patch 8.2.3312: Vim9: after "if false" line breaks in expression not skipped

Problem:    Vim9: after "if false" line breaks in expression not skipped.
Solution:   Do parse the expression. (closes #8723)

Author: brammool

src/testdir/test_vim9_script.vim

@@ -2372,6 +2372,14 @@ def Test_if_const_expr()
   if false
     burp
   endif
+
+  # expression with line breaks skipped
+  if false
+      ('aaa'
+      .. 'bbb'
+      .. 'ccc'
+      )->setline(1)
+  endif
 enddef
 
 def Test_if_const_expr_fails()

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3312,
 /**/
     3311,
 /**/

src/vim9compile.c

@@ -9730,14 +9730,12 @@ compile_def_function(
 
 	if (p == ea.cmd && ea.cmdidx != CMD_SIZE)
 	{
-	    if (cctx.ctx_skip == SKIP_YES)
+	    if (cctx.ctx_skip == SKIP_YES && ea.cmdidx != CMD_eval)
 	    {
 		line += STRLEN(line);
 		goto nextline;
 	    }
-
-	    // Expression or function call.
-	    if (ea.cmdidx != CMD_eval)
+	    else if (ea.cmdidx != CMD_eval)
 	    {
 		// CMD_var cannot happen, compile_assignment() above would be
 		// used.  Most likely an assignment to a non-existing variable.