checker: fix error position for assignment expression

vlib/v/checker/checker.v

@@ -215,7 +215,7 @@ fn (c mut Checker) assign_expr(assign_expr mut ast.AssignExpr) {
 	if !c.table.check(right_type, left_type) {
 		left_type_sym := c.table.get_type_symbol(left_type)
 		right_type_sym := c.table.get_type_symbol(right_type)
-		c.error('cannot assign `$right_type_sym.name` to `$left_type_sym.name`', assign_expr.pos)
+		c.error('cannot assign `$right_type_sym.name` to variable `${assign_expr.left.str()}` of type `$left_type_sym.name` ', assign_expr.pos)
 	}
 	c.check_expr_opt_call(assign_expr.val, right_type, true)
 }

vlib/v/checker/tests/inout/void_function_assign_to_string.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/inout/void_function_assign_to_string.v:6:6: error: cannot assign `void` to variable `a` of type `string`  
+    4| fn main(){
+    5|     mut a := ''
+    6|     a = x(1,2) // hello
+               ^
+    7|     eprintln('a: $a')
+    8| }

vlib/v/checker/tests/inout/void_function_assign_to_string.vv

@@ -0,0 +1,8 @@
+fn x(x,y int) {
+
+}
+fn main(){
+	mut a := ''
+	a = x(1,2) // hello
+	eprintln('a: $a')
+}

vlib/v/parser/parser.v

@@ -461,6 +461,7 @@ pub fn (p mut Parser) stmt() ast.Stmt {
 pub fn (p mut Parser) assign_expr(left ast.Expr) ast.AssignExpr {
 	op := p.tok.kind
 	p.next()
+	pos := p.tok.position()
 	val := p.expr(0)
 	match left {
 		ast.IndexExpr {
@@ -473,7 +474,7 @@ pub fn (p mut Parser) assign_expr(left ast.Expr) ast.AssignExpr {
 		left: left
 		val: val
 		op: op
-		pos: p.tok.position()
+		pos: pos
 	}
 	return node
 }

vlib/v/util/errors.v

@@ -95,8 +95,12 @@ pub fn formatted_error(kind string /*error or warn*/, emsg string, filepath stri
 					}
 					continue
 				}
-				underline := '~'.repeat(pos.len)
-				pointerline << if emanager.support_color { term.bold(term.blue(underline)) } else { underline }
+				if pos.len > 1 {
+					underline := '~'.repeat(pos.len)
+					pointerline << if emanager.support_color { term.bold(term.blue(underline)) } else { underline }
+				}else{
+					pointerline << if emanager.support_color { term.bold(term.blue('^')) } else { '^' }
+				}
 				break
 			}
 			clines << '       ' + pointerline.join('')