add custom assert messages

src/expr/builtin_fn.rs

@@ -83,25 +83,38 @@ pub fn eval_builtin_assert(
     query: &mut expr::EvalFunctionQuery)
     -> Result<expr::Value, ()>
 {
-    query.ensure_arg_number(1)?;
+    query.ensure_min_max_arg_number(1, 2)?;
 
-    let condition = query.args[0].value.expect_bool(
-        query.report,
-        query.args[0].span)?;
+    let condition = query.args[0]
+        .value
+        .expect_bool(
+            query.report,
+            query.args[0].span)?;
 
-    if condition
+    if !condition
     {
-        Ok(expr::Value::Void)
-    }
-    else
-    {
-        let msg = diagn::Message::error_span(
-            "assertion failed",
-            query.span);
+        let msg = {
+            if query.args.len() == 2
+            {
+                diagn::Message::error_span(
+                    format!(
+                        "assertion failed: {}",
+                        query.args[1]
+                            .value
+                            .expect_string(query.report, query.args[1].span)?
+                            .utf8_contents),
+                    query.span)
+            }
+            else {
+                diagn::Message::error_span("assertion failed", query.span)
+            }
+        };
 
-        Ok(expr::Value::FailedConstraint(
-            query.report.wrap_in_parents_capped(msg)))
+        return Ok(expr::Value::FailedConstraint(
+            query.report.wrap_in_parents_capped(msg)));
     }
+
+    Ok(expr::Value::Void)
 }
 
 

src/expr/eval.rs

@@ -219,6 +219,29 @@ impl<'a> EvalFunctionQuery<'a>
 			Ok(())
 		}
 	}
+
+	pub fn ensure_min_max_arg_number(
+		&mut self,
+		minimum_expected_arg_number: usize,
+		maximum_expected_arg_number: usize,
+	) -> Result<(), ()> {
+		if !((self.args.len() >= minimum_expected_arg_number)
+			&& (self.args.len() <= maximum_expected_arg_number))
+		{
+			self.report.error_span(
+				format!(
+					"function expected {} to {} arguments (but got {})",
+					minimum_expected_arg_number,
+					maximum_expected_arg_number,
+					self.args.len()
+				),
+				self.span,
+			);
+			Err(())
+		} else {
+			Ok(())
+		}
+	}
 }
 
 

tests/rule_assert/err_args_too_few.asm

@@ -0,0 +1,10 @@
+#ruledef test
+{
+    ld {x} =>
+    {
+        assert()
+        0x55 @ x`8
+    }
+}
+
+ld 0x15 ; error: failed / note:_:3: within / error:_:5: expected 1 to 2 arguments

tests/rule_assert/err_args_too_many.asm

@@ -0,0 +1,10 @@
+#ruledef test
+{
+    ld {x} =>
+    {
+        assert(x < 0x10, "your custom message!", "another message!")
+        0x55 @ x`8
+    }
+}
+
+ld 0x15 ; error: failed / note:_:3: within / error:_:5: expected 1 to 2 arguments

tests/rule_assert/err_condition_wrong_type.asm

@@ -0,0 +1,10 @@
+#ruledef test
+{
+    ld {x} =>
+    {
+        assert("your custom message!", x < 0x10)
+        0x55 @ x`8
+    }
+}
+
+ld 0x15 ; error: failed / note:_:3: within / error:_:5: expected boolean

tests/rule_assert/err_message.asm

@@ -0,0 +1,10 @@
+#ruledef test
+{
+    ld {x} =>
+    {
+        assert(x < 0x10, "your custom message!")
+        0x55 @ x`8
+    }
+}
+
+ld 0x15 ; error: failed / note:_:3: within / error:_:5: your custom message!

tests/rule_assert/err_message_wrong_type.asm

@@ -0,0 +1,10 @@
+#ruledef test
+{
+    ld {x} =>
+    {
+        assert(x < 0x10, 0x1234)
+        0x55 @ x`8
+    }
+}
+
+ld 0x15 ; error: failed / note:_:3: within / error:_:5: expected string

tests/rule_assert/ok_message.asm

@@ -0,0 +1,11 @@
+#ruledef test
+{
+    ld {x} =>
+    {
+        assert(x < 0x10, "your custom message!")
+        0x55 @ x`8
+    }
+}
+
+ld 0x5 ; = 0x5505
+ld -0x20 ; = 0x55e0