checker: add a suggestion for misspelled field names in struct literals

vlib/v/checker/struct.v

@@ -3,6 +3,7 @@
 module checker
 
 import v.ast
+import v.util
 
 pub fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 	mut struct_sym, struct_typ_idx := c.table.find_sym_and_type_idx(node.name)
@@ -391,7 +392,8 @@ pub fn (mut c Checker) struct_init(mut node ast.StructInit) ast.Type {
 						ast.StructField{}
 					}
 					if !exists {
-						c.error('unknown field `$field.name` in struct literal of type `$type_sym.name`',
+						existing_fields := c.table.struct_fields(type_sym).map(it.name)
+						c.error(util.new_suggestion(field.name, existing_fields).say('unknown field `$field.name` in struct literal of type `$type_sym.name`'),
 							field.pos)
 						continue
 					}

vlib/v/checker/tests/struct_unknown_field.out

@@ -1,4 +1,5 @@
-vlib/v/checker/tests/struct_unknown_field.vv:8:3: error: unknown field `bar` in struct literal of type `Test`
+vlib/v/checker/tests/struct_unknown_field.vv:8:3: error: unknown field `bar` in struct literal of type `Test`.
+1 possibility: `foo`.
     6 |     t := Test{
     7 |         foo: true
     8 |         bar: false

vlib/v/checker/tests/unknown_field_in_struct_literal.out

@@ -0,0 +1,8 @@
+vlib/v/checker/tests/unknown_field_in_struct_literal.vv:10:2: error: unknown field `pos` in struct literal of type `TileLine`.
+Did you mean `ypos`?
+    8 | 
+    9 | hline := TileLine{
+   10 |     pos: 123
+      |     ~~~~~~~~
+   11 | }
+   12 | println(hline)

vlib/v/checker/tests/unknown_field_in_struct_literal.vv

@@ -0,0 +1,12 @@
+struct TileLine {
+	ypos int
+mut:
+	field  [5]int
+	points int
+	shifts int
+}
+
+hline := TileLine{
+	pos: 123
+}
+println(hline)