diag(preview=in): Don't mention rvalue for in parameter with preview=in (dlang#21411)

Because the compiler can pass rvalues to ref parameters with preview=in,
it is confusing and potentially misleading to have it mention rvalues.

Author: Geod24

compiler/src/dmd/typesem.d

@@ -1196,7 +1196,7 @@ private const(char)* getParamError(TypeFunction tf, Expression arg, Parameter pa
     auto at = qual ? arg.type.toPrettyChars(true) : arg.type.toChars();
     OutBuffer buf;
     // only mention rvalue if it's relevant
-    const rv = !arg.isLvalue() && par.isReference();
+    const rv = !arg.isLvalue() && par.isReference() && !(par.storageClass & STC.constscoperef);
     buf.printf("cannot pass %sargument `%s` of type `%s` to parameter `%s`",
         rv ? "rvalue ".ptr : "".ptr, arg.toErrMsg(), at,
         parameterToChars(par, tf, qual));

compiler/test/fail_compilation/previewin3.d

@@ -0,0 +1,19 @@
+/*
+REQUIRED_ARGS: -preview=in -preview=dip1000
+TEST_OUTPUT:
+----
+fail_compilation/previewin3.d(2): Error: function `foo` is not callable using argument types `(int)`
+fail_compilation/previewin3.d(2):        cannot pass argument `42` of type `int` to parameter `in WithDtor`
+fail_compilation/previewin3.d(8):        `previewin3.foo(in WithDtor)` declared here
+----
+ */
+
+#line 1
+void rvalueErrorMsg () {
+    foo(42);
+}
+
+// Add a dtor to ensure things are passed by ref
+struct WithDtor { ~this() @safe pure nothrow @nogc {} }
+
+void foo(in WithDtor) {}