Fix issue #21640: @LiVe not working with templates

Signed-off-by: Luís Ferreira <contact@lsferreira.net>

src/dmd/mtype.d

@@ -4267,6 +4267,7 @@ extern (C++) final class TypeFunction : TypeNext
         t.mod = mod;
         t.isnothrow = isnothrow;
         t.isnogc = isnogc;
+        t.islive = islive;
         t.purity = purity;
         t.isproperty = isproperty;
         t.isref = isref;

test/compilable/ob2.d

@@ -0,0 +1,44 @@
+// REQUIRED_ARGS: -preview=dip1021
+
+void* malloc();
+
+@live T* foo1(T)(T* p)
+{
+    return p;   // consumes owner
+}
+
+@live T* foo2(T)()
+{
+    T* p = null;
+    return p;      // consumes owner
+}
+
+@live T* foo3(T)(T* p)
+{
+    scope T* q = p;  // borrows from p
+    return p;          // use of p ends borrow in q
+}
+
+@live T* foo4(T)(T* p)
+{
+    scope T* bq = p;          // borrow
+    scope const T* cq = p;    // const borrow
+    return p;                   // ends both borrows
+}
+
+@live T* foo5(T)()
+{
+    auto p = cast(T*) malloc();
+    scope b = p;
+    return p;
+}
+
+void test()
+{
+    int* p;
+    foo1!int(p);
+    foo2!int();
+    foo3!int(p);
+    foo4!int(p);
+    foo5!int();
+}

test/fail_compilation/failob2.d

@@ -0,0 +1,67 @@
+// REQUIRED_ARGS: -preview=dip1021
+
+/*
+TEST_OUTPUT:
+---
+fail_compilation/failob2.d(105): Error: variable `failob2.foo1!int.foo1.p` has undefined state and cannot be read
+fail_compilation/failob2.d(105): Error: variable `failob2.foo1!int.foo1.p` is returned but is Undefined
+fail_compilation/failob2.d(124): Error: template instance `failob2.foo1!int` error instantiating
+fail_compilation/failob2.d(111): Error: variable `failob2.foo2!int.foo2.p` has undefined state and cannot be read
+fail_compilation/failob2.d(111): Error: variable `failob2.foo2!int.foo2.p` is returned but is Undefined
+fail_compilation/failob2.d(125): Error: template instance `failob2.foo2!int` error instantiating
+fail_compilation/failob2.d(119): Error: variable `failob2.foo3!int.foo3.p` has undefined state and cannot be read
+fail_compilation/failob2.d(119): Error: variable `failob2.foo3!int.foo3.p` is returned but is Undefined
+fail_compilation/failob2.d(126): Error: template instance `failob2.foo3!int` error instantiating
+---
+*/
+
+#line 100
+
+@live
+T* foo1(T)()
+{
+    T* p = void;
+    return p;
+}
+
+template foo2(T) {
+    @live T* foo2() {
+        T* p = void;
+        return p;
+    }
+}
+
+@live
+template foo3(T) {
+    T* foo3() {
+        T* p = void;
+        return p;
+    }
+}
+
+void test1() {
+    foo1!int();
+    foo2!int();
+    foo3!int();
+}
+
+/*
+TEST_OUTPUT:
+---
+fail_compilation/failob2.d(205): Error: variable `failob2.foo4!int.foo4.p` is left dangling at return
+fail_compilation/failob2.d(209): Error: template instance `failob2.foo4!int` error instantiating
+---
+*/
+
+#line 200
+
+void* alloc(size_t);
+
+@live void foo4(T)()
+{
+    auto p = alloc(4);
+}
+
+void test2() {
+    foo4!int();
+}