From dc49b106f376992e63dd49e7f3ed504b225b00a2 Mon Sep 17 00:00:00 2001
From: Eduard Urbach <eduard@urbach.dev>
Date: Wed, 24 Jun 2026 11:20:50 +0200
Subject: [PATCH] Improved error handling for invalid loop controls

---
 src/core/compileLoopControl.go          | 11 +++++++++--
 src/core/errors.go                      | 14 ++++++++++++++
 src/core/errors_test.go                 |  2 ++
 src/core/testdata/InvalidLoopControl.q  |  5 +++++
 src/core/testdata/InvalidLoopControl2.q |  5 +++++
 5 files changed, 35 insertions(+), 2 deletions(-)
 create mode 100644 src/core/testdata/InvalidLoopControl.q
 create mode 100644 src/core/testdata/InvalidLoopControl2.q

diff --git a/src/core/compileLoopControl.go b/src/core/compileLoopControl.go
index 530dee8..fca34e9 100644
--- a/src/core/compileLoopControl.go
+++ b/src/core/compileLoopControl.go
@@ -19,8 +19,9 @@ func (f *Function) compileLoopControl(control *ast.LoopControl) error {
 	}
 
 	loop := f.loopStack.Current()
+	name := call.Children[0].Token.StringFrom(f.File.Bytes)
 
-	switch call.Children[0].Token.StringFrom(f.File.Bytes) {
+	switch name {
 	case "next":
 		f.loopNext(loop)
 	case "restart":
@@ -28,7 +29,13 @@ func (f *Function) compileLoopControl(control *ast.LoopControl) error {
 	case "stop":
 		f.jump(loop.Exit)
 	default:
-		panic("invalid")
+		correctName := ""
+
+		if name == "break" {
+			correctName = "stop"
+		}
+
+		return errors.New(&InvalidLoopControl{Name: name, CorrectName: correctName}, f.File, call.Children[0].Source())
 	}
 
 	return nil
diff --git a/src/core/errors.go b/src/core/errors.go
index a61efe3..8570281 100644
--- a/src/core/errors.go
+++ b/src/core/errors.go
@@ -76,6 +76,20 @@ func (err *IdenticalExpressions) Error() string {
 	return fmt.Sprintf("Identical expressions to the left and right of the '%s' operator", err.Operator)
 }
 
+// InvalidLoopControl represents invalid loop control statements.
+type InvalidLoopControl struct {
+	Name        string
+	CorrectName string
+}
+
+func (err *InvalidLoopControl) Error() string {
+	if err.CorrectName != "" {
+		return fmt.Sprintf("Invalid loop control '%s', did you mean '%s'?", err.Name, err.CorrectName)
+	}
+
+	return fmt.Sprintf("Invalid loop control '%s'", err.Name)
+}
+
 // NoMatchingFunction is created when a function is not defined for the given type.
 type NoMatchingFunction struct {
 	Function string
diff --git a/src/core/errors_test.go b/src/core/errors_test.go
index dae0b2e..cc8019b 100644
--- a/src/core/errors_test.go
+++ b/src/core/errors_test.go
@@ -53,6 +53,8 @@ var errs = []struct {
 	{"InvalidFieldInit.q", core.InvalidFieldInit},
 	{"InvalidFieldInit2.q", core.InvalidFieldInit},
 	{"InvalidLeftExpression.q", core.InvalidLeftExpression},
+	{"InvalidLoopControl.q", &core.InvalidLoopControl{Name: "unknown"}},
+	{"InvalidLoopControl2.q", &core.InvalidLoopControl{Name: "break", CorrectName: "stop"}},
 	{"InvalidLoopHeader.q", core.InvalidLoopHeader},
 	{"InvalidStructOperation.q", core.InvalidStructOperation},
 	{"InvalidStructOperation2.q", core.InvalidStructOperation},
diff --git a/src/core/testdata/InvalidLoopControl.q b/src/core/testdata/InvalidLoopControl.q
new file mode 100644
index 0000000..8b48a32
--- /dev/null
+++ b/src/core/testdata/InvalidLoopControl.q
@@ -0,0 +1,5 @@
+main() {
+	loop {
+		loop.unknown()
+	}
+}
\ No newline at end of file
diff --git a/src/core/testdata/InvalidLoopControl2.q b/src/core/testdata/InvalidLoopControl2.q
new file mode 100644
index 0000000..ccf4dd1
--- /dev/null
+++ b/src/core/testdata/InvalidLoopControl2.q
@@ -0,0 +1,5 @@
+main() {
+	loop {
+		loop.break()
+	}
+}
\ No newline at end of file
-- 
2.51.2