parser: fix fn argument type position (#15102)

vlib/v/checker/tests/array_sort_with_compare_ref_elem_err.out

@@ -2,6 +2,6 @@ vlib/v/checker/tests/array_sort_with_compare_ref_elem_err.vv:21:23: error: sort_
    19 | }
    20 |
    21 | fn sort_cells_by_yx(a &Cell, b &Cell) int {
-      |                       ^
+      |                       ~~~~~
    22 |     if a.pos.y == b.pos.y {
    23 |         if a.pos.x < b.pos.x {

vlib/v/checker/tests/fn_arg_of_optional_err.out

@@ -1,5 +1,5 @@
 vlib/v/checker/tests/fn_arg_of_optional_err.vv:1:19: error: optional type argument is not supported currently
     1 | fn optional_arg(x ?int) {
-      |                   ^
+      |                   ~~~~
     2 |     println('int type: $x')
     3 | }

vlib/v/checker/tests/private_redeclaration_of_C_struct.out

@@ -1,26 +1,26 @@
 vlib/sokol/audio/audio.v:86:26: error: struct `C.saudio_desc` was declared as private to module `module_with_redeclaration`, so it can not be used inside module `sokol.audio`
    84 | fn C.saudio_userdata() voidptr
-   85 | 
+   85 |
    86 | fn C.saudio_query_desc() C.saudio_desc
       |                          ~~~~~~~~~~~~~
-   87 | 
+   87 |
    88 | fn C.saudio_sample_rate() int
 vlib/sokol/audio/audio.v:101:19: error: struct `C.saudio_desc` was declared as private to module `module_with_redeclaration`, so it can not be used inside module `sokol.audio`
-   99 | 
+   99 |
   100 | // setup - setup sokol-audio
   101 | pub fn setup(desc &C.saudio_desc) {
-      |                   ^
+      |                   ~~~~~~~~~~~~~~
   102 |     C.saudio_setup(desc)
   103 | }
 vlib/sokol/audio/audio.v:121:16: error: struct `C.saudio_desc` was declared as private to module `module_with_redeclaration`, so it can not be used inside module `sokol.audio`
-  119 | 
+  119 |
   120 | // query - return a copy of the original saudio_desc struct
   121 | pub fn query() C.saudio_desc {
       |                ~~~~~~~~~~~~~
   122 |     return C.saudio_query_desc()
   123 | }
 vlib/v/checker/tests/private_redeclaration_of_C_struct.vv:7:10: error: struct `C.saudio_desc` was declared as private to module `module_with_redeclaration`, so it can not be used inside module `main`
-    5 | 
+    5 |
     6 | fn main() {
     7 |     sd := C.saudio_desc{}
       |             ~~~~~~~~~~~~~

vlib/v/parser/fn.v

@@ -830,6 +830,7 @@ fn (mut p Parser) fn_args() ([]ast.Param, bool, bool) {
 			}
 			pos := p.tok.pos()
 			mut arg_type := p.parse_type()
+			type_pos := pos.extend(p.prev_tok.pos())
 			if arg_type == 0 {
 				// error is added in parse_type
 				return []ast.Param{}, false, false
@@ -884,7 +885,7 @@ fn (mut p Parser) fn_args() ([]ast.Param, bool, bool) {
 				name: name
 				is_mut: is_mut
 				typ: arg_type
-				type_pos: pos
+				type_pos: type_pos
 			}
 			arg_no++
 			if arg_no > 1024 {
@@ -940,6 +941,7 @@ fn (mut p Parser) fn_args() ([]ast.Param, bool, bool) {
 			}
 			pos := p.tok.pos()
 			mut typ := p.parse_type()
+			type_pos[0] = pos.extend(p.prev_tok.pos())
 			if typ == 0 {
 				// error is added in parse_type
 				return []ast.Param{}, false, false