From 5ce9a9e55c8deba4a2d4da4401debf1302a4631e Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Tue, 2 Apr 2024 19:46:18 +0100
Subject: [PATCH] Improve error for duplicate declaration due to homograph.
 Fixes #875

---
 src/names.c             | 12 +++++++++++-
 test/parse/issue875.vhd | 19 +++++++++++++++++++
 test/test_parse.c       | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 test/parse/issue875.vhd

diff --git a/src/names.c b/src/names.c
index 4e99b053..8619577b 100644
--- a/src/names.c
+++ b/src/names.c
@@ -862,7 +862,17 @@ static symbol_t *make_visible(scope_t *s, ident_t name, tree_t decl,
          }
          else if (dd->origin == origin && !type_is_none(type)) {
             diag_t *d = diag_new(DIAG_ERROR, tree_loc(decl));
-            diag_printf(d, "%s already declared in this region", type_pp(type));
+            if (type_strict_eq(tree_type(dd->tree), type))
+               diag_printf(d, "%s already declared in this region",
+                           type_pp(type));
+            else {
+               diag_printf(d, "homograph of %s already declared in this region",
+                           type_pp(type));
+               diag_hint(d, NULL, "only the base type is considered when "
+                         "determining if two overloads have the same parameter "
+                         "type profile");
+            }
+
             diag_hint(d, tree_loc(dd->tree), "previous declaration was here");
             diag_hint(d, tree_loc(decl), "duplicate declaration");
             diag_emit(d);
diff --git a/test/parse/issue875.vhd b/test/parse/issue875.vhd
new file mode 100644
index 00000000..75ba0d33
--- /dev/null
+++ b/test/parse/issue875.vhd
@@ -0,0 +1,19 @@
+package repro is
+  subtype instruction32_t is bit_vector(31 downto 0);
+  subtype opcode32_t is bit_vector(6 downto 0);
+
+  function has_rd(op  : opcode32_t) return boolean;
+  function has_rd(ins : instruction32_t) return boolean;
+end;
+
+package body repro is
+  function has_rd(op : opcode32_t) return boolean is
+  begin
+    return false;
+  end function;
+
+  function has_rd(ins : instruction32_t) return boolean is
+  begin
+    return true;
+  end function;
+end package body;
diff --git a/test/test_parse.c b/test/test_parse.c
index 9eab3182..56d9c3e9 100644
--- a/test/test_parse.c
+++ b/test/test_parse.c
@@ -6254,6 +6254,38 @@ START_TEST(test_aggregate)
 }
 END_TEST
 
+START_TEST(test_issue875)
+{
+   input_from_file(TESTDIR "/parse/issue875.vhd");
+
+   const error_t expect[] = {
+      {  6, "homograph of HAS_RD [INSTRUCTION32_T return BOOLEAN] already "
+         "declared in this region" },
+      {  0, "duplicate declaration" },
+      {  0, "only the base type is considered when determining" },
+      {  0, "previous declaration was here" },
+      {  9, "design unit depends on WORK.REPRO which was analysed "
+         "with errors" },
+      { -1, NULL }
+   };
+   expect_errors(expect);
+
+   tree_t p = parse();
+   fail_if(p == NULL);
+   fail_unless(tree_kind(p) == T_PACKAGE);
+   lib_put_error(lib_work(), p);
+
+   tree_t b = parse();
+   fail_if(b == NULL);
+   fail_unless(tree_kind(b) == T_PACK_BODY);
+   lib_put(lib_work(), b);
+
+   fail_unless(parse() == NULL);
+
+   check_expected_errors();
+}
+END_TEST
+
 Suite *get_parse_tests(void)
 {
    Suite *s = suite_create("parse");
@@ -6393,6 +6425,7 @@ Suite *get_parse_tests(void)
    tcase_add_test(tc_core, test_issue848);
    tcase_add_test(tc_core, test_issue870);
    tcase_add_test(tc_core, test_aggregate);
+   tcase_add_test(tc_core, test_issue875);
    suite_add_tcase(s, tc_core);
 
    return s;
-- 
2.39.2