compiler warning for unreachable code following a call to exit()

compiler/src/prog8/ast/processing/AstChecker.kt

@@ -327,6 +327,8 @@ internal class AstChecker(private val program: Program,
                 err("Pass-by-reference types (str, array) cannot occur as a parameter type directly. Instead, use an uword for their address, or access the variable from the outer scope directly.")
             }
         }
+
+        visitStatements(subroutine.statements)
     }
 
     override fun visit(repeatLoop: RepeatLoop) {
@@ -1040,6 +1042,20 @@ internal class AstChecker(private val program: Program,
         }
     }
 
+    override fun visit(scope: AnonymousScope) {
+        visitStatements(scope.statements)
+    }
+
+    private fun visitStatements(statements: List<Statement>) {
+        for((index, stmt) in statements.withIndex()) {
+            if(stmt is FunctionCallStatement && stmt.target.nameInSource.last()=="exit") {
+                if(index < statements.size-1) {
+                    printWarning("unreachable code", statements[index+1].position, "exit call above never returns")
+                }
+            }
+        }
+    }
+
     private fun checkFunctionOrLabelExists(target: IdentifierReference, statement: Statement): Statement? {
         val targetStatement = target.targetStatement(program.namespace)
         if(targetStatement is Label || targetStatement is Subroutine || targetStatement is BuiltinFunctionStatementPlaceholder)

docs/source/todo.rst

@@ -3,7 +3,6 @@ TODO
 ====
 
 - option to load library files from a directory instead of the embedded ones
-- compiler warning 'unreachable code' for statement following an exit() function call
 - code optimizer: remove all statements following an exit() function call
 - vector inc/dec/add/sub/mul/div...?
         arrayvar++ / arrayvar-- / arrayvar += 2 / arrayvar -= 2 / arrayvar *= 3 / arrayvar /= 3

examples/test.p8

@@ -21,9 +21,9 @@ main {
         c64scr.print("sp2:")
         print_stackpointer()
         exit(65)
-        sub3()          ; TODO unreachable code compiler warning + remove the code in optimizer
-        sub3()          ; TODO unreachable code compiler warning + remove the code in optimizer
-        sub3()          ; TODO unreachable code compiler warning + remove the code in optimizer
+        sub3()          ; TODO  remove the code in optimizer
+        sub3()          ; TODO  remove the code in optimizer
+        sub3()          ; TODO  remove the code in optimizer
     }
 
     sub sub3() {