From 72c6dc2bde769740b55ac4e645e18e2bc71fff6d Mon Sep 17 00:00:00 2001
From: sergeych <real.sergeych@gmail.com>
Date: Fri, 21 Nov 2025 17:18:59 +0100
Subject: [PATCH] fixed wrong line report on throw statement

---
 .../kotlin/net/sergeych/lyng/Compiler.kt      | 31 ++++++---
 lynglib/src/commonTest/kotlin/ScriptTest.kt   | 17 +++++
 .../jvmTest/kotlin/ThrowSourcePosJvmTest.kt   | 66 +++++++++++++++++++
 3 files changed, 104 insertions(+), 10 deletions(-)
 create mode 100644 lynglib/src/jvmTest/kotlin/ThrowSourcePosJvmTest.kt

diff --git a/lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt b/lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt
index 59fa4d0..6b3bb19 100644
--- a/lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt
+++ b/lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt
@@ -389,7 +389,7 @@ class Compiler(
                         }
 
                         "throw" -> {
-                            val s = parseThrowStatement()
+                            val s = parseThrowStatement(t.pos)
                             operand = StatementRef(s)
                         }
 
@@ -916,7 +916,7 @@ class Compiler(
         "class" -> parseClassDeclaration()
         "enum" -> parseEnumDeclaration()
         "try" -> parseTryStatement()
-        "throw" -> parseThrowStatement()
+        "throw" -> parseThrowStatement(id.pos)
         "when" -> parseWhenStatement()
         else -> {
             // triples
@@ -1080,15 +1080,26 @@ class Compiler(
         }
     }
 
-    private suspend fun parseThrowStatement(): Statement {
+    private suspend fun parseThrowStatement(start: Pos): Statement {
         val throwStatement = parseStatement() ?: throw ScriptError(cc.currentPos(), "throw object expected")
-        return statement {
-            var errorObject = throwStatement.execute(this)
-            if (errorObject is ObjString)
-                errorObject = ObjException(this, errorObject.value)
-            if (errorObject is ObjException)
-                raiseError(errorObject)
-            else raiseError("this is not an exception object: $errorObject")
+        // Important: bind the created statement to the position of the `throw` keyword so that
+        // any raised error reports the correct source location.
+        return statement(start) { sc ->
+            var errorObject = throwStatement.execute(sc)
+            // Rebind error scope to the throw-site position so ScriptError.pos is accurate
+            val throwScope = sc.createChildScope(pos = start)
+            errorObject = when (errorObject) {
+                is ObjString -> ObjException(throwScope, errorObject.value)
+                is ObjException -> ObjException(
+                    errorObject.exceptionClass,
+                    throwScope,
+                    errorObject.message,
+                    errorObject.extraData,
+                    errorObject.useStackTrace
+                )
+                else -> throwScope.raiseError("this is not an exception object: $errorObject")
+            }
+            throwScope.raiseError(errorObject as ObjException)
         }
     }
 
diff --git a/lynglib/src/commonTest/kotlin/ScriptTest.kt b/lynglib/src/commonTest/kotlin/ScriptTest.kt
index 6a9e50f..a7892dd 100644
--- a/lynglib/src/commonTest/kotlin/ScriptTest.kt
+++ b/lynglib/src/commonTest/kotlin/ScriptTest.kt
@@ -3519,4 +3519,21 @@ class ScriptTest {
         """.trimIndent()).toString())
     }
 
+    @Test
+    fun testThrowReportsSource() = runTest {
+        try {
+            eval(
+                """
+            // line 1
+            // line 2
+            throw "the test"
+        """.trimIndent()
+            )
+        } catch (se: ScriptError) {
+            println(se.message)
+            // Pos.line is zero-based
+            assertEquals(2, se.pos.line)
+        }
+    }
+
 }
diff --git a/lynglib/src/jvmTest/kotlin/ThrowSourcePosJvmTest.kt b/lynglib/src/jvmTest/kotlin/ThrowSourcePosJvmTest.kt
new file mode 100644
index 0000000..b166618
--- /dev/null
+++ b/lynglib/src/jvmTest/kotlin/ThrowSourcePosJvmTest.kt
@@ -0,0 +1,66 @@
+/*
+ * Copyright 2025 Sergey S. Chernov
+ */
+
+import kotlinx.coroutines.runBlocking
+import net.sergeych.lyng.Scope
+import net.sergeych.lyng.ScriptError
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.fail
+
+class ThrowSourcePosJvmTest {
+
+    private fun assertThrowLine(code: String, expectedLine: Int) {
+        try {
+            runBlocking { Scope().eval(code) }
+            fail("Expected ScriptError to be thrown, but nothing was thrown")
+        } catch (se: ScriptError) {
+            println(se.message)
+            assertEquals(expectedLine, se.pos.line)
+        }
+    }
+
+    @Test
+    fun simpleThrow_afterComments_reportsCorrectLine() {
+        val code = """
+            // line 1
+            // line 2
+            throw "simple"
+        """.trimIndent()
+        // zero-based line index
+        assertThrowLine(code, 2)
+    }
+
+    @Test
+    fun inlineThrow_withLeadingSpaces_reportsCorrectLine() {
+        val code = """
+            val x = 1
+                throw "boom"
+        """.trimIndent()
+        // throw is on the 2nd line (zero-based index 1)
+        assertThrowLine(code, 1)
+    }
+
+    @Test
+    fun throwInsideBlock_reportsCorrectLine() {
+        val code = """
+            if( true ) {
+                // comment
+                throw "boom"
+            }
+        """.trimIndent()
+        // throw is on the 3rd line of the snippet (zero-based index 2)
+        assertThrowLine(code, 2)
+    }
+
+    @Test
+    fun throwAsExpression_reportsCorrectLine() {
+        val code = """
+            val x = null
+            val y = x ?: throw "npe-like"
+        """.trimIndent()
+        // throw is on the 2nd line (zero-based index 1)
+        assertThrowLine(code, 1)
+    }
+}