Merge pull request #4587 from 9rnsr/fix14425

Issue 14425 - Indirect template instantiation within is expression causes missing linker symbols

src/typinf.c

@@ -407,7 +407,7 @@ class TypeInfoDtVisitor : public Visitor
 
     void visit(TypeInfoStructDeclaration *d)
     {
-        //printf("TypeInfoStructDeclaration::toDt() '%s'\n", toChars());
+        //printf("TypeInfoStructDeclaration::toDt() '%s'\n", d->toChars());
         if (global.params.is64bit)
             verifyStructSize(Type::typeinfostruct, 17 * Target::ptrsize);
         else
@@ -424,6 +424,17 @@ class TypeInfoDtVisitor : public Visitor
         if (!sd->members)
             return;
 
+        if (TemplateInstance *ti = sd->isInstantiated())
+        {
+            /* Bugzilla 14425: TypeInfo_Struct would refer the members of
+             * struct (e.g. opEquals via xopEquals field), so if it's instantiated
+             * in speculative context, TypeInfo creation should also be
+             * stopped to avoid 'unresolved symbol' linker errors.
+             */
+            if (!ti->needsCodegen() && !ti->minst)
+                return;
+        }
+
         /* Put out:
          *  char[] name;
          *  void[] init;

test/runnable/link14425.d

@@ -0,0 +1,9 @@
+struct SFoo(I) { I i; }
+struct SBar(I) { I i; }
+static assert(is(SFoo!(SBar!string)));
+
+class CFoo(I) { I i; }
+class CBar(I) { I i; }
+static assert(is(CFoo!(CBar!string)));
+
+void main() {}