From ee1c43ca919521a8a6b27fee0e9739d0e8e86a55 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Wed, 21 Apr 2021 20:22:16 +0200
Subject: [PATCH] improved scanning for return statement in routines that
 should return a value.

---
 compiler/res/prog8lib/string.p8               |  2 +-
 .../compiler/astprocessing/AstChecker.kt      | 24 ++++++++++++++++++-
 examples/test.p8                              | 24 ++++++++++++-------
 3 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/compiler/res/prog8lib/string.p8 b/compiler/res/prog8lib/string.p8
index d5fc170bf..e54a1aa30 100644
--- a/compiler/res/prog8lib/string.p8
+++ b/compiler/res/prog8lib/string.p8
@@ -178,7 +178,7 @@ _found		sty  P8ZP_SCRATCH_B1
 
     asmsub compare(uword string1 @R0, uword string2 @AY) clobbers(Y) -> byte @A {
         ; Compares two strings for sorting.
-        ; Returns -1 (255), 0 or 1 depeding on wether string1 sorts before, equal or after string2.
+        ; Returns -1 (255), 0 or 1 depending on wether string1 sorts before, equal or after string2.
         ; Note that you can also directly compare strings and string values with eachother using
         ; comparison operators ==, < etcetera (it will use strcmp for you under water automatically).
         %asm {{
diff --git a/compiler/src/prog8/compiler/astprocessing/AstChecker.kt b/compiler/src/prog8/compiler/astprocessing/AstChecker.kt
index 9c5c8dcba..d7f97a0c5 100644
--- a/compiler/src/prog8/compiler/astprocessing/AstChecker.kt
+++ b/compiler/src/prog8/compiler/astprocessing/AstChecker.kt
@@ -196,6 +196,28 @@ internal class AstChecker(private val program: Program,
         super.visit(label)
     }
 
+    private fun hasReturnOrJump(scope: INameScope): Boolean {
+        class Searcher: IAstVisitor
+        {
+            var count=0
+
+            override fun visit(returnStmt: Return) {
+                count++
+            }
+            override fun visit(jump: Jump) {
+                count++
+            }
+        }
+
+        val s=Searcher()
+        for(stmt in scope.statements) {
+            stmt.accept(s)
+            if(s.count>0)
+                return true
+        }
+        return s.count > 0
+    }
+
     override fun visit(subroutine: Subroutine) {
         fun err(msg: String) = errors.err(msg, subroutine.position)
 
@@ -218,7 +240,7 @@ internal class AstChecker(private val program: Program,
 
         // subroutine must contain at least one 'return' or 'goto'
         // (or if it has an asm block, that must contain a 'rts' or 'jmp' or 'bra')
-        if(subroutine.statements.count { it is Return || it is Jump } == 0) {
+        if(!hasReturnOrJump(subroutine)) {
             if (subroutine.amountOfRtsInAsm() == 0) {
                 if (subroutine.returntypes.isNotEmpty()) {
                     // for asm subroutines with an address, no statement check is possible.
diff --git a/examples/test.p8 b/examples/test.p8
index 22c25dc38..5a5a8a92f 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -7,16 +7,22 @@
 main {
 
     sub start() {
-        ubyte xx=existing_entry(1,2)
+        ubyte num_entries
+
+        num_entries = 10
+        ubyte ix
+        for ix in (num_entries-1)*2 downto 0 step -2 {
+            txt.print_ub(ix)
+            txt.spc()
+        }
+
+        txt.nl()
+        num_entries = 10
+        for ix in num_entries-1 downto 0 {
+            txt.print_ub(ix*2)
+            txt.spc()
+        }
     }
 
-    ; TODO FIX COMPILER ERROR ABOUT MISSING RETURN
-
-    sub existing_entry(ubyte hash, uword symbol) -> ubyte {
-        if hash>10
-            return 44
-        else
-            return false
-    }
 }