[gcc/devel/c++-coroutines] c++: Diagnose a deduction guide in a wrong scope [PR91759]

[gcc/devel/c++-coroutines] c++: Diagnose a deduction guide in a wrong scope [PR91759]

[Iain D Sandoe]

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https://gcc.gnu.org/g:af8656be8df68ac26840f7844430fd595255ebd2

commit af8656be8df68ac26840f7844430fd595255ebd2
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Mar 18 08:53:23 2020 +0100

    c++: Diagnose a deduction guide in a wrong scope [PR91759]
    
    The following testcase is accepts-invalid since r7-6608-ga56c0ac08242269b.
    Before that change we had this
    "deduction guide %qD must be declared in the same scope as %qT"
    diagnostics for it, after the change it is expected to be diagnosed
    in set_decl_namespace at the not_found: label in there.  On this testcase
    nothing is diagnosed though, because set_decl_namespace isn't called at all,
    as in_namespace is NULL.
    
    The following patch restores the old warning but does it only in case we
    don't call set_decl_namespace.
    
    2020-03-18  Jakub Jelinek  <jakub@redhat.com>
    
            PR c++/91759
            * decl.c (grokfndecl): Restore old diagnostics about deduction
            guide declared in different scope if in_namespace is NULL_TREE.
    
            * g++.dg/cpp1z/class-deduction72.C: New test.

Diff:
---
 gcc/cp/ChangeLog                               |  6 ++++++
 gcc/cp/decl.c                                  |  9 +++++++++
 gcc/testsuite/ChangeLog                        |  5 +++++
 gcc/testsuite/g++.dg/cpp1z/class-deduction72.C | 11 +++++++++++
 4 files changed, 31 insertions(+)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 1db1e090e51..9aaa81a17bb 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2020-03-18  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/91759
+	* decl.c (grokfndecl): Restore old diagnostics about deduction
+	guide declared in different scope if in_namespace is NULL_TREE.
+
 2020-03-17  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/90995
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index d240436d84a..319b7ee5c1c 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -9644,6 +9644,15 @@ grokfndecl (tree ctype,
 		    "namespace scope", decl);
 	  return NULL_TREE;
 	}
+      tree type = TREE_TYPE (DECL_NAME (decl));
+      if (in_namespace == NULL_TREE
+	  && CP_DECL_CONTEXT (decl) != CP_TYPE_CONTEXT (type))
+	{
+	  error_at (location, "deduction guide %qD must be declared in the "
+			      "same scope as %qT", decl, type);
+	  inform (location_of (type), "  declared here");
+	  return NULL_TREE;
+	}
       if (funcdef_flag)
 	error_at (location,
 		  "deduction guide %qD must not have a function body", decl);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 775837d840f..8efb773437b 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-03-18  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/91759
+	* g++.dg/cpp1z/class-deduction72.C: New test.
+
 2020-03-17  Uroš Bizjak  <ubizjak@gmail.com>
 
 	* g++.dg/debug/dwarf2/const2b.C (dg-do): Fix target selector.
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction72.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction72.C
new file mode 100644
index 00000000000..60c559907a3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction72.C
@@ -0,0 +1,11 @@
+// PR c++/91759
+// { dg-do compile { target c++17 } }
+
+namespace N {
+  template <typename T>
+  struct X{ X(int); };	// { dg-message "declared here" }
+}
+
+using N::X;
+
+X(int) -> X<int>;	// { dg-error "must be declared in the same scope as" }