trybuild test of compile fail from README

This has the same error in it twice, and I'm not sure why. Unsatisfying,
but better to test the status quo and hopefully iterate than do nothing.

static-xml-derive/Cargo.toml

@@ -19,3 +19,6 @@ syn = "1.0"
 
 [lib]
 proc-macro = true
+
+[dev-dependencies]
+trybuild = "1.0.71"

static-xml-derive/tests/test.rs

@@ -0,0 +1,5 @@
+#[test]
+fn test() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/ui/field-not-parsetext.rs");
+}

static-xml-derive/tests/ui/field-not-parsetext.rs

@@ -0,0 +1,10 @@
+use static_xml_derive::Deserialize;
+
+struct Foo;
+
+#[derive(Deserialize)]
+struct Outer {
+    foo: Foo,
+}
+
+fn main() {}

static-xml-derive/tests/ui/field-not-parsetext.stderr

@@ -0,0 +1,40 @@
+error[E0277]: the trait bound `Foo: ParseText` is not satisfied
+ --> tests/ui/field-not-parsetext.rs:7:5
+  |
+5 | #[derive(Deserialize)]
+  |          ----------- this tail expression is of type `&mut Foo`
+6 | struct Outer {
+7 |     foo: Foo,
+  |     ^^^^^^^^ the trait `ParseText` is not implemented for `Foo`
+  |
+  = help: the following other types implement trait `ParseText`:
+            String
+            bool
+            f32
+            f64
+            i128
+            i16
+            i32
+            i64
+          and $N others
+  = note: required for `Foo` to implement `Deserialize`
+  = note: required for `Foo` to implement `DeserializeElementField`
+
+error[E0277]: the trait bound `Foo: ParseText` is not satisfied
+ --> tests/ui/field-not-parsetext.rs:7:5
+  |
+7 |     foo: Foo,
+  |     ^^^^^^^^ the trait `ParseText` is not implemented for `Foo`
+  |
+  = help: the following other types implement trait `ParseText`:
+            String
+            bool
+            f32
+            f64
+            i128
+            i16
+            i32
+            i64
+          and $N others
+  = note: required for `Foo` to implement `Deserialize`
+  = note: required for `Foo` to implement `DeserializeElementField`