fix Issue 10920 - template instantiation order dependent link failure…

… problem

src/template.c

@@ -5690,6 +5690,12 @@ void TemplateInstance::semantic(Scope *sc, Expressions *fargs)
 
     // Get the instantiating module from the scope minst
     minst = sc->minst;
+    // Bugzilla 10920: If the enclosing function is non-root symbol,
+    // this instance should be speculative.
+    if (!tinst && sc->func && !sc->func->isInstantiated() && sc->func->inNonRoot())
+    {
+        minst = NULL;
+    }
 
     gagged = (global.gag > 0);
 

test/runnable/imports/link10920a.d

@@ -0,0 +1,19 @@
+module imports.link10920a;
+
+struct FormatSpec(C)
+{
+    void func() {}
+}
+
+struct BitArray
+{
+    auto toString()
+    {
+        // An auto function may runs semantic3 to calculate return type,
+        // even if it's non-root symbol.
+        // But inside the function body, all instantiations should be treated
+        // as speculative.
+        FormatSpec!char fs;
+        fs.func();
+    }
+}

test/runnable/link10920.d

@@ -0,0 +1,19 @@
+// PERMUTE_ARGS: -version=A
+
+// It's imported but won't be linked.
+import imports.link10920a;
+
+void main()
+{
+    BitArray ba;
+    version(A)
+    {
+        // Run semantic3 of BitArray.toString()
+        // before the FormatSpec instantiation in main().
+        pragma(msg, typeof(ba.toString()));
+    }
+
+    // The instance codegen should be run always, unrelated with -version=A.
+    FormatSpec!char fs;
+    fs.func();
+}