checker: add details about a non matching functional argument

vlib/v/builder/builder.v

@@ -235,6 +235,9 @@ fn (b &Builder) print_warnings_and_errors() {
 			kind := if b.pref.is_verbose { '$err.reporter warning #$b.checker.nr_warnings:' } else { 'warning:' }
 			ferror := util.formatted_error(kind, err.message, err.file_path, err.pos)
 			eprintln(ferror)
+			if err.details.len > 0 {
+				eprintln('details: $err.details')
+			}                
 			// eprintln('')
 			if i > b.max_nr_errors {
 				return
@@ -250,6 +253,9 @@ fn (b &Builder) print_warnings_and_errors() {
 			kind := if b.pref.is_verbose { '$err.reporter error #$b.checker.nr_errors:' } else { 'error:' }
 			ferror := util.formatted_error(kind, err.message, err.file_path, err.pos)
 			eprintln(ferror)
+			if err.details.len > 0 {
+				eprintln('details: $err.details')
+			}                
 			// eprintln('')
 			if i > b.max_nr_errors {
 				return

vlib/v/checker/check_types.v

@@ -143,11 +143,9 @@ pub fn (c &Checker) check_matching_function_symbols(got_type_sym &table.TypeSymb
 		exp_arg_is_ptr := exp_arg.typ.is_ptr() || exp_arg.typ.is_pointer()
 		got_arg_is_ptr := got_arg.typ.is_ptr() || got_arg.typ.is_pointer()
 		if exp_arg_is_ptr != got_arg_is_ptr {
-			$if debug_matching_function_symbols ? {
+			exp_arg_pointedness := if exp_arg_is_ptr { 'a pointer' } else { 'NOT a pointer' }
-				exp_arg_pointedness := if exp_arg_is_ptr { 'a pointer' } else { 'NOT a pointer' }
+			got_arg_pointedness := if got_arg_is_ptr { 'a pointer' } else { 'NOT a pointer' }
-				got_arg_pointedness := if got_arg_is_ptr { 'a pointer' } else { 'NOT a pointer' }
+			c.add_error_detail('`$exp_fn.name`\'s expected fn argument: `$exp_arg.name` is $exp_arg_pointedness, but the passed fn argument: `$got_arg.name` is $got_arg_pointedness')
-				eprintln('`$exp_fn.name` expected fn argument: `$exp_arg.name` is $exp_arg_pointedness, but `$got_fn.name` actual fn argument: `$got_arg.name` is $got_arg_pointedness')
-			}
 			return false
 		}
 		if !c.check_basic(got_arg.typ, exp_arg.typ) {

vlib/v/checker/checker.v

@@ -43,6 +43,7 @@ mut:
 	expr_level       int // to avoid infinit recursion segfaults due to compiler bugs
 	inside_sql       bool // to handle sql table fields pseudo variables
 	cur_orm_ts       table.TypeSymbol
+	error_details    []string
 }
 
 pub fn new_checker(table &table.Table, pref &pref.Preferences) Checker {
@@ -2812,6 +2813,10 @@ pub fn (mut c Checker) map_init(mut node ast.MapInit) table.Type {
 	return map_type
 }
 
+pub fn (mut c Checker) add_error_detail(s string) {
+	c.error_details << s
+}
+
 pub fn (mut c Checker) warn(s string, pos token.Position) {
 	allow_warnings := !c.pref.is_prod // allow warnings only in dev builds
 	c.warn_or_error(s, pos, allow_warnings) // allow warnings only in dev builds
@@ -2829,6 +2834,11 @@ fn (mut c Checker) warn_or_error(message string, pos token.Position, warn bool)
 	// if c.pref.is_verbose {
 	// print_backtrace()
 	// }
+	mut details := ''
+	if c.error_details.len > 0 { 
+		details = c.error_details.join('\n')
+		c.error_details = []        
+	}
 	if warn && !c.pref.skip_warnings {
 		c.nr_warnings++
 		wrn := errors.Warning{
@@ -2836,6 +2846,7 @@ fn (mut c Checker) warn_or_error(message string, pos token.Position, warn bool)
 			pos: pos
 			file_path: c.file.path
 			message: message
+			details: details
 		}
 		c.file.warnings << wrn
 		c.warnings << wrn
@@ -2849,6 +2860,7 @@ fn (mut c Checker) warn_or_error(message string, pos token.Position, warn bool)
 				pos: pos
 				file_path: c.file.path
 				message: message
+				details: details
 			}
 			c.file.errors << err
 			c.errors << err

vlib/v/checker/tests/non_matching_functional_args.out

@@ -5,6 +5,7 @@ vlib/v/checker/tests/non_matching_functional_args.v:27:2: error: cannot use anon
       |     ~~~~~~~~~~~~~~~~~~~~~~
    28 |         t.rename()
    29 |         println(t.name)
+details: `main.MyFn`'s expected fn argument: `zzzz` is NOT a pointer, but the passed fn argument: `t` is a pointer
 vlib/v/checker/tests/non_matching_functional_args.v:31:2: error: cannot use fn `xxx` as function type `MyFn` in argument 1 to `sum` 
    29 |         println(t.name)
    30 |     })
@@ -12,3 +13,4 @@ vlib/v/checker/tests/non_matching_functional_args.v:31:2: error: cannot use fn `
       |     ~~~~~~~~
    32 |     sum(yyy)
    33 | }
+details: `main.MyFn`'s expected fn argument: `zzzz` is NOT a pointer, but the passed fn argument: `mytable` is a pointer

vlib/v/checker/tests/non_matching_functional_args.vv

@@ -13,9 +13,9 @@ fn yyy(t Table) {
 	println(t.name)
 }
 
-fn xxx(mut t Table) {
+fn xxx(mut mytable Table) {
-	t.rename()
+	mytable.rename()
-	println(t.name)
+	println(mytable.name)
 }
 
 fn sum(myfn MyFn) {

vlib/v/errors/errors.v

@@ -12,6 +12,7 @@ pub enum Reporter {
 pub struct Error {
 pub:
 	message   string
+	details string
 	file_path string
 	pos       token.Position
 	backtrace string
@@ -21,6 +22,7 @@ pub:
 pub struct Warning {
 pub:
 	message   string
+	details   string
 	file_path string
 	pos       token.Position
 	reporter  Reporter