diff --git a/src/globals.h b/src/globals.h
index 59f22d1..1a6a0d8 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -379,39 +379,39 @@
 
 
 // Commonly used types.
-EXTERN type_T t_any INIT5(VAR_UNKNOWN, 0, 0, NULL, NULL);
-EXTERN type_T t_void INIT5(VAR_VOID, 0, 0, NULL, NULL);
-EXTERN type_T t_bool INIT5(VAR_BOOL, 0, 0, NULL, NULL);
-EXTERN type_T t_special INIT5(VAR_SPECIAL, 0, 0, NULL, NULL);
-EXTERN type_T t_number INIT5(VAR_NUMBER, 0, 0, NULL, NULL);
-EXTERN type_T t_float INIT5(VAR_FLOAT, 0, 0, NULL, NULL);
-EXTERN type_T t_string INIT5(VAR_STRING, 0, 0, NULL, NULL);
-EXTERN type_T t_blob INIT5(VAR_BLOB, 0, 0, NULL, NULL);
-EXTERN type_T t_job INIT5(VAR_JOB, 0, 0, NULL, NULL);
-EXTERN type_T t_channel INIT5(VAR_CHANNEL, 0, 0, NULL, NULL);
+EXTERN type_T t_any INIT6(VAR_UNKNOWN, 0, 0, 0, NULL, NULL);
+EXTERN type_T t_void INIT6(VAR_VOID, 0, 0, 0, NULL, NULL);
+EXTERN type_T t_bool INIT6(VAR_BOOL, 0, 0, 0, NULL, NULL);
+EXTERN type_T t_special INIT6(VAR_SPECIAL, 0, 0, 0, NULL, NULL);
+EXTERN type_T t_number INIT6(VAR_NUMBER, 0, 0, 0, NULL, NULL);
+EXTERN type_T t_float INIT6(VAR_FLOAT, 0, 0, 0, NULL, NULL);
+EXTERN type_T t_string INIT6(VAR_STRING, 0, 0, 0, NULL, NULL);
+EXTERN type_T t_blob INIT6(VAR_BLOB, 0, 0, 0, NULL, NULL);
+EXTERN type_T t_job INIT6(VAR_JOB, 0, 0, 0, NULL, NULL);
+EXTERN type_T t_channel INIT6(VAR_CHANNEL, 0, 0, 0, NULL, NULL);
 
-EXTERN type_T t_func_void INIT5(VAR_FUNC, -1, 0, &t_void, NULL);
-EXTERN type_T t_func_any INIT5(VAR_FUNC, -1, 0, &t_any, NULL);
-EXTERN type_T t_func_number INIT5(VAR_FUNC, -1, 0, &t_number, NULL);
-EXTERN type_T t_func_string INIT5(VAR_FUNC, -1, 0, &t_string, NULL);
-EXTERN type_T t_func_0_void INIT5(VAR_FUNC, 0, 0, &t_void, NULL);
-EXTERN type_T t_func_0_any INIT5(VAR_FUNC, 0, 0, &t_any, NULL);
-EXTERN type_T t_func_0_number INIT5(VAR_FUNC, 0, 0, &t_number, NULL);
-EXTERN type_T t_func_0_string INIT5(VAR_FUNC, 0, 0, &t_string, NULL);
+EXTERN type_T t_func_void INIT6(VAR_FUNC, -1, 0, 0, &t_void, NULL);
+EXTERN type_T t_func_any INIT6(VAR_FUNC, -1, 0, 0, &t_any, NULL);
+EXTERN type_T t_func_number INIT6(VAR_FUNC, -1, 0, 0, &t_number, NULL);
+EXTERN type_T t_func_string INIT6(VAR_FUNC, -1, 0, 0, &t_string, NULL);
+EXTERN type_T t_func_0_void INIT6(VAR_FUNC, 0, 0, 0, &t_void, NULL);
+EXTERN type_T t_func_0_any INIT6(VAR_FUNC, 0, 0, 0, &t_any, NULL);
+EXTERN type_T t_func_0_number INIT6(VAR_FUNC, 0, 0, 0, &t_number, NULL);
+EXTERN type_T t_func_0_string INIT6(VAR_FUNC, 0, 0, 0, &t_string, NULL);
 
-EXTERN type_T t_list_any INIT5(VAR_LIST, 0, 0, &t_any, NULL);
-EXTERN type_T t_dict_any INIT5(VAR_DICT, 0, 0, &t_any, NULL);
-EXTERN type_T t_list_empty INIT5(VAR_LIST, 0, 0, &t_void, NULL);
-EXTERN type_T t_dict_empty INIT5(VAR_DICT, 0, 0, &t_void, NULL);
+EXTERN type_T t_list_any INIT6(VAR_LIST, 0, 0, 0, &t_any, NULL);
+EXTERN type_T t_dict_any INIT6(VAR_DICT, 0, 0, 0, &t_any, NULL);
+EXTERN type_T t_list_empty INIT6(VAR_LIST, 0, 0, 0, &t_void, NULL);
+EXTERN type_T t_dict_empty INIT6(VAR_DICT, 0, 0, 0, &t_void, NULL);
 
-EXTERN type_T t_list_bool INIT5(VAR_LIST, 0, 0, &t_bool, NULL);
-EXTERN type_T t_list_number INIT5(VAR_LIST, 0, 0, &t_number, NULL);
-EXTERN type_T t_list_string INIT5(VAR_LIST, 0, 0, &t_string, NULL);
-EXTERN type_T t_list_dict_any INIT5(VAR_LIST, 0, 0, &t_dict_any, NULL);
+EXTERN type_T t_list_bool INIT6(VAR_LIST, 0, 0, 0, &t_bool, NULL);
+EXTERN type_T t_list_number INIT6(VAR_LIST, 0, 0, 0, &t_number, NULL);
+EXTERN type_T t_list_string INIT6(VAR_LIST, 0, 0, 0, &t_string, NULL);
+EXTERN type_T t_list_dict_any INIT6(VAR_LIST, 0, 0, 0, &t_dict_any, NULL);
 
-EXTERN type_T t_dict_bool INIT5(VAR_DICT, 0, 0, &t_bool, NULL);
-EXTERN type_T t_dict_number INIT5(VAR_DICT, 0, 0, &t_number, NULL);
-EXTERN type_T t_dict_string INIT5(VAR_DICT, 0, 0, &t_string, NULL);
+EXTERN type_T t_dict_bool INIT6(VAR_DICT, 0, 0, 0, &t_bool, NULL);
+EXTERN type_T t_dict_number INIT6(VAR_DICT, 0, 0, 0, &t_number, NULL);
+EXTERN type_T t_dict_string INIT6(VAR_DICT, 0, 0, 0, &t_string, NULL);
 
 
 #endif
diff --git a/src/structs.h b/src/structs.h
index efc74da..4a51281 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1341,10 +1341,11 @@
 typedef struct type_S type_T;
 struct type_S {
     vartype_T	    tt_type;
-    short	    tt_argcount;    // for func, partial, -1 for unknown
-    short	    tt_flags;	    // TTFLAG_ values
+    char	    tt_argcount;    // for func, -1 for unknown
+    char	    tt_min_argcount; // number of non-optional arguments
+    char	    tt_flags;	    // TTFLAG_ values
     type_T	    *tt_member;	    // for list, dict, func return type
-    type_T	    **tt_args;	    // func arguments, allocated
+    type_T	    **tt_args;	    // func argument types, allocated
 };
 
 #define TTFLAG_VARARGS	1	    // func args ends with "..."
@@ -1520,7 +1521,7 @@
     int		uf_calls;	// nr of active calls
     int		uf_cleared;	// func_clear() was already called
     int		uf_dfunc_idx;	// >= 0 for :def function only
-    garray_T	uf_args;	// arguments
+    garray_T	uf_args;	// arguments, including optional arguments
     garray_T	uf_def_args;	// default argument expressions
 
     // for :def (for :function uf_ret_type is NULL)
@@ -1531,6 +1532,7 @@
 				// uf_def_args; length: uf_def_args.ga_len + 1
     char_u	*uf_va_name;	// name from "...name" or NULL
     type_T	*uf_va_type;	// type from "...name: type" or NULL
+    type_T	*uf_func_type;	// type of the function, &t_func_any if unknown
 
     garray_T	uf_lines;	// function lines
 # ifdef FEAT_PROFILE
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index d0bfe1c..1a47cfc 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -274,6 +274,7 @@
 	test_vartabs \
 	test_vim9_disassemble \
 	test_vim9_expr \
+	test_vim9_func \
 	test_vim9_script \
 	test_viminfo \
 	test_vimscript \
@@ -483,6 +484,7 @@
 	test_vartabs.res \
 	test_vim9_disassemble.res \
 	test_vim9_expr.res \
+	test_vim9_func.res \
 	test_vim9_script.res \
 	test_viminfo.res \
 	test_vimscript.res \
diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index e71782b..0299df5 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -87,8 +87,10 @@
 def Test_disassemble_store()
   let res = execute('disass s:ScriptFuncStore')
   assert_match('<SNR>\d*_ScriptFuncStore.*'
+        \ .. 'let localnr = 1.*'
         \ .. 'localnr = 2.*'
         \ .. ' STORE 2 in $0.*'
+        \ .. 'let localstr = ''abc''.*'
         \ .. 'localstr = ''xyz''.*'
         \ .. ' STORE $1.*'
         \ .. 'v:char = ''abc''.*'
@@ -360,22 +362,22 @@
 enddef
 
 def WithFunc()
-  let funky1: func
-  let funky2: func = function("len")
-  let party2: func = funcref("UserFunc")
+  let Funky1: func
+  let Funky2: func = function("len")
+  let Party2: func = funcref("UserFunc")
 enddef
 
 def Test_disassemble_function()
   let instr = execute('disassemble WithFunc')
   assert_match('WithFunc.*'
-        \ .. 'let funky1: func.*'
+        \ .. 'let Funky1: func.*'
         \ .. '0 PUSHFUNC "\[none]".*'
         \ .. '1 STORE $0.*'
-        \ .. 'let funky2: func = function("len").*'
+        \ .. 'let Funky2: func = function("len").*'
         \ .. '2 PUSHS "len".*'
         \ .. '3 BCALL function(argc 1).*'
         \ .. '4 STORE $1.*'
-        \ .. 'let party2: func = funcref("UserFunc").*'
+        \ .. 'let Party2: func = funcref("UserFunc").*'
         \ .. '\d PUSHS "UserFunc".*'
         \ .. '\d BCALL funcref(argc 1).*'
         \ .. '\d STORE $2.*'
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index d9c20ac..f11fc83 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -460,8 +460,8 @@
 
   call CheckDefFailureMult(['let j: job', 'let chan: channel', 'let r = j == chan'], 'Cannot compare job with channel')
   call CheckDefFailureMult(['let j: job', 'let x: list<any>', 'let r = j == x'], 'Cannot compare job with list')
-  call CheckDefFailureMult(['let j: job', 'let x: func', 'let r = j == x'], 'Cannot compare job with func')
-  call CheckDefFailureMult(['let j: job', 'let x: func', 'let r = j == x'], 'Cannot compare job with func')
+  call CheckDefFailureMult(['let j: job', 'let Xx: func', 'let r = j == Xx'], 'Cannot compare job with func')
+  call CheckDefFailureMult(['let j: job', 'let Xx: func', 'let r = j == Xx'], 'Cannot compare job with func')
 endfunc
 
 " test addition, subtraction, concatenation
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
new file mode 100644
index 0000000..6f61254
--- /dev/null
+++ b/src/testdir/test_vim9_func.vim
@@ -0,0 +1,400 @@
+" Test various aspects of the Vim9 script language.
+
+source check.vim
+source view_util.vim
+
+" Check that "lines" inside ":def" results in an "error" message.
+func CheckDefFailure(lines, error)
+  call writefile(['def Func()'] + a:lines + ['enddef'], 'Xdef')
+  call assert_fails('so Xdef', a:error, a:lines)
+  call delete('Xdef')
+endfunc
+
+func CheckScriptFailure(lines, error)
+  call writefile(a:lines, 'Xdef')
+  call assert_fails('so Xdef', a:error, a:lines)
+  call delete('Xdef')
+endfunc
+
+func Test_def_basic()
+  def SomeFunc(): string
+    return 'yes'
+  enddef
+  call assert_equal('yes', SomeFunc())
+endfunc
+
+def ReturnString(): string
+  return 'string'
+enddef
+
+def ReturnNumber(): number
+  return 123
+enddef
+
+let g:notNumber = 'string'
+
+def ReturnGlobal(): number
+  return g:notNumber
+enddef
+
+def Test_return_something()
+  assert_equal('string', ReturnString())
+  assert_equal(123, ReturnNumber())
+  assert_fails('call ReturnGlobal()', 'E1029: Expected number but got string')
+enddef
+
+let s:nothing = 0
+def ReturnNothing()
+  s:nothing = 1
+  if true
+    return
+  endif
+  s:nothing = 2
+enddef
+
+def Test_return_nothing()
+  ReturnNothing()
+  assert_equal(1, s:nothing)
+enddef
+
+func Increment()
+  let g:counter += 1
+endfunc
+
+def Test_call_ufunc_count()
+  g:counter = 1
+  Increment()
+  Increment()
+  Increment()
+  " works with and without :call
+  assert_equal(4, g:counter)
+  call assert_equal(4, g:counter)
+  unlet g:counter
+enddef
+
+def MyVarargs(arg: string, ...rest: list<string>): string
+  let res = arg
+  for s in rest
+    res ..= ',' .. s
+  endfor
+  return res
+enddef
+
+def Test_call_varargs()
+  assert_equal('one', MyVarargs('one'))
+  assert_equal('one,two', MyVarargs('one', 'two'))
+  assert_equal('one,two,three', MyVarargs('one', 'two', 'three'))
+enddef
+
+def MyDefaultArgs(name = 'string'): string
+  return name
+enddef
+
+def Test_call_default_args()
+  assert_equal('string', MyDefaultArgs())
+  assert_equal('one', MyDefaultArgs('one'))
+  assert_fails('call MyDefaultArgs("one", "two")', 'E118:')
+
+  call CheckScriptFailure(['def Func(arg: number = asdf)', 'enddef'], 'E1001:')
+enddef
+
+func Test_call_default_args_from_func()
+  call assert_equal('string', MyDefaultArgs())
+  call assert_equal('one', MyDefaultArgs('one'))
+  call assert_fails('call MyDefaultArgs("one", "two")', 'E118:')
+endfunc
+
+func TakesOneArg(arg)
+  echo a:arg
+endfunc
+
+def Test_call_wrong_args()
+  call CheckDefFailure(['TakesOneArg()'], 'E119:')
+  call CheckDefFailure(['TakesOneArg(11, 22)'], 'E118:')
+  call CheckDefFailure(['bufnr(xxx)'], 'E1001:')
+enddef
+
+" Default arg and varargs
+def MyDefVarargs(one: string, two = 'foo', ...rest: list<string>): string
+  let res = one .. ',' .. two
+  for s in rest
+    res ..= ',' .. s
+  endfor
+  return res
+enddef
+
+def Test_call_def_varargs()
+  call assert_fails('call MyDefVarargs()', 'E119:')
+  assert_equal('one,foo', MyDefVarargs('one'))
+  assert_equal('one,two', MyDefVarargs('one', 'two'))
+  assert_equal('one,two,three', MyDefVarargs('one', 'two', 'three'))
+enddef
+
+def Test_using_var_as_arg()
+  call writefile(['def Func(x: number)',  'let x = 234', 'enddef'], 'Xdef')
+  call assert_fails('so Xdef', 'E1006:')
+  call delete('Xdef')
+enddef
+
+def Test_call_func_defined_later()
+  call assert_equal('one', DefinedLater('one'))
+  call assert_fails('call NotDefined("one")', 'E117:')
+enddef
+
+func DefinedLater(arg)
+  return a:arg
+endfunc
+
+def FuncWithForwardCall()
+  return DefinedEvenLater("yes")
+enddef
+
+def DefinedEvenLater(arg: string): string
+  return arg
+enddef
+
+def Test_error_in_nested_function()
+  " Error in called function requires unwinding the call stack.
+  assert_fails('call FuncWithForwardCall()', 'E1029')
+enddef
+
+def Test_return_type_wrong()
+  CheckScriptFailure(['def Func(): number', 'return "a"', 'enddef'], 'expected number but got string')
+  CheckScriptFailure(['def Func(): string', 'return 1', 'enddef'], 'expected string but got number')
+  CheckScriptFailure(['def Func(): void', 'return "a"', 'enddef'], 'expected void but got string')
+  CheckScriptFailure(['def Func()', 'return "a"', 'enddef'], 'expected void but got string')
+
+  CheckScriptFailure(['def Func(): number', 'return', 'enddef'], 'E1003:')
+
+  CheckScriptFailure(['def Func(): list', 'return []', 'enddef'], 'E1008:')
+  CheckScriptFailure(['def Func(): dict', 'return {}', 'enddef'], 'E1008:')
+enddef
+
+def Test_arg_type_wrong()
+  CheckScriptFailure(['def Func3(items: list)', 'echo "a"', 'enddef'], 'E1008: Missing <type>')
+enddef
+
+def Test_vim9script_call()
+  let lines =<< trim END
+    vim9script
+    let var = ''
+    def MyFunc(arg: string)
+       var = arg
+    enddef
+    MyFunc('foobar')
+    assert_equal('foobar', var)
+
+    let str = 'barfoo'
+    str->MyFunc()
+    assert_equal('barfoo', var)
+
+    let g:value = 'value'
+    g:value->MyFunc()
+    assert_equal('value', var)
+
+    let listvar = []
+    def ListFunc(arg: list<number>)
+       listvar = arg
+    enddef
+    [1, 2, 3]->ListFunc()
+    assert_equal([1, 2, 3], listvar)
+
+    let dictvar = {}
+    def DictFunc(arg: dict<number>)
+       dictvar = arg
+    enddef
+    {'a': 1, 'b': 2}->DictFunc()
+    assert_equal(#{a: 1, b: 2}, dictvar)
+    def CompiledDict()
+      {'a': 3, 'b': 4}->DictFunc()
+    enddef
+    CompiledDict()
+    assert_equal(#{a: 3, b: 4}, dictvar)
+
+    #{a: 3, b: 4}->DictFunc()
+    assert_equal(#{a: 3, b: 4}, dictvar)
+
+    ('text')->MyFunc()
+    assert_equal('text', var)
+    ("some")->MyFunc()
+    assert_equal('some', var)
+  END
+  writefile(lines, 'Xcall.vim')
+  source Xcall.vim
+  delete('Xcall.vim')
+enddef
+
+def Test_vim9script_call_fail_decl()
+  let lines =<< trim END
+    vim9script
+    let var = ''
+    def MyFunc(arg: string)
+       let var = 123
+    enddef
+  END
+  writefile(lines, 'Xcall_decl.vim')
+  assert_fails('source Xcall_decl.vim', 'E1054:')
+  delete('Xcall_decl.vim')
+enddef
+
+def Test_vim9script_call_fail_const()
+  let lines =<< trim END
+    vim9script
+    const var = ''
+    def MyFunc(arg: string)
+       var = 'asdf'
+    enddef
+  END
+  writefile(lines, 'Xcall_const.vim')
+  assert_fails('source Xcall_const.vim', 'E46:')
+  delete('Xcall_const.vim')
+enddef
+
+" Test that inside :function a Python function can be defined, :def is not
+" recognized.
+func Test_function_python()
+  CheckFeature python3
+  let py = 'python3'
+  execute py "<< EOF"
+def do_something():
+  return 1
+EOF
+endfunc
+
+def Test_delfunc()
+  let lines =<< trim END
+    vim9script
+    def GoneSoon()
+      echo 'hello'
+    enddef
+
+    def CallGoneSoon()
+      GoneSoon()
+    enddef
+
+    delfunc GoneSoon
+    CallGoneSoon()
+  END
+  writefile(lines, 'XToDelFunc')
+  assert_fails('so XToDelFunc', 'E933')
+  assert_fails('so XToDelFunc', 'E933')
+
+  delete('XToDelFunc')
+enddef
+
+def Test_redef_failure()
+  call writefile(['def Func0(): string',  'return "Func0"', 'enddef'], 'Xdef')
+  so Xdef
+  call writefile(['def Func1(): string',  'return "Func1"', 'enddef'], 'Xdef')
+  so Xdef
+  call writefile(['def! Func0(): string', 'enddef'], 'Xdef')
+  call assert_fails('so Xdef', 'E1027:')
+  call writefile(['def Func2(): string',  'return "Func2"', 'enddef'], 'Xdef')
+  so Xdef
+  call delete('Xdef')
+
+  call assert_equal(0, Func0())
+  call assert_equal('Func1', Func1())
+  call assert_equal('Func2', Func2())
+
+  delfunc! Func0
+  delfunc! Func1
+  delfunc! Func2
+enddef
+
+" Test for internal functions returning different types
+func Test_InternalFuncRetType()
+  let lines =<< trim END
+    def RetFloat(): float
+      return ceil(1.456)
+    enddef
+
+    def RetListAny(): list<any>
+      return items({'k' : 'v'})
+    enddef
+
+    def RetListString(): list<string>
+      return split('a:b:c', ':')
+    enddef
+
+    def RetListDictAny(): list<dict<any>>
+      return getbufinfo()
+    enddef
+
+    def RetDictNumber(): dict<number>
+      return wordcount()
+    enddef
+
+    def RetDictString(): dict<string>
+      return environ()
+    enddef
+  END
+  call writefile(lines, 'Xscript')
+  source Xscript
+
+  call assert_equal(2.0, RetFloat())
+  call assert_equal([['k', 'v']], RetListAny())
+  call assert_equal(['a', 'b', 'c'], RetListString())
+  call assert_notequal([], RetListDictAny())
+  call assert_notequal({}, RetDictNumber())
+  call assert_notequal({}, RetDictString())
+  call delete('Xscript')
+endfunc
+
+" Test for passing too many or too few arguments to internal functions
+func Test_internalfunc_arg_error()
+  let l =<< trim END
+    def! FArgErr(): float
+      return ceil(1.1, 2)
+    enddef
+  END
+  call writefile(l, 'Xinvalidarg')
+  call assert_fails('so Xinvalidarg', 'E118:')
+  let l =<< trim END
+    def! FArgErr(): float
+      return ceil()
+    enddef
+  END
+  call writefile(l, 'Xinvalidarg')
+  call assert_fails('so Xinvalidarg', 'E119:')
+  call delete('Xinvalidarg')
+endfunc
+
+let s:funcResult = 0
+
+def FuncNoArgNoRet()
+  funcResult = 11
+enddef
+
+def FuncNoArgRetNumber(): number
+  funcResult = 22
+  return 1234
+enddef
+
+def FuncOneArgNoRet(arg: number)
+  funcResult = arg
+enddef
+
+def FuncOneArgRetNumber(arg: number): number
+  funcResult = arg
+  return arg
+enddef
+
+def Test_func_type()
+  let Ref1: func()
+  funcResult = 0
+  Ref1 = FuncNoArgNoRet
+  Ref1()
+  assert_equal(11, funcResult)
+enddef
+
+def Test_func_type_fails()
+  CheckDefFailure(['let ref1: func()'], 'E704:')
+
+  CheckDefFailure(['let Ref1: func()', 'Ref1 = FuncNoArgRetNumber'], 'E1013: type mismatch, expected func() but got func(): number')
+  CheckDefFailure(['let Ref1: func()', 'Ref1 = FuncOneArgNoRet'], 'E1013: type mismatch, expected func() but got func(number)')
+  CheckDefFailure(['let Ref1: func()', 'Ref1 = FuncOneArgRetNumber'], 'E1013: type mismatch, expected func() but got func(number): number')
+enddef
+
+
+" vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index cf12e85..01579a8 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -21,13 +21,6 @@
   let other: list<string> = ['asdf']
 enddef
 
-func Test_def_basic()
-  def SomeFunc(): string
-    return 'yes'
-  enddef
-  call assert_equal('yes', SomeFunc())
-endfunc
-
 let s:appendToMe = 'xxx'
 let s:addToMe = 111
 let g:existing = 'yes'
@@ -66,9 +59,9 @@
   if has('float')
     let float1: float = 3.4
   endif
-  let funky1: func
-  let funky2: func = function('len')
-  let party2: func = funcref('Test_syntax')
+  let Funky1: func
+  let Funky2: func = function('len')
+  let Party2: func = funcref('Test_syntax')
 
   " type becomes list<any>
   let somelist = rand() > 0 ? [1, 2, 3] : ['a', 'b', 'c']
@@ -134,6 +127,9 @@
   assert_equal('noneagain', v:errmsg)
   call CheckDefFailure(['v:errmsg += "more"'], 'E1013:')
   call CheckDefFailure(['v:errmsg += 123'], 'E1013:')
+enddef
+
+def Test_assignment_default()
 
   " Test default values.
   let thebool: bool
@@ -153,8 +149,8 @@
   let theblob: blob
   assert_equal(0z, theblob)
 
-  let thefunc: func
-  assert_equal(test_null_function(), thefunc)
+  let Thefunc: func
+  assert_equal(test_null_function(), Thefunc)
 
   let thelist: list<any>
   assert_equal([], thelist)
@@ -264,157 +260,6 @@
 enddef
 
 
-def ReturnString(): string
-  return 'string'
-enddef
-
-def ReturnNumber(): number
-  return 123
-enddef
-
-let g:notNumber = 'string'
-
-def ReturnGlobal(): number
-  return g:notNumber
-enddef
-
-def Test_return_something()
-  assert_equal('string', ReturnString())
-  assert_equal(123, ReturnNumber())
-  assert_fails('call ReturnGlobal()', 'E1029: Expected number but got string')
-enddef
-
-let s:nothing = 0
-def ReturnNothing()
-  s:nothing = 1
-  if true
-    return
-  endif
-  s:nothing = 2
-enddef
-
-def Test_return_nothing()
-  ReturnNothing()
-  assert_equal(1, s:nothing)
-enddef
-
-func Increment()
-  let g:counter += 1
-endfunc
-
-def Test_call_ufunc_count()
-  g:counter = 1
-  Increment()
-  Increment()
-  Increment()
-  " works with and without :call
-  assert_equal(4, g:counter)
-  call assert_equal(4, g:counter)
-  unlet g:counter
-enddef
-
-def MyVarargs(arg: string, ...rest: list<string>): string
-  let res = arg
-  for s in rest
-    res ..= ',' .. s
-  endfor
-  return res
-enddef
-
-def Test_call_varargs()
-  assert_equal('one', MyVarargs('one'))
-  assert_equal('one,two', MyVarargs('one', 'two'))
-  assert_equal('one,two,three', MyVarargs('one', 'two', 'three'))
-enddef
-
-def MyDefaultArgs(name = 'string'): string
-  return name
-enddef
-
-def Test_call_default_args()
-  assert_equal('string', MyDefaultArgs())
-  assert_equal('one', MyDefaultArgs('one'))
-  assert_fails('call MyDefaultArgs("one", "two")', 'E118:')
-
-  call CheckScriptFailure(['def Func(arg: number = asdf)', 'enddef'], 'E1001:')
-enddef
-
-func Test_call_default_args_from_func()
-  call assert_equal('string', MyDefaultArgs())
-  call assert_equal('one', MyDefaultArgs('one'))
-  call assert_fails('call MyDefaultArgs("one", "two")', 'E118:')
-endfunc
-
-func TakesOneArg(arg)
-  echo a:arg
-endfunc
-
-def Test_call_wrong_args()
-  call CheckDefFailure(['TakesOneArg()'], 'E119:')
-  call CheckDefFailure(['TakesOneArg(11, 22)'], 'E118:')
-  call CheckDefFailure(['bufnr(xxx)'], 'E1001:')
-enddef
-
-" Default arg and varargs
-def MyDefVarargs(one: string, two = 'foo', ...rest: list<string>): string
-  let res = one .. ',' .. two
-  for s in rest
-    res ..= ',' .. s
-  endfor
-  return res
-enddef
-
-def Test_call_def_varargs()
-  call assert_fails('call MyDefVarargs()', 'E119:')
-  assert_equal('one,foo', MyDefVarargs('one'))
-  assert_equal('one,two', MyDefVarargs('one', 'two'))
-  assert_equal('one,two,three', MyDefVarargs('one', 'two', 'three'))
-enddef
-
-def Test_using_var_as_arg()
-  call writefile(['def Func(x: number)',  'let x = 234', 'enddef'], 'Xdef')
-  call assert_fails('so Xdef', 'E1006:')
-  call delete('Xdef')
-enddef
-
-def Test_call_func_defined_later()
-  call assert_equal('one', DefinedLater('one'))
-  call assert_fails('call NotDefined("one")', 'E117:')
-enddef
-
-func DefinedLater(arg)
-  return a:arg
-endfunc
-
-def FuncWithForwardCall()
-  return DefinedEvenLater("yes")
-enddef
-
-def DefinedEvenLater(arg: string): string
-  return arg
-enddef
-
-def Test_error_in_nested_function()
-  " Error in called function requires unwinding the call stack.
-  assert_fails('call FuncWithForwardCall()', 'E1029')
-enddef
-
-def Test_return_type_wrong()
-  CheckScriptFailure(['def Func(): number', 'return "a"', 'enddef'], 'expected number but got string')
-  CheckScriptFailure(['def Func(): string', 'return 1', 'enddef'], 'expected string but got number')
-  CheckScriptFailure(['def Func(): void', 'return "a"', 'enddef'], 'expected void but got string')
-  CheckScriptFailure(['def Func()', 'return "a"', 'enddef'], 'expected void but got string')
-
-  CheckScriptFailure(['def Func(): number', 'return', 'enddef'], 'E1003:')
-
-  CheckScriptFailure(['def Func(): list', 'return []', 'enddef'], 'E1008:')
-  CheckScriptFailure(['def Func(): dict', 'return {}', 'enddef'], 'E1008:')
-enddef
-
-def Test_arg_type_wrong()
-  CheckScriptFailure(['def Func3(items: list)', 'echo "a"', 'enddef'], 'E1008: Missing <type>')
-enddef
-
 def Test_try_catch()
   let l = []
   try
@@ -732,82 +577,6 @@
   assert_fails('export something', 'E1042')
 enddef
 
-def Test_vim9script_call()
-  let lines =<< trim END
-    vim9script
-    let var = ''
-    def MyFunc(arg: string)
-       var = arg
-    enddef
-    MyFunc('foobar')
-    assert_equal('foobar', var)
-
-    let str = 'barfoo'
-    str->MyFunc()
-    assert_equal('barfoo', var)
-
-    let g:value = 'value'
-    g:value->MyFunc()
-    assert_equal('value', var)
-
-    let listvar = []
-    def ListFunc(arg: list<number>)
-       listvar = arg
-    enddef
-    [1, 2, 3]->ListFunc()
-    assert_equal([1, 2, 3], listvar)
-
-    let dictvar = {}
-    def DictFunc(arg: dict<number>)
-       dictvar = arg
-    enddef
-    {'a': 1, 'b': 2}->DictFunc()
-    assert_equal(#{a: 1, b: 2}, dictvar)
-    def CompiledDict()
-      {'a': 3, 'b': 4}->DictFunc()
-    enddef
-    CompiledDict()
-    assert_equal(#{a: 3, b: 4}, dictvar)
-
-    #{a: 3, b: 4}->DictFunc()
-    assert_equal(#{a: 3, b: 4}, dictvar)
-
-    ('text')->MyFunc()
-    assert_equal('text', var)
-    ("some")->MyFunc()
-    assert_equal('some', var)
-  END
-  writefile(lines, 'Xcall.vim')
-  source Xcall.vim
-  delete('Xcall.vim')
-enddef
-
-def Test_vim9script_call_fail_decl()
-  let lines =<< trim END
-    vim9script
-    let var = ''
-    def MyFunc(arg: string)
-       let var = 123
-    enddef
-  END
-  writefile(lines, 'Xcall_decl.vim')
-  assert_fails('source Xcall_decl.vim', 'E1054:')
-  delete('Xcall_decl.vim')
-enddef
-
-def Test_vim9script_call_fail_const()
-  let lines =<< trim END
-    vim9script
-    const var = ''
-    def MyFunc(arg: string)
-       var = 'asdf'
-    enddef
-  END
-  writefile(lines, 'Xcall_const.vim')
-  assert_fails('source Xcall_const.vim', 'E46:')
-  delete('Xcall_const.vim')
-enddef
-
 def Test_vim9script_reload()
   let lines =<< trim END
     vim9script
@@ -926,17 +695,6 @@
   assert_equal([2, 99, 3, 4, 5], l)
 enddef
 
-" Test that inside :function a Python function can be defined, :def is not
-" recognized.
-func Test_function_python()
-  CheckFeature python3
-  let py = 'python3'
-  execute py "<< EOF"
-def do_something():
-  return 1
-EOF
-endfunc
-
 def IfElse(what: number): string
   let res = ''
   if what == 1
@@ -1087,27 +845,6 @@
   call CheckDefFailure(["if has('aaa') ? true false"], 'E109:')
 enddef
 
-def Test_delfunc()
-  let lines =<< trim END
-    vim9script
-    def GoneSoon()
-      echo 'hello'
-    enddef
-
-    def CallGoneSoon()
-      GoneSoon()
-    enddef
-
-    delfunc GoneSoon
-    CallGoneSoon()
-  END
-  writefile(lines, 'XToDelFunc')
-  assert_fails('so XToDelFunc', 'E933')
-  assert_fails('so XToDelFunc', 'E933')
-
-  delete('XToDelFunc')
-enddef
-
 def Test_execute_cmd()
   new
   setline(1, 'default')
@@ -1222,83 +959,6 @@
   assert_true(caught, 'should have caught an exception')
 enddef
 
-def Test_redef_failure()
-  call writefile(['def Func0(): string',  'return "Func0"', 'enddef'], 'Xdef')
-  so Xdef
-  call writefile(['def Func1(): string',  'return "Func1"', 'enddef'], 'Xdef')
-  so Xdef
-  call writefile(['def! Func0(): string', 'enddef'], 'Xdef')
-  call assert_fails('so Xdef', 'E1027:')
-  call writefile(['def Func2(): string',  'return "Func2"', 'enddef'], 'Xdef')
-  so Xdef
-  call delete('Xdef')
-
-  call assert_equal(0, Func0())
-  call assert_equal('Func1', Func1())
-  call assert_equal('Func2', Func2())
-
-  delfunc! Func0
-  delfunc! Func1
-  delfunc! Func2
-enddef
-
-" Test for internal functions returning different types
-func Test_InternalFuncRetType()
-  let lines =<< trim END
-    def RetFloat(): float
-      return ceil(1.456)
-    enddef
-
-    def RetListAny(): list<any>
-      return items({'k' : 'v'})
-    enddef
-
-    def RetListString(): list<string>
-      return split('a:b:c', ':')
-    enddef
-
-    def RetListDictAny(): list<dict<any>>
-      return getbufinfo()
-    enddef
-
-    def RetDictNumber(): dict<number>
-      return wordcount()
-    enddef
-
-    def RetDictString(): dict<string>
-      return environ()
-    enddef
-  END
-  call writefile(lines, 'Xscript')
-  source Xscript
-
-  call assert_equal(2.0, RetFloat())
-  call assert_equal([['k', 'v']], RetListAny())
-  call assert_equal(['a', 'b', 'c'], RetListString())
-  call assert_notequal([], RetListDictAny())
-  call assert_notequal({}, RetDictNumber())
-  call assert_notequal({}, RetDictString())
-  call delete('Xscript')
-endfunc
-
-" Test for passing too many or too few arguments to internal functions
-func Test_internalfunc_arg_error()
-  let l =<< trim END
-    def! FArgErr(): float
-      return ceil(1.1, 2)
-    enddef
-  END
-  call writefile(l, 'Xinvalidarg')
-  call assert_fails('so Xinvalidarg', 'E118:')
-  let l =<< trim END
-    def! FArgErr(): float
-      return ceil()
-    enddef
-  END
-  call writefile(l, 'Xinvalidarg')
-  call assert_fails('so Xinvalidarg', 'E119:')
-  call delete('Xinvalidarg')
-endfunc
 
 " Keep this last, it messes up highlighting.
 def Test_substitute_cmd()
diff --git a/src/userfunc.c b/src/userfunc.c
index 71591eb..cff86da 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -951,6 +951,9 @@
     VIM_CLEAR(fp->uf_arg_types);
     VIM_CLEAR(fp->uf_def_arg_idx);
     VIM_CLEAR(fp->uf_va_name);
+    while (fp->uf_type_list.ga_len > 0)
+	vim_free(((type_T **)fp->uf_type_list.ga_data)
+						  [--fp->uf_type_list.ga_len]);
     ga_clear(&fp->uf_type_list);
 #ifdef FEAT_PROFILE
     VIM_CLEAR(fp->uf_tml_count);
@@ -3013,6 +3016,7 @@
     fp->uf_args = newargs;
     fp->uf_def_args = default_args;
     fp->uf_ret_type = &t_any;
+    fp->uf_func_type = &t_func_any;
 
     if (eap->cmdidx == CMD_def)
     {
@@ -3022,7 +3026,7 @@
 	SOURCING_LNUM = sourcing_lnum_top;
 
 	// parse the argument types
-	ga_init2(&fp->uf_type_list, sizeof(type_T), 5);
+	ga_init2(&fp->uf_type_list, sizeof(type_T *), 10);
 
 	if (argtypes.ga_len > 0)
 	{
diff --git a/src/version.c b/src/version.c
index 076d032..034c66b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    512,
+/**/
     511,
 /**/
     510,
diff --git a/src/vim.h b/src/vim.h
index f986666..535a18d 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1751,6 +1751,7 @@
 # define INIT3(a, b, c)
 # define INIT4(a, b, c, d)
 # define INIT5(a, b, c, d, e)
+# define INIT6(a, b, c, d, e, f)
 #else
 # ifndef INIT
 #  define INIT(x) x
@@ -1758,6 +1759,7 @@
 #  define INIT3(a, b, c) = {a, b, c}
 #  define INIT4(a, b, c, d) = {a, b, c, d}
 #  define INIT5(a, b, c, d, e) = {a, b, c, d, e}
+#  define INIT6(a, b, c, d, e, f) = {a, b, c, d, e, f}
 #  define DO_INIT
 # endif
 #endif
diff --git a/src/vim9.h b/src/vim9.h
index a414caa..0c59b06 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -29,8 +29,8 @@
     ISN_STORE,	    // pop into local variable isn_arg.number
     ISN_STOREV,	    // pop into v: variable isn_arg.number
     ISN_STOREG,	    // pop into global variable isn_arg.string
-    ISN_STORES,	    // pop into scirpt variable isn_arg.loadstore
-    ISN_STORESCRIPT, // pop into scirpt variable isn_arg.script
+    ISN_STORES,	    // pop into script variable isn_arg.loadstore
+    ISN_STORESCRIPT, // pop into script variable isn_arg.script
     ISN_STOREOPT,   // pop into option isn_arg.string
     ISN_STOREENV,    // pop into environment variable isn_arg.string
     ISN_STOREREG,    // pop into register isn_arg.number
@@ -191,7 +191,7 @@
 
 // arguments to ISN_LOADS and ISN_STORES
 typedef struct {
-    char_u	*ls_name;	// variable name
+    char_u	*ls_name;	// variable name (with s: for ISN_STORES)
     int		ls_sid;		// script ID
 } loadstore_T;
 
diff --git a/src/vim9compile.c b/src/vim9compile.c
index b64f8ef..b040fd1 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -120,7 +120,7 @@
     scope_T	*ctx_scope;	    // current scope, NULL at toplevel
 
     garray_T	ctx_type_stack;	    // type of each item on the stack
-    garray_T	*ctx_type_list;	    // space for adding types
+    garray_T	*ctx_type_list;	    // list of pointers to allocated types
 };
 
 static char e_var_notfound[] = N_("E1001: variable not found: %s");
@@ -223,6 +223,26 @@
     return OK;
 }
 
+/*
+ * Allocate memory for a type_T and add the pointer to type_gap, so that it can
+ * be freed later.
+ */
+    static type_T *
+alloc_type(garray_T *type_gap)
+{
+    type_T *type;
+
+    if (ga_grow(type_gap, 1) == FAIL)
+	return NULL;
+    type = ALLOC_CLEAR_ONE(type_T);
+    if (type != NULL)
+    {
+	((type_T **)type_gap->ga_data)[type_gap->ga_len] = type;
+	++type_gap->ga_len;
+    }
+    return type;
+}
+
     static type_T *
 get_list_type(type_T *member_type, garray_T *type_gap)
 {
@@ -241,10 +261,9 @@
 	return &t_list_string;
 
     // Not a common type, create a new entry.
-    if (ga_grow(type_gap, 1) == FAIL)
+    type = alloc_type(type_gap);
+    if (type == NULL)
 	return &t_any;
-    type = ((type_T *)type_gap->ga_data) + type_gap->ga_len;
-    ++type_gap->ga_len;
     type->tt_type = VAR_LIST;
     type->tt_member = member_type;
     type->tt_argcount = 0;
@@ -270,10 +289,9 @@
 	return &t_dict_string;
 
     // Not a common type, create a new entry.
-    if (ga_grow(type_gap, 1) == FAIL)
+    type = alloc_type(type_gap);
+    if (type == NULL)
 	return &t_any;
-    type = ((type_T *)type_gap->ga_data) + type_gap->ga_len;
-    ++type_gap->ga_len;
     type->tt_type = VAR_DICT;
     type->tt_member = member_type;
     type->tt_argcount = 0;
@@ -325,10 +343,9 @@
     }
 
     // Not a common type or has arguments, create a new entry.
-    if (ga_grow(type_gap, 1) == FAIL)
+    type = alloc_type(type_gap);
+    if (type == NULL)
 	return &t_any;
-    type = ((type_T *)type_gap->ga_data) + type_gap->ga_len;
-    ++type_gap->ga_len;
     type->tt_type = VAR_FUNC;
     type->tt_member = ret_type;
     type->tt_args = NULL;
@@ -336,6 +353,29 @@
 }
 
 /*
+ * For a function type, reserve space for "argcount" argument types.
+ */
+    static int
+func_type_add_arg_types(
+	type_T	    *functype,
+	int	    argcount,
+	int	    min_argcount,
+	garray_T    *type_gap)
+{
+    if (ga_grow(type_gap, 1) == FAIL)
+	return FAIL;
+    functype->tt_args = ALLOC_CLEAR_MULT(type_T *, argcount);
+    if (functype->tt_args == NULL)
+	return FAIL;
+    ((type_T **)type_gap->ga_data)[type_gap->ga_len] = (void *)functype->tt_args;
+    ++type_gap->ga_len;
+
+    functype->tt_argcount = argcount;
+    functype->tt_min_argcount = min_argcount;
+    return OK;
+}
+
+/*
  * Return the type_T for a typval.  Only for primitive types.
  */
     static type_T *
@@ -810,12 +850,12 @@
  * Consumes "name".
  */
     static int
-generate_PUSHFUNC(cctx_T *cctx, char_u *name)
+generate_PUSHFUNC(cctx_T *cctx, char_u *name, type_T *type)
 {
     isn_T	*isn;
 
     RETURN_OK_IF_SKIP(cctx);
-    if ((isn = generate_instr_type(cctx, ISN_PUSHFUNC, &t_func_void)) == NULL)
+    if ((isn = generate_instr_type(cctx, ISN_PUSHFUNC, type)) == NULL)
 	return FAIL;
     isn->isn_arg.string = name;
 
@@ -1010,7 +1050,7 @@
     // drop the value types
     stack->ga_len -= count;
 
-    // Use the first value type for the list member type.  Use "void" for an
+    // Use the first value type for the list member type.  Use "any" for an
     // empty list.
     if (count > 0)
 	member = ((type_T **)stack->ga_data)[stack->ga_len];
@@ -1533,22 +1573,27 @@
 		*arg += len;
 		return &t_float;
 #else
-		emsg(_("E1055: This Vim is not compiled with float support"));
+		emsg(_("E1076: This Vim is not compiled with float support"));
 		return &t_any;
 #endif
 	    }
 	    if (len == 4 && STRNCMP(*arg, "func", len) == 0)
 	    {
 		type_T  *type;
-		type_T  *ret_type = &t_void;
+		type_T  *ret_type = &t_any;
 		int	argcount = -1;
 		int	flags = 0;
+		int	first_optional = -1;
 		type_T	*arg_type[MAX_FUNC_ARGS + 1];
 
 		// func({type}, ...): {type}
 		*arg += len;
 		if (**arg == '(')
 		{
+		    // "func" may or may not return a value, "func()" does
+		    // not return a value.
+		    ret_type = &t_void;
+
 		    p = ++*arg;
 		    argcount = 0;
 		    while (*p != NUL && *p != ')')
@@ -1560,6 +1605,18 @@
 			}
 			arg_type[argcount++] = parse_type(&p, type_gap);
 
+			if (*p == '?')
+			{
+			    if (first_optional == -1)
+				first_optional = argcount;
+			    ++p;
+			}
+			else if (first_optional != -1)
+			{
+			    emsg(_("E1007: mandatory argument after optional argument"));
+			    return &t_any;
+			}
+
 			if (*p != ',' && *skipwhite(p) == ',')
 			{
 			    semsg(_(e_no_white_before), ",");
@@ -1596,24 +1653,17 @@
 		    *arg = skipwhite(*arg);
 		    ret_type = parse_type(arg, type_gap);
 		}
-		type = get_func_type(ret_type, flags == 0 ? argcount : 99,
+		type = get_func_type(ret_type,
+			    flags == 0 && first_optional == -1 ? argcount : 99,
 								    type_gap);
 		if (flags != 0)
 		    type->tt_flags = flags;
 		if (argcount > 0)
 		{
-		    int type_ptr_cnt = (sizeof(type_T *) * argcount
-					+ sizeof(type_T) - 1) / sizeof(type_T);
-
-		    type->tt_argcount = argcount;
-		    // Get space from "type_gap" to avoid having to keep track
-		    // of the pointer and freeing it.
-		    ga_grow(type_gap, type_ptr_cnt);
-		    if (ga_grow(type_gap, type_ptr_cnt) == FAIL)
+		    if (func_type_add_arg_types(type, argcount,
+			    first_optional == -1 ? argcount : first_optional,
+							     type_gap) == FAIL)
 			return &t_any;
-		    type->tt_args =
-			     ((type_T **)type_gap->ga_data) + type_gap->ga_len;
-		    type_gap->ga_len += type_ptr_cnt;
 		    mch_memmove(type->tt_args, arg_type,
 						  sizeof(type_T *) * argcount);
 		}
@@ -1775,7 +1825,62 @@
 	    return *tofree;
 	}
     }
-    // TODO: function and partial argument types
+    if (type->tt_type == VAR_FUNC || type->tt_type == VAR_PARTIAL)
+    {
+	garray_T    ga;
+	int	    i;
+
+	ga_init2(&ga, 1, 100);
+	if (ga_grow(&ga, 20) == FAIL)
+	    return "[unknown]";
+	*tofree = ga.ga_data;
+	STRCPY(ga.ga_data, "func(");
+	ga.ga_len += 5;
+
+	for (i = 0; i < type->tt_argcount; ++i)
+	{
+	    char *arg_free;
+	    char *arg_type = type_name(type->tt_args[i], &arg_free);
+	    int  len;
+
+	    if (i > 0)
+	    {
+		STRCPY(ga.ga_data + ga.ga_len, ", ");
+		ga.ga_len += 2;
+	    }
+	    len = (int)STRLEN(arg_type);
+	    if (ga_grow(&ga, len + 6) == FAIL)
+	    {
+		vim_free(arg_free);
+		return "[unknown]";
+	    }
+	    *tofree = ga.ga_data;
+	    STRCPY(ga.ga_data + ga.ga_len, arg_type);
+	    ga.ga_len += len;
+	    vim_free(arg_free);
+	}
+
+	if (type->tt_member == &t_void)
+	    STRCPY(ga.ga_data + ga.ga_len, ")");
+	else
+	{
+	    char *ret_free;
+	    char *ret_name = type_name(type->tt_member, &ret_free);
+	    int  len;
+
+	    len = (int)STRLEN(ret_name) + 4;
+	    if (ga_grow(&ga, len) == FAIL)
+	    {
+		vim_free(ret_free);
+		return "[unknown]";
+	    }
+	    *tofree = ga.ga_data;
+	    STRCPY(ga.ga_data + ga.ga_len, "): ");
+	    STRCPY(ga.ga_data + ga.ga_len + 3, ret_name);
+	    vim_free(ret_free);
+	}
+	return ga.ga_data;
+    }
 
     return name;
 }
@@ -1868,7 +1973,9 @@
 }
 
 /*
- * Generate an instruction to load script-local variable "name".
+ * Generate an instruction to load script-local variable "name", without the
+ * leading "s:".
+ * Also finds imported variables.
  */
     static int
 compile_load_scriptvar(
@@ -1933,7 +2040,7 @@
 	}
 	else
 	{
-	    // TODO: check this is a variable, not a function
+	    // TODO: check this is a variable, not a function?
 	    generate_VIM9SCRIPT(cctx, ISN_LOADSCRIPT,
 		    import->imp_sid,
 		    import->imp_var_vals_idx,
@@ -1947,6 +2054,17 @@
     return FAIL;
 }
 
+    static int
+generate_funcref(cctx_T *cctx, char_u *name)
+{
+    ufunc_T *ufunc = find_func(name, cctx);
+
+    if (ufunc == NULL)
+	return FAIL;
+
+    return generate_PUSHFUNC(cctx, vim_strsave(name), ufunc->uf_func_type);
+}
+
 /*
  * Compile a variable name into a load instruction.
  * "end" points to just after the name.
@@ -2051,10 +2169,21 @@
 			|| (len == 5 && STRNCMP("false", *arg, 5) == 0))
 		    res = generate_PUSHBOOL(cctx, **arg == 't'
 						     ? VVAL_TRUE : VVAL_FALSE);
-		else if (SCRIPT_ITEM(current_sctx.sc_sid)->sn_version
-							== SCRIPT_VERSION_VIM9)
-		    // in Vim9 script "var" can be script-local.
-		   res = compile_load_scriptvar(cctx, name, *arg, &end, error);
+		else
+		{
+		    // "var" can be script-local even without using "s:" if it
+		    // already exists.
+		    if (SCRIPT_ITEM(current_sctx.sc_sid)->sn_version
+							== SCRIPT_VERSION_VIM9
+				|| lookup_script(*arg, len) == OK)
+		       res = compile_load_scriptvar(cctx, name, *arg, &end,
+									FALSE);
+
+		    // When the name starts with an uppercase letter or "x:" it
+		    // can be a user defined function.
+		    if (res == FAIL && (ASCII_ISUPPER(*name) || name[1] == ':'))
+			res = generate_funcref(cctx, name);
+		}
 	    }
 	}
 	if (gen_load)
@@ -2149,11 +2278,10 @@
 	// builtin function
 	idx = find_internal_func(name);
 	if (idx >= 0)
-	{
 	    res = generate_BCALL(cctx, idx, argcount);
-	    goto theend;
-	}
-	semsg(_(e_unknownfunc), namebuf);
+	else
+	    semsg(_(e_unknownfunc), namebuf);
+	goto theend;
     }
 
     // If we can find the function by name generate the right call.
@@ -2264,6 +2392,8 @@
     static int
 check_type(type_T *expected, type_T *actual, int give_msg)
 {
+    int ret = OK;
+
     if (expected->tt_type != VAR_UNKNOWN)
     {
 	if (expected->tt_type != actual->tt_type)
@@ -2274,17 +2404,21 @@
 	}
 	if (expected->tt_type == VAR_DICT || expected->tt_type == VAR_LIST)
 	{
-	    int ret;
-
 	    // void is used for an empty list or dict
-	    if (actual->tt_member == &t_void)
-		ret = OK;
-	    else
+	    if (actual->tt_member != &t_void)
 		ret = check_type(expected->tt_member, actual->tt_member, FALSE);
-	    if (ret == FAIL && give_msg)
-		type_mismatch(expected, actual);
-	    return ret;
 	}
+	else if (expected->tt_type == VAR_FUNC)
+	{
+	    if (expected->tt_member != &t_any)
+		ret = check_type(expected->tt_member, actual->tt_member, FALSE);
+	    if (ret == OK && expected->tt_argcount != -1
+		    && (actual->tt_argcount < expected->tt_min_argcount
+			|| actual->tt_argcount > expected->tt_argcount))
+		    ret = FAIL;
+	}
+	if (ret == FAIL && give_msg)
+	    type_mismatch(expected, actual);
     }
     return OK;
 }
@@ -2357,6 +2491,7 @@
     ufunc = rettv.vval.v_partial->pt_func;
     ++ufunc->uf_refcount;
     clear_tv(&rettv);
+    ga_init2(&ufunc->uf_type_list, sizeof(type_T *), 10);
 
     // The function will have one line: "return {expr}".
     // Compile it into instructions.
@@ -2401,6 +2536,7 @@
     ufunc = rettv.vval.v_partial->pt_func;
     ++ufunc->uf_refcount;
     clear_tv(&rettv);
+    ga_init2(&ufunc->uf_type_list, sizeof(type_T *), 10);
 
     // The function will have one line: "return {expr}".
     // Compile it into instructions.
@@ -3679,7 +3815,8 @@
 	    type = &t_string;
 	    if (is_decl)
 	    {
-		semsg(_("E1065: Cannot declare an environment variable: %s"), name);
+		semsg(_("E1065: Cannot declare an environment variable: %s"),
+									 name);
 		goto theend;
 	    }
 	}
@@ -3761,7 +3898,7 @@
 		if (is_decl)
 		{
 		    semsg(_("E1054: Variable already declared in the script: %s"),
-									     name);
+									 name);
 		    goto theend;
 		}
 	    }
@@ -3803,17 +3940,20 @@
 	goto theend;
     }
 
-    // +=, /=, etc. require an existing variable
     if (idx < 0 && dest == dest_local && cctx->ctx_skip != TRUE)
     {
 	if (oplen > 1 && !heredoc)
 	{
+	    // +=, /=, etc. require an existing variable
 	    semsg(_("E1020: cannot use an operator on a new variable: %s"),
 									 name);
 	    goto theend;
 	}
 
 	// new local variable
+	if ((type->tt_type == VAR_FUNC || type->tt_type == VAR_PARTIAL)
+					    && var_check_func_name(name, TRUE))
+	    goto theend;
 	idx = reserve_local(cctx, arg, varlen, cmdidx == CMD_const, type);
 	if (idx < 0)
 	    goto theend;
@@ -3897,7 +4037,7 @@
 	if (idx >= 0 && (is_decl || !has_type))
 	{
 	    lvar = ((lvar_T *)cctx->ctx_locals.ga_data) + idx;
-	    if (!has_type)
+	    if (new_local && !has_type)
 	    {
 		if (stacktype->tt_type == VAR_VOID)
 		{
@@ -3905,11 +4045,19 @@
 		    goto theend;
 		}
 		else
-		    lvar->lv_type = stacktype;
+		{
+		    // An empty list or dict has a &t_void member, for a
+		    // variable that implies &t_any.
+		    if (stacktype == &t_list_empty)
+			lvar->lv_type = &t_list_any;
+		    else if (stacktype == &t_dict_empty)
+			lvar->lv_type = &t_dict_any;
+		    else
+			lvar->lv_type = stacktype;
+		}
 	    }
-	    else
-		if (check_type(lvar->lv_type, stacktype, TRUE) == FAIL)
-		    goto theend;
+	    else if (check_type(lvar->lv_type, stacktype, TRUE) == FAIL)
+		goto theend;
 	}
 	else if (*p != '=' && check_type(type, stacktype, TRUE) == FAIL)
 	    goto theend;
@@ -3946,7 +4094,7 @@
 		generate_PUSHBLOB(cctx, NULL);
 		break;
 	    case VAR_FUNC:
-		generate_PUSHFUNC(cctx, NULL);
+		generate_PUSHFUNC(cctx, NULL, &t_func_void);
 		break;
 	    case VAR_PARTIAL:
 		generate_PUSHPARTIAL(cctx, NULL);
@@ -4039,7 +4187,24 @@
 		idx = get_script_item_idx(sid, rawname, TRUE);
 		// TODO: specific type
 		if (idx < 0)
-		    generate_OLDSCRIPT(cctx, ISN_STORES, name, sid, &t_any);
+		{
+		    char_u *name_s = name;
+
+		    // Include s: in the name for store_var()
+		    if (name[1] != ':')
+		    {
+			int len = (int)STRLEN(name) + 3;
+
+			name_s = alloc(len);
+			if (name_s == NULL)
+			    name_s = name;
+			else
+			    vim_snprintf((char *)name_s, len, "s:%s", name);
+		    }
+		    generate_OLDSCRIPT(cctx, ISN_STORES, name_s, sid, &t_any);
+		    if (name_s != name)
+			vim_free(name_s);
+		}
 		else
 		    generate_VIM9SCRIPT(cctx, ISN_STORESCRIPT,
 							     sid, idx, &t_any);
@@ -5357,13 +5522,17 @@
     {
 	int	is_ex_command;
 
+	// Bail out on the first error to avoid a flood of errors and report
+	// the right line number when inside try/catch.
+	if (emsg_before != called_emsg)
+	    goto erret;
+
 	if (line != NULL && *line == '|')
 	    // the line continues after a '|'
 	    ++line;
 	else if (line != NULL && *line != NUL)
 	{
-	    if (emsg_before == called_emsg)
-		semsg(_("E488: Trailing characters: %s"), line);
+	    semsg(_("E488: Trailing characters: %s"), line);
 	    goto erret;
 	}
 	else
@@ -5653,6 +5822,37 @@
 	dfunc->df_varcount = cctx.ctx_max_local;
     }
 
+    {
+	int argcount = ufunc->uf_args.ga_len
+					 + (ufunc->uf_va_name == NULL ? 0 : 1);
+
+	// Create a type for the function, with the return type and any
+	// argument types.
+	ufunc->uf_func_type = get_func_type(ufunc->uf_ret_type, argcount,
+							 &ufunc->uf_type_list);
+	if (argcount > 0)
+	{
+	    if (func_type_add_arg_types(ufunc->uf_func_type, argcount,
+			argcount - ufunc->uf_def_args.ga_len,
+						 &ufunc->uf_type_list) == FAIL)
+	    {
+		ret = FAIL;
+		goto erret;
+	    }
+	    if (ufunc->uf_arg_types == NULL)
+	    {
+		int i;
+
+		// lambda does not have argument types.
+		for (i = 0; i < argcount; ++i)
+		    ufunc->uf_func_type->tt_args[i] = &t_any;
+	    }
+	    else
+		mch_memmove(ufunc->uf_func_type->tt_args,
+			     ufunc->uf_arg_types, sizeof(type_T *) * argcount);
+	}
+    }
+
     ret = OK;
 
 erret:
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 54f95bf..237b024 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -377,7 +377,7 @@
     funccal_entry_T entry;
 
     save_funccal(&entry);
-    set_var_const(name, NULL, tv, FALSE, 0);
+    set_var_const(name, NULL, tv, FALSE, LET_NO_COMMAND);
     restore_funccal();
 }
 
@@ -739,7 +739,7 @@
 
 		    --ectx.ec_stack.ga_len;
 		    if (di == NULL)
-			store_var(iptr->isn_arg.string, STACK_TV_BOT(0));
+			store_var(name, STACK_TV_BOT(0));
 		    else
 		    {
 			clear_tv(&di->di_tv);
@@ -1828,7 +1828,7 @@
 					       iptr->isn_arg.loadstore.ls_sid);
 
 		    smsg("%4d LOADS s:%s from %s", current,
-					    iptr->isn_arg.string, si->sn_name);
+				 iptr->isn_arg.loadstore.ls_name, si->sn_name);
 		}
 		break;
 	    case ISN_LOADG:
@@ -1865,7 +1865,7 @@
 					       iptr->isn_arg.loadstore.ls_sid);
 
 		    smsg("%4d STORES %s in %s", current,
-					    iptr->isn_arg.string, si->sn_name);
+				 iptr->isn_arg.loadstore.ls_name, si->sn_name);
 		}
 		break;
 	    case ISN_STORESCRIPT: