Merge pull request #10257 from Geod24/fixup-pr-10256

[stable]  Fixup PR 10256: Properly nest substituted C++ names in N..E
merged-on-behalf-of: Nicholas Wilson <[email protected]>

Author: dlang-bot

src/dmd/cppmangle.d

@@ -236,7 +236,24 @@ private final class CppMangleVisitor : Visitor
         }
     }
 
-    bool substitute(RootObject p)
+    /**
+     * Attempt to perform substitution on `p`
+     *
+     * If `p` already appeared in the mangling, it is stored as
+     * a 'part', and short references in the form of `SX_` can be used.
+     * Note that `p` can be anything: template declaration, struct declaration,
+     * class declaration, namespace...
+     *
+     * Params:
+     *   p = The object to attempt to substitute
+     *   nested = Whether or not `p` is to be considered nested.
+     *            When `true`, `N` will be prepended before the substitution.
+     *
+     * Returns:
+     *   Whether `p` already appeared in the mangling,
+     *   and substitution has been written to `this.buf`.
+     */
+    bool substitute(RootObject p, bool nested = false)
     {
         //printf("substitute %s\n", p ? p.toChars() : null);
         auto i = find(p);
@@ -245,6 +262,8 @@ private final class CppMangleVisitor : Visitor
             //printf("\tmatch\n");
             /* Sequence is S_, S0_, .., S9_, SA_, ..., SZ_, S10_, ...
              */
+            if (nested)
+                buf.writeByte('N');
             buf.writeByte('S');
             writeSequenceFromIndex(i);
             buf.writeByte('_');
@@ -551,8 +570,13 @@ private final class CppMangleVisitor : Visitor
         if (TemplateInstance ti = s.isTemplateInstance())
         {
             bool needsTa = false;
-            if (substitute(ti.tempdecl))
+            const isNested = !!ti.tempdecl.namespace || !!getQualifier(ti.tempdecl);
+            if (substitute(ti.tempdecl, !haveNE && isNested))
+            {
                 template_args(ti);
+                if (!haveNE && isNested)
+                    buf.writeByte('E');
+            }
             else if (this.writeStdSubstitution(ti, needsTa))
             {
                 if (needsTa)
@@ -812,7 +836,6 @@ private final class CppMangleVisitor : Visitor
                         isChar((*ti.tiargs)[0]) &&
                         isChar_traits_char((*ti.tiargs)[1]) &&
                         isAllocator_char((*ti.tiargs)[2]))
-
                     {
                         buf.writestring("Ss");
                         return;

test/compilable/cppmangle.d

@@ -1166,5 +1166,5 @@ version (Posix)
     }
 
     extern(C++) void test20094(xvector20094!(V20094)* v);
-    static assert(test20094.mangleof == `_Z9test20094PN7ns2009412xvector20094IS0_IhEEE`);
+    static assert(test20094.mangleof == `_Z9test20094PN7ns2009412xvector20094INS0_IhEEEE`);
 }