diff --git a/compiler/src/dmd/dtemplate.d b/compiler/src/dmd/dtemplate.d
index 465ae7453cdc..1006df2bac65 100644
--- a/compiler/src/dmd/dtemplate.d
+++ b/compiler/src/dmd/dtemplate.d
@@ -916,93 +916,6 @@ extern (C++) final class TemplateDeclaration : ScopeDsymbol
         return o;
     }
 
-    /*************************************************
-     * Limited function template instantiation for using fd.leastAsSpecialized()
-     */
-    extern (D) FuncDeclaration doHeaderInstantiation(TemplateInstance ti, Scope* sc2, FuncDeclaration fd, Type tthis, Expressions* fargs)
-    {
-        assert(fd);
-        version (none)
-        {
-            printf("doHeaderInstantiation this = %s\n", toChars());
-        }
-
-        // function body and contracts are not need
-        if (fd.isCtorDeclaration())
-            fd = new CtorDeclaration(fd.loc, fd.endloc, fd.storage_class, fd.type.syntaxCopy());
-        else
-            fd = new FuncDeclaration(fd.loc, fd.endloc, fd.ident, fd.storage_class, fd.type.syntaxCopy());
-        fd.parent = ti;
-
-        assert(fd.type.ty == Tfunction);
-        auto tf = fd.type.isTypeFunction();
-        tf.fargs = fargs;
-
-        if (tthis)
-        {
-            // Match 'tthis' to any TemplateThisParameter's
-            bool hasttp = false;
-            foreach (tp; *parameters)
-            {
-                TemplateThisParameter ttp = tp.isTemplateThisParameter();
-                if (ttp)
-                    hasttp = true;
-            }
-            if (hasttp)
-            {
-                tf = tf.addSTC(ModToStc(tthis.mod)).isTypeFunction();
-                assert(!tf.deco);
-            }
-        }
-
-        Scope* scx = sc2.push();
-
-        // Shouldn't run semantic on default arguments and return type.
-        foreach (ref params; *tf.parameterList.parameters)
-            params.defaultArg = null;
-        tf.incomplete = true;
-
-        if (fd.isCtorDeclaration())
-        {
-            // For constructors, emitting return type is necessary for
-            // isReturnIsolated() in functionResolve.
-            tf.isctor = true;
-
-            Dsymbol parent = toParentDecl();
-            Type tret;
-            AggregateDeclaration ad = parent.isAggregateDeclaration();
-            if (!ad || parent.isUnionDeclaration())
-            {
-                tret = Type.tvoid;
-            }
-            else
-            {
-                tret = ad.handleType();
-                assert(tret);
-                tret = tret.addStorageClass(fd.storage_class | scx.stc);
-                tret = tret.addMod(tf.mod);
-            }
-            tf.next = tret;
-            if (ad && ad.isStructDeclaration())
-                tf.isref = 1;
-            //printf("tf = %s\n", tf.toChars());
-        }
-        else
-            tf.next = null;
-        fd.type = tf;
-        fd.type = fd.type.addSTC(scx.stc);
-        fd.type = fd.type.typeSemantic(fd.loc, scx);
-        scx = scx.pop();
-
-        if (fd.type.ty != Tfunction)
-            return null;
-
-        fd.originalType = fd.type; // for mangling
-        //printf("\t[%s] fd.type = %s, mod = %x, ", loc.toChars(), fd.type.toChars(), fd.type.mod);
-        //printf("fd.needThis() = %d\n", fd.needThis());
-
-        return fd;
-    }
 
     debug (FindExistingInstance)
     {
diff --git a/compiler/src/dmd/templatesem.d b/compiler/src/dmd/templatesem.d
index 1942afe44ae2..ec29ad6997fe 100644
--- a/compiler/src/dmd/templatesem.d
+++ b/compiler/src/dmd/templatesem.d
@@ -1468,7 +1468,7 @@ Lmatch:
         sc2.minst = sc.minst;
         sc2.stc |= fd.storage_class & STC.deprecated_;
 
-        fd = td.doHeaderInstantiation(ti, sc2, fd, tthis, argumentList.arguments);
+        fd = doHeaderInstantiation(td, ti, sc2, fd, tthis, argumentList.arguments);
         sc2 = sc2.pop();
         sc2 = sc2.pop();
 
@@ -1495,3 +1495,92 @@ Lmatch:
     //printf("\tmatch %d\n", match);
     return MATCHpair(matchTiargs, match);
 }
+
+/*************************************************
+ * Limited function template instantiation for using fd.leastAsSpecialized()
+ */
+private
+FuncDeclaration doHeaderInstantiation(TemplateDeclaration td, TemplateInstance ti, Scope* sc2, FuncDeclaration fd, Type tthis, Expressions* fargs)
+{
+    assert(fd);
+    version (none)
+    {
+        printf("doHeaderInstantiation this = %s\n", toChars());
+    }
+
+    // function body and contracts are not need
+    if (fd.isCtorDeclaration())
+        fd = new CtorDeclaration(fd.loc, fd.endloc, fd.storage_class, fd.type.syntaxCopy());
+    else
+        fd = new FuncDeclaration(fd.loc, fd.endloc, fd.ident, fd.storage_class, fd.type.syntaxCopy());
+    fd.parent = ti;
+
+    assert(fd.type.ty == Tfunction);
+    auto tf = fd.type.isTypeFunction();
+    tf.fargs = fargs;
+
+    if (tthis)
+    {
+        // Match 'tthis' to any TemplateThisParameter's
+        bool hasttp = false;
+        foreach (tp; *td.parameters)
+        {
+            TemplateThisParameter ttp = tp.isTemplateThisParameter();
+            if (ttp)
+                hasttp = true;
+        }
+        if (hasttp)
+        {
+            tf = tf.addSTC(ModToStc(tthis.mod)).isTypeFunction();
+            assert(!tf.deco);
+        }
+    }
+
+    Scope* scx = sc2.push();
+
+    // Shouldn't run semantic on default arguments and return type.
+    foreach (ref params; *tf.parameterList.parameters)
+        params.defaultArg = null;
+    tf.incomplete = true;
+
+    if (fd.isCtorDeclaration())
+    {
+        // For constructors, emitting return type is necessary for
+        // isReturnIsolated() in functionResolve.
+        tf.isctor = true;
+
+        Dsymbol parent = td.toParentDecl();
+        Type tret;
+        AggregateDeclaration ad = parent.isAggregateDeclaration();
+        if (!ad || parent.isUnionDeclaration())
+        {
+            tret = Type.tvoid;
+        }
+        else
+        {
+            tret = ad.handleType();
+            assert(tret);
+            tret = tret.addStorageClass(fd.storage_class | scx.stc);
+            tret = tret.addMod(tf.mod);
+        }
+        tf.next = tret;
+        if (ad && ad.isStructDeclaration())
+            tf.isref = 1;
+        //printf("tf = %s\n", tf.toChars());
+    }
+    else
+        tf.next = null;
+    fd.type = tf;
+    fd.type = fd.type.addSTC(scx.stc);
+    fd.type = fd.type.typeSemantic(fd.loc, scx);
+    scx = scx.pop();
+
+    if (fd.type.ty != Tfunction)
+        return null;
+
+    fd.originalType = fd.type; // for mangling
+    //printf("\t[%s] fd.type = %s, mod = %x, ", loc.toChars(), fd.type.toChars(), fd.type.mod);
+    //printf("fd.needThis() = %d\n", fd.needThis());
+
+    return fd;
+}