[PATCH] c++: Member initializer list diagnostic locations [PR94024]

[Patrick Palka]

This patch preserves the source locations of each node in a member
initializer list so that during processing of the list we can set
input_location appropriately for generally more accurate diagnostic
locations.  Since TREE_LIST nodes are tcc_exceptional, they can't have
source locations, so we instead store the location in a dummy
tcc_expression node within the TREE_TYPE of the list node.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK to
commit?

gcc/cp/ChangeLog:

	PR c++/94024
	* init.c (sort_mem_initializers): Preserve TREE_TYPE of the
	member initializer list node.
	(emit_mem_initializers): Set input_location when performing each
	member initialization.
	* parser.c (cp_parser_mem_initializer_list): Attach the source
	location of this initializer to a dummy EMPTY_CLASS_EXPR within
	the TREE_TYPE of the list node.
	* pt.c (tsubst_initializer_list): Preserve TREE_TYPE of the
	member initializer list node.

gcc/testsuite/ChangeLog:

	PR c++/94024
	* g++.dg/diagnostic/mem-init1.C: New test.
---
 gcc/cp/init.c                               |  6 +++++
 gcc/cp/parser.c                             |  8 ++++++
 gcc/cp/pt.c                                 |  3 +++
 gcc/testsuite/g++.dg/diagnostic/mem-init1.C | 29 +++++++++++++++++++++
 4 files changed, 46 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/diagnostic/mem-init1.C

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index cb9bd2dbfba..3f089404cf2 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -1151,6 +1151,8 @@ sort_mem_initializers (tree t, tree mem_inits)
 
       /* Record the initialization.  */
       TREE_VALUE (subobject_init) = TREE_VALUE (init);
+      /* Carry over the dummy TREE_TYPE node containing the source location.  */
+      TREE_TYPE (subobject_init) = TREE_TYPE (init);
       next_subobject = subobject_init;
     }
 
@@ -1367,6 +1369,10 @@ emit_mem_initializers (tree mem_inits)
   /* Initialize the data members.  */
   while (mem_inits)
     {
+      /* If this initializer was explicitly provided, then the dummy TREE_TYPE
+	 node contains the source location.  */
+      iloc_sentinel ils (EXPR_LOCATION (TREE_TYPE (mem_inits)));
+
       perform_member_init (TREE_PURPOSE (mem_inits),
 			   TREE_VALUE (mem_inits));
       mem_inits = TREE_CHAIN (mem_inits);
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index ab088874ba7..2f9b8786121 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -15326,6 +15326,14 @@ cp_parser_mem_initializer_list (cp_parser* parser)
 	{
 	  TREE_CHAIN (mem_initializer) = mem_initializer_list;
 	  mem_initializer_list = mem_initializer;
+
+	  /* We can't attach the source location of this initializer directly to
+	     the list node, so we instead attach it to a dummy EMPTY_CLASS_EXPR
+	     within the TREE_TYPE of the list node.  */
+	  TREE_TYPE (mem_initializer) = build0 (EMPTY_CLASS_EXPR, NULL_TREE);
+	  SET_EXPR_LOCATION (TREE_TYPE (mem_initializer),
+			     make_location (token->location,
+					    token->location, input_location));
 	}
       /* If the next token is not a `,', we're done.  */
       if (cp_lexer_next_token_is_not (parser->lexer, CPP_COMMA))
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 3a168d506cf..bed1a3532e7 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -26014,6 +26014,9 @@ tsubst_initializer_list (tree t, tree argvec)
           if (decl)
             {
               init = build_tree_list (decl, init);
+	      /* Carry over the dummy TREE_TYPE node containing the source
+		 location.  */
+	      TREE_TYPE (init) = TREE_TYPE (t);
               TREE_CHAIN (init) = inits;
               inits = init;
             }
diff --git a/gcc/testsuite/g++.dg/diagnostic/mem-init1.C b/gcc/testsuite/g++.dg/diagnostic/mem-init1.C
new file mode 100644
index 00000000000..b749c72cd8b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/mem-init1.C
@@ -0,0 +1,29 @@
+// PR c++/94024
+// { dg-do compile }
+
+struct A {
+    A()
+    : a()       // { dg-error "reference type" }
+    , b(1)      // { dg-error "incompatible" }
+    , c(0)      // { dg-bogus "" }
+    {}
+
+    int &a;
+    int b[1];
+    char c;
+};
+
+template<typename T, typename U>
+struct B {
+    B()
+    : a()       // { dg-error "reference type" }
+    , b(1)      // { dg-error "incompatible" }
+    , c(0)      // { dg-bogus "" }
+    {}
+
+    T a;
+    U b;
+    char c;
+};
+
+B<int&, int[1]> b;
-- 
2.28.0.89.g85b4e0a6dc