions

diff --git a/gcc/testsuite/gcc.dg/missing-symbol-2.c b/gcc/testsuite/gcc.dg/missing-symbol-2.c
new file mode 100644
index 0000000..7ee795d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/missing-symbol-2.c
@@ -0,0 +1,71 @@
+/* { dg-options "-fdiagnostics-show-caret -Wno-switch-unreachable" } */
+
+extern int foo (void);
+
+void missing_open_paren (void)
+{
+  if foo ()) /* { dg-line missing_open_paren } */
+    {
+    }
+  /* { dg-error "expected '\\(' before 'foo'" "" { target c } missing_open_paren } */
+  /* { dg-begin-multiline-output "" }
+   if foo ())
+      ^~~
+      (
+     { dg-end-multiline-output "" } */
+  /* { dg-error "expected statement before '\\)' token"  "" { target c } missing_open_paren } */
+  /* { dg-begin-multiline-output "" }
+   if foo ())
+            ^
+     { dg-end-multiline-output "" } */
+}
+
+void missing_close_square (void)
+{
+  const char test [42;  /* { dg-error "22: expected ']' before ';' token" } */
+  /* { dg-begin-multiline-output "" }
+   const char test [42;
+                      ^
+                      ]
+     { dg-end-multiline-output "" } */
+}
+
+int missing_semicolon (void)
+{
+  return 42 /* { dg-error "expected ';'" } */
+}
+/* { dg-begin-multiline-output "" }
+   return 42
+            ^
+            ;
+ }
+ ~           
+   { dg-end-multiline-output "" } */
+
+
+/* We don't offer a fix-it hint for this case in C, as it could be
+   colon or ellipsis.
+   TODO: we could be smarter about error-recovery here; given the
+   return perhaps we could assume a missing colon.  */
+
+int missing_colon_in_switch (int val)
+{
+  switch (val)
+    {
+    case 42
+      return 42; /* { dg-error "expected ':' or '...' before 'return'" } */
+    /* { dg-begin-multiline-output "" }
+       return 42;
+       ^~~~~~
+       { dg-end-multiline-output "" } */
+
+    default:
+      return val;
+    }
+}
+
+/* { dg-begin-multiline-output "" }
+ int dummy;
+ ^~~
+   { dg-end-multiline-output "" } */
+int dummy;/* { dg-error "expected declaration or statement at end of input" "" { target c } } */
diff --git a/gcc/testsuite/gcc.dg/missing-symbol-3.c b/gcc/testsuite/gcc.dg/missing-symbol-3.c
new file mode 100644
index 0000000..e2d00df
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/missing-symbol-3.c
@@ -0,0 +1,50 @@
+/* { dg-options "-fdiagnostics-show-caret" } */
+
+/* A sequence of bogus _Static_assert.
+   We can offer fix-it hints for some of these, but not all.  */
+
+void test_static_assert_1 (void)
+{
+  _Static_assert sizeof(int) >= sizeof(char); /* { dg-error "expected '\\(' before 'sizeof'" } */
+  /* { dg-begin-multiline-output "" }
+   _Static_assert sizeof(int) >= sizeof(char);
+                  ^~~~~~
+                  (
+     { dg-end-multiline-output "" } */
+}
+
+void test_static_assert_2 (void)
+{
+  _Static_assert(sizeof(int) >= sizeof(char); /* { dg-error "expected ',' before ';' token" } */
+  /* { dg-begin-multiline-output "" }
+   _Static_assert(sizeof(int) >= sizeof(char);
+                                             ^
+                                             ,
+     { dg-end-multiline-output "" } */
+}
+
+void test_static_assert_3 (void)
+{
+  _Static_assert(sizeof(int) >= sizeof(char),; /* { dg-error "expected string literal before ';' token" } */
+  /* { dg-begin-multiline-output "" }
+   _Static_assert(sizeof(int) >= sizeof(char),;
+                                              ^
+     { dg-end-multiline-output "" } */
+}
+
+void test_static_assert_4 (void)
+{
+  _Static_assert(sizeof(int) >= sizeof(char), "msg"; /* { dg-error "expected '\\)' before ';' token" } */
+  /* { dg-begin-multiline-output "" }
+   _Static_assert(sizeof(int) >= sizeof(char), "msg";
+                 ~                                  ^
+                                                    )
+     { dg-end-multiline-output "" } */
+}
+
+/* The final one is correct.  */
+
+void test_static_assert_5 (void)
+{
+  _Static_assert(sizeof(int) >= sizeof(char), "msg");
+}
diff --git a/gcc/testsuite/gcc.dg/noncompile/940112-1.c b/gcc/testsuite/gcc.dg/noncompile/940112-1.c
index bb5e0f6..0a9e07d 100644
--- a/gcc/testsuite/gcc.dg/noncompile/940112-1.c
+++ b/gcc/testsuite/gcc.dg/noncompile/940112-1.c
@@ -3,5 +3,5 @@ f (int x)
 {
   double e = 1;
   e = 1;
-  return (e)
-}	/* { dg-error "parse error|syntax error|expected" } */
+  return (e) /* { dg-error "parse error|syntax error|expected" } */
+}	
diff --git a/gcc/testsuite/gcc.dg/noncompile/971104-1.c b/gcc/testsuite/gcc.dg/noncompile/971104-1.c
index 39e00c6..4a04dad 100644
--- a/gcc/testsuite/gcc.dg/noncompile/971104-1.c
+++ b/gcc/testsuite/gcc.dg/noncompile/971104-1.c
@@ -27,6 +27,6 @@ static void up(int sem){
     printf("%s had processes sleeping on it!\n",
     ({ "MUTEX     ", "BARB_SEM 1", "BARB_SEM 2", "CUST_SEM 1",
        "CUST_SEM 2", "WAIT_SEM 1", "WAIT_SEM 2", "WAIT_SEM 3",
-       "WAIT_SEM 4"}	 /* { dg-error "parse error|syntax error|expected" } */
-	[( sb.sem_num )]) ); /* { dg-error "expected" } */
+       "WAIT_SEM 4"}	 /* { dg-error "expected" } */
+	[( sb.sem_num )]) );
 }