checker: correct underline for unknown type in method type (#7223)

vlib/v/ast/ast.v

@@ -259,33 +259,34 @@ pub mut:
 
 pub struct FnDecl {
 pub:
-	name          string
-	mod           string
-	params        []table.Param
-	is_deprecated bool
-	is_pub        bool
-	is_variadic   bool
-	is_anon       bool
-	receiver      Field
-	receiver_pos  token.Position
-	is_method     bool
-	method_idx    int
-	rec_mut       bool // is receiver mutable
-	rec_share     table.ShareType
-	language      table.Language
-	no_body       bool // just a definition `fn C.malloc()`
-	is_builtin    bool // this function is defined in builtin/strconv
-	pos           token.Position
-	body_pos      token.Position
-	file          string
-	is_generic    bool
-	is_direct_arr bool // direct array access
-	attrs         []table.Attr
+	name            string
+	mod             string
+	params          []table.Param
+	is_deprecated   bool
+	is_pub          bool
+	is_variadic     bool
+	is_anon         bool
+	receiver        Field
+	receiver_pos    token.Position
+	is_method       bool
+	method_type_pos token.Position
+	method_idx      int
+	rec_mut         bool // is receiver mutable
+	rec_share       table.ShareType
+	language        table.Language
+	no_body         bool // just a definition `fn C.malloc()`
+	is_builtin      bool // this function is defined in builtin/strconv
+	pos             token.Position
+	body_pos        token.Position
+	file            string
+	is_generic      bool
+	is_direct_arr   bool // direct array access
+	attrs           []table.Attr
 pub mut:
-	stmts         []Stmt
-	return_type   table.Type
-	comments      []Comment // comments *after* the header, but *before* `{`; used for InterfaceDecl
-	source_file   &File = 0
+	stmts           []Stmt
+	return_type     table.Type
+	comments        []Comment // comments *after* the header, but *before* `{`; used for InterfaceDecl
+	source_file     &File = 0
 }
 
 // break, continue

vlib/v/checker/checker.v

@@ -4573,7 +4573,7 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 		for arg in node.params {
 			sym := c.table.get_type_symbol(arg.typ)
 			if sym.kind == .placeholder {
-				c.error('unknown type `$sym.name`', node.pos)
+				c.error('unknown type `$sym.name`', node.method_type_pos)
 			}
 		}
 	}

vlib/v/parser/fn.v

@@ -164,6 +164,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	mut rec_name := ''
 	mut is_method := false
 	mut receiver_pos := token.Position{}
+	mut rec_type_pos := token.Position{}
 	mut rec_type := table.void_type
 	mut rec_mut := false
 	mut params := []table.Param{}
@@ -194,7 +195,9 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		// }
 		// TODO: talk to alex, should mut be parsed with the type like this?
 		// or should it be a property of the arg, like this ptr/mut becomes indistinguishable
+		rec_type_pos = p.tok.position()
 		rec_type = p.parse_type_with_mut(rec_mut)
+		rec_type_pos = rec_type_pos.extend(p.prev_tok.position())
 		if is_amp && rec_mut {
 			p.error('use `(mut f Foo)` or `(f &Foo)` instead of `(mut f &Foo)`')
 			return ast.FnDecl{}
@@ -273,7 +276,8 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		// arrays/maps dont belong to a module only their element types do
 		// we could also check if kind is .array,  .array_fixed, .map instead of mod.len
 		if type_sym.mod.len > 0 && type_sym.mod != p.mod && type_sym.language == .v {
-			p.error('cannot define new methods on non-local type $type_sym.name')
+			p.error_with_pos('cannot define new methods on non-local type $type_sym.name',
+				rec_type_pos)
 			return ast.FnDecl{}
 		}
 		// p.warn('reg method $type_sym.name . $name ()')
@@ -346,6 +350,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		}
 		receiver_pos: receiver_pos
 		is_method: is_method
+		method_type_pos: rec_type_pos
 		method_idx: type_sym_method_idx
 		rec_mut: rec_mut
 		language: language