patch 8.2.1274: Vim9: no error for missing white space at script level

Problem:    Vim9: no error for missing white space in assignment at script
            level.
Solution:   Check for white space. (closes #6495)
diff --git a/src/testdir/test_let.vim b/src/testdir/test_let.vim
index 404fe15..9a399e8 100644
--- a/src/testdir/test_let.vim
+++ b/src/testdir/test_let.vim
@@ -293,12 +293,12 @@
   let s = "var"
   let var = 1
   call assert_fails('let var += [1,2]', 'E734:')
-  call assert_fails('let {s}.1 = 2', 'E18:')
+  call assert_fails('let {s}.1 = 2', 'E15:')
   call assert_fails('let a[1] = 5', 'E121:')
   let l = [[1,2]]
   call assert_fails('let l[:][0] = [5]', 'E708:')
   let d = {'k' : 4}
-  call assert_fails('let d.# = 5', 'E713:')
+  call assert_fails('let d.# = 5', 'E488:')
   call assert_fails('let d.m += 5', 'E734:')
   call assert_fails('let m = d[{]', 'E15:')
   let l = [1, 2]
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 36d7e89..fd572d7 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -318,6 +318,15 @@
   call CheckDefFailure(['let var =234'], 'E1004:')
   call CheckDefFailure(['let var= 234'], 'E1004:')
 
+  call CheckScriptFailure(['vim9script', 'let var=234'], 'E1004:')
+  call CheckScriptFailure(['vim9script', 'let var=234'], "before and after '='")
+  call CheckScriptFailure(['vim9script', 'let var =234'], 'E1004:')
+  call CheckScriptFailure(['vim9script', 'let var= 234'], 'E1004:')
+  call CheckScriptFailure(['vim9script', 'let var = 234', 'var+=234'], 'E1004:')
+  call CheckScriptFailure(['vim9script', 'let var = 234', 'var+=234'], "before and after '+='")
+  call CheckScriptFailure(['vim9script', 'let var = "x"', 'var..="y"'], 'E1004:')
+  call CheckScriptFailure(['vim9script', 'let var = "x"', 'var..="y"'], "before and after '..='")
+
   call CheckDefFailure(['let true = 1'], 'E1034:')
   call CheckDefFailure(['let false = 1'], 'E1034:')