token: fix Token.str() for punctuation and operators (#8610)

vlib/v/parser/pratt.v

@@ -250,11 +250,11 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 					node = p.struct_init(true) // short_syntax: true
 				} else if p.tok.kind == .name {
 					p.next()
-					s := if p.tok.lit != '' { '`$p.tok.lit`' } else { p.tok.kind.str() }
-					p.error_with_pos('unexpected $s, expecting `:`', p.tok.position())
+					p.error_with_pos('unexpected $p.tok, expecting `:` after struct field name',
+						p.tok.position())
 					return ast.Expr{}
 				} else {
-					p.error_with_pos('unexpected `$p.tok.lit`, expecting struct key',
+					p.error_with_pos('unexpected $p.tok, expecting struct field name',
 						p.tok.position())
 					return ast.Expr{}
 				}

vlib/v/parser/tests/anon_fn_return_type.out

@@ -1,4 +1,4 @@
-vlib/v/parser/tests/anon_fn_return_type.vv:7:22: error: expected return type, not string "hi" for anonymous function
+vlib/v/parser/tests/anon_fn_return_type.vv:7:22: error: expected return type, not string `hi` for anonymous function
     5 | _ = fn (name string) flag.Flag
     6 | _ = fn (name string) flag.Flag {return {}}
     7 | _ = fn (name string) "hi" + name

vlib/v/parser/tests/struct_field_expected.out

@@ -0,0 +1,7 @@
+vlib/v/parser/tests/struct_field_expected.vv:6:2: error: unexpected `.`, expecting struct field name
+    4 | 
+    5 | x = {
+    6 |     .a : 'Alpha'
+      |     ^
+    7 |     .b : 'Beta'
+    8 | }

vlib/v/parser/tests/struct_field_expected.vv

@@ -0,0 +1,9 @@
+enum TestEnum {
+	a b
+}
+
+x = {
+	.a : 'Alpha'
+	.b : 'Beta'
+}
+

vlib/v/token/token.v

@@ -324,7 +324,16 @@ pub fn (t Kind) str() string {
 }
 
 pub fn (t Token) str() string {
-	return '$t.kind.str() "$t.lit"'
+	mut s := t.kind.str()
+	if s.len == 0 {
+		eprintln('missing token kind string')
+	} else if !s[0].is_letter() { 
+		// punctuation, operators
+		return '`$s`' 
+	}
+	// string contents etc
+	if t.lit != '' { s += ' `$t.lit`' }
+	return s
 }
 
 // Representation of highest and lowest precedence