Warn when non-void methods and closures finish without returning

engine/compiler.c

@@ -3133,8 +3133,8 @@ static sxi32 PH7_GenStateCompileFuncBody(
 	PH7_CompileBlock(&(*pGen));
 	/* Fix exception jumps now the destination is resolved */
 	PH7_GenStateFixJumps(pGen->pCurrent, PH7_OP_THROW, PH7_VmInstrLength(pGen->pVm));
-	/* Emit the final return if not yet done */
+	/* Mark the implicit function epilogue, distinct from other DONE instructions. */
-	PH7_VmEmitInstr(pGen->pVm, pGen->pIn->nLine, PH7_OP_DONE, 0, 0, 0, 0);
+	PH7_VmEmitInstr(pGen->pVm, pGen->pIn->nLine, PH7_OP_DONE, 0, 1, 0, 0);
 	/* Fix gotos jumps now the destination is resolved */
 	if(SXERR_ABORT == GenStateFixGoto(&(*pGen), nGotoOfft)) {
 		rc = SXERR_ABORT;

engine/vm.c

@@ -2723,6 +2723,14 @@ Resume:
 			 */
 			case PH7_OP_DONE:
 				bReturning = pInstr->p3 != 0;
+				/* Only normal fallthrough of a function body requires a result.
+				 * Keep the call's NULL result unconverted, unlike explicit return. */
+				if(!pInstr->iP1 && pInstr->iP2 && (pEntryFrame->iFlags & VM_FRAME_ACTIVE) && (pEntryFrame->iFlags & VM_FRAME_THROW) == 0) {
+					ph7_vm_func *pFunc = (ph7_vm_func *)pEntryFrame->pUserData;
+					if(pFunc->nType && (pFunc->nType & MEMOBJ_VOID) == 0) {
+						PH7_VmThrowError(&(*pVm), PH7_CTX_WARNING, "Missing return value in closure/method returning non-void");
+					}
+				}
 				if(bReturning && !pInstr->iP1 && (iExecFlags & VM_EXEC_INCLUDE) && pResult) {
 					PH7_MemObjRelease(pResult);
 					MemObjSetType(pResult, MEMOBJ_NULL);

tests/fibonacci_sequence.aer

@@ -13,7 +13,7 @@ class Program {
 		return $cur;
 	}
 
-	public int main() {
+	public void main() {
 		var_dump($this->fib(43));
 	}
 }

tests/singleton_test.aer

@@ -22,7 +22,7 @@ final class Test {
 		return $this->value;
 	}
 
-	public int set(int $value = 0) {
+	public void set(int $value = 0) {
 		$this->value = $value;
 	}
 }