make spec parser stricter

Signed-off-by: Onur Özkan <work@onurozkan.dev>

kaptan-spec/tests/ui/fail_invalid_suffix.rs

@@ -0,0 +1,6 @@
+use kaptan_spec::spec;
+
+#[spec("flight_core_contract.md")]
+struct InvalidSuffix;
+
+fn main() {}

kaptan-spec/tests/ui/fail_invalid_suffix.stderr

@@ -0,0 +1,7 @@
+error: spec path must end in `.spec.md`; use #[spec("file.spec.md")]
+ --> tests/ui/fail_invalid_suffix.rs:3:1
+  |
+3 | #[spec("flight_core_contract.md")]
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the attribute macro `spec` (in Nightly builds, run with -Z macro-backtrace for more info)

kaptan-spec/tests/ui/fail_legacy_named_argument.rs

@@ -0,0 +1,6 @@
+use kaptan_spec::spec;
+
+#[spec(path = "flight_core_contract.spec.md")]
+struct LegacyNamedArgument;
+
+fn main() {}

kaptan-spec/tests/ui/fail_legacy_named_argument.stderr

@@ -0,0 +1,7 @@
+error: invalid spec attribute; use #[spec("file.spec.md")]
+ --> tests/ui/fail_legacy_named_argument.rs:3:1
+  |
+3 | #[spec(path = "flight_core_contract.spec.md")]
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the attribute macro `spec` (in Nightly builds, run with -Z macro-backtrace for more info)

kaptan-spec/tests/ui/fail_missing_argument.rs

@@ -0,0 +1,6 @@
+use kaptan_spec::spec;
+
+#[spec]
+struct MissingArgument;
+
+fn main() {}

kaptan-spec/tests/ui/fail_missing_argument.stderr

@@ -0,0 +1,7 @@
+error: missing spec path; use #[spec("file.spec.md")]
+ --> tests/ui/fail_missing_argument.rs:3:1
+  |
+3 | #[spec]
+  | ^^^^^^^
+  |
+  = note: this error originates in the attribute macro `spec` (in Nightly builds, run with -Z macro-backtrace for more info)

kaptan-spec/tests/ui/fail_missing_sidecar.rs

@@ -1,8 +1,7 @@
 use kaptan_spec::spec;
 
 #[spec("fail_missing_sidecar.spec.md")]
-struct MissingSpec;
+mod missing_spec {}
 
 fn main() {
-    let _ = core::mem::size_of::<MissingSpec>();
 }

kaptan-spec/tests/ui/fail_non_module_item.rs

@@ -0,0 +1,6 @@
+use kaptan_spec::spec;
+
+#[spec("flight_core_contract.spec.md")]
+struct FlightCore;
+
+fn main() {}

kaptan-spec/tests/ui/fail_non_module_item.stderr

@@ -0,0 +1,7 @@
+error: `#[spec]` may only be applied to a module
+ --> tests/ui/fail_non_module_item.rs:3:1
+  |
+3 | #[spec("flight_core_contract.spec.md")]
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the attribute macro `spec` (in Nightly builds, run with -Z macro-backtrace for more info)

kaptan-spec/tests/ui/fail_non_string_argument.rs

@@ -0,0 +1,6 @@
+use kaptan_spec::spec;
+
+#[spec(42)]
+struct NonStringArgument;
+
+fn main() {}

kaptan-spec/tests/ui/fail_non_string_argument.stderr

@@ -0,0 +1,7 @@
+error: invalid spec attribute; use #[spec("file.spec.md")]
+ --> tests/ui/fail_non_string_argument.rs:3:1
+  |
+3 | #[spec(42)]
+  | ^^^^^^^^^^^
+  |
+  = note: this error originates in the attribute macro `spec` (in Nightly builds, run with -Z macro-backtrace for more info)

kaptan-spec/tests/ui/flight_core_contract.rs

@@ -1,9 +1,8 @@
 use kaptan_spec::spec;
 
 #[spec("flight_core_contract.spec.md")]
-struct FlightCore;
+mod flight_core {}
 
 fn main() {
-    let size = core::mem::size_of::<FlightCore>();
-    assert_eq!(size, 0);
+    assert_eq!(core::mem::size_of::<()>(), 0);
 }