export_fn: add "name" parameter

codegen/ui_tests/export_fn_bad_attr.rs

@@ -0,0 +1,24 @@
+use rhai::plugin::*;
+
+#[derive(Clone)]
+struct Point {
+    x: f32,
+    y: f32,
+}
+
+#[export_fn(unknown = true)]
+pub fn test_fn(input: Point) -> bool {
+    input.x > input.y
+}
+
+fn main() {
+    let n = Point {
+        x: 0.0,
+        y: 10.0,
+    };
+    if test_fn(n) {
+        println!("yes");
+    } else {
+        println!("no");
+    }
+}

codegen/ui_tests/export_fn_bad_attr.stderr

@@ -0,0 +1,11 @@
+error: unknown attribute 'unknown'
+ --> $DIR/export_fn_bad_attr.rs:9:13
+  |
+9 | #[export_fn(unknown = true)]
+  |             ^^^^^^^
+
+error[E0425]: cannot find function `test_fn` in this scope
+  --> $DIR/export_fn_bad_attr.rs:19:8
+   |
+19 |     if test_fn(n) {
+   |        ^^^^^^^ not found in this scope

codegen/ui_tests/export_fn_bad_value.rs

@@ -0,0 +1,24 @@
+use rhai::plugin::*;
+
+#[derive(Clone)]
+struct Point {
+    x: f32,
+    y: f32,
+}
+
+#[export_fn(name = true)]
+pub fn test_fn(input: Point) -> bool {
+    input.x > input.y
+}
+
+fn main() {
+    let n = Point {
+        x: 0.0,
+        y: 10.0,
+    };
+    if test_fn(n) {
+        println!("yes");
+    } else {
+        println!("no");
+    }
+}

codegen/ui_tests/export_fn_bad_value.stderr

@@ -0,0 +1,11 @@
+error: expecting string literal value
+ --> $DIR/export_fn_bad_value.rs:9:20
+  |
+9 | #[export_fn(name = true)]
+  |                    ^^^^
+
+error[E0425]: cannot find function `test_fn` in this scope
+  --> $DIR/export_fn_bad_value.rs:19:8
+   |
+19 |     if test_fn(n) {
+   |        ^^^^^^^ not found in this scope

codegen/ui_tests/export_fn_junk_arg.rs

@@ -0,0 +1,24 @@
+use rhai::plugin::*;
+
+#[derive(Clone)]
+struct Point {
+    x: f32,
+    y: f32,
+}
+
+#[export_fn("wheeeee")]
+pub fn test_fn(input: Point) -> bool {
+    input.x > input.y
+}
+
+fn main() {
+    let n = Point {
+        x: 0.0,
+        y: 10.0,
+    };
+    if test_fn(n) {
+        println!("yes");
+    } else {
+        println!("no");
+    }
+}

codegen/ui_tests/export_fn_junk_arg.stderr

@@ -0,0 +1,11 @@
+error: expected assignment expression
+ --> $DIR/export_fn_junk_arg.rs:9:13
+  |
+9 | #[export_fn("wheeeee")]
+  |             ^^^^^^^^^
+
+error[E0425]: cannot find function `test_fn` in this scope
+  --> $DIR/export_fn_junk_arg.rs:19:8
+   |
+19 |     if test_fn(n) {
+   |        ^^^^^^^ not found in this scope