patch 8.2.3361: Vim9: crash with nested :while

Problem:    Vim9: crash with nested :while.
Solution:   Handle skipping better. (Naruhiko Nishino, closes #8778)

src/testdir/test_vim9_script.vim

@@ -2856,6 +2856,89 @@ def Test_for_loop_with_try_continue()
   CheckDefAndScriptSuccess(lines)
 enddef
 
+def Test_while_skipped_block()
+  # test skipped blocks at outside of function
+  var lines =<< trim END
+    var result = []
+    var n = 0
+    if true
+      n = 1
+      while n < 3
+        result += [n]
+        n += 1
+      endwhile
+    else
+      n = 3
+      while n < 5
+        result += [n]
+        n += 1
+      endwhile
+    endif
+    assert_equal([1, 2], result)
+
+    result = []
+    if false
+      n = 1
+      while n < 3
+        result += [n]
+        n += 1
+      endwhile
+    else
+      n = 3
+      while n < 5
+        result += [n]
+        n += 1
+      endwhile
+    endif
+    assert_equal([3, 4], result)
+  END
+  CheckDefAndScriptSuccess(lines)
+
+  # test skipped blocks at inside of function
+  lines =<< trim END
+    def DefTrue()
+      var result = []
+      var n = 0
+      if true
+        n = 1
+        while n < 3
+          result += [n]
+          n += 1
+        endwhile
+      else
+        n = 3
+        while n < 5
+          result += [n]
+          n += 1
+        endwhile
+      endif
+      assert_equal([1, 2], result)
+    enddef
+    DefTrue()
+
+    def DefFalse()
+      var result = []
+      var n = 0
+      if false
+        n = 1
+        while n < 3
+          result += [n]
+          n += 1
+        endwhile
+      else
+        n = 3
+        while n < 5
+          result += [n]
+          n += 1
+        endwhile
+      endif
+      assert_equal([3, 4], result)
+    enddef
+    DefFalse()
+  END
+  CheckDefAndScriptSuccess(lines)
+enddef
+
 def Test_while_loop()
   var result = ''
   var cnt = 0

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3361,
 /**/
     3360,
 /**/

src/vim9compile.c

@@ -4469,8 +4469,6 @@ compile_subscript(
 	    // dict member: dict[key]
 	    // string index: text[123]
 	    // blob index: blob[123]
-	    // TODO: more arguments
-	    // TODO: recognize list or dict at runtime
 	    if (generate_ppconst(cctx, ppconst) == FAIL)
 		return FAIL;
 	    ppconst->pp_is_const = FALSE;
@@ -8267,22 +8265,26 @@ compile_while(char_u *arg, cctx_T *cctx)
     // compile "expr"
     if (compile_expr0(&p, cctx) == FAIL)
 	return NULL;
+
     if (!ends_excmd2(arg, skipwhite(p)))
     {
 	semsg(_(e_trailing_arg), p);
 	return NULL;
     }
 
-    if (bool_on_stack(cctx) == FAIL)
+    if (cctx->ctx_skip != SKIP_YES)
-	return FAIL;
+    {
+	if (bool_on_stack(cctx) == FAIL)
+	    return FAIL;
 
-    // CMDMOD_REV must come before the jump
+	// CMDMOD_REV must come before the jump
-    generate_undo_cmdmods(cctx);
+	generate_undo_cmdmods(cctx);
 
-    // "while_end" is set when ":endwhile" is found
+	// "while_end" is set when ":endwhile" is found
-    if (compile_jump_to_end(&scope->se_u.se_while.ws_end_label,
+	if (compile_jump_to_end(&scope->se_u.se_while.ws_end_label,
 						  JUMP_IF_FALSE, cctx) == FAIL)
-	return FAIL;
+	    return FAIL;
+    }
 
     return p;
 }
@@ -8304,20 +8306,23 @@ compile_endwhile(char_u *arg, cctx_T *cctx)
 	return NULL;
     }
     cctx->ctx_scope = scope->se_outer;
-    unwind_locals(cctx, scope->se_local_count);
+    if (cctx->ctx_skip != SKIP_YES)
+    {
+	unwind_locals(cctx, scope->se_local_count);
 
 #ifdef FEAT_PROFILE
-    // count the endwhile before jumping
+	// count the endwhile before jumping
-    may_generate_prof_end(cctx, cctx->ctx_lnum);
+	may_generate_prof_end(cctx, cctx->ctx_lnum);
 #endif
 
-    // At end of ":for" scope jump back to the FOR instruction.
+	// At end of ":for" scope jump back to the FOR instruction.
-    generate_JUMP(cctx, JUMP_ALWAYS, scope->se_u.se_while.ws_top_label);
+	generate_JUMP(cctx, JUMP_ALWAYS, scope->se_u.se_while.ws_top_label);
 
-    // Fill in the "end" label in the WHILE statement so it can jump here.
+	// Fill in the "end" label in the WHILE statement so it can jump here.
-    // And in any jumps for ":break"
+	// And in any jumps for ":break"
-    compile_fill_jump_to_end(&scope->se_u.se_while.ws_end_label,
+	compile_fill_jump_to_end(&scope->se_u.se_while.ws_end_label,
 							  instr->ga_len, cctx);
+    }
 
     vim_free(scope);