parser: small fixes to make silent mod work with example/json (#7246)

.github/workflows/ci.yml

@@ -610,3 +610,4 @@ jobs:
         ./v test-parser examples/hanoi.v
         ./v test-parser examples/fibonacci.v
         ./v test-parser examples/cli.v
+        ./v test-parser examples/json.v

vlib/v/checker/checker.v

@@ -264,7 +264,7 @@ fn (mut c Checker) check_file_in_main(file ast.File) bool {
 }
 
 fn (mut c Checker) check_valid_snake_case(name string, identifier string, pos token.Position) {
-	if !c.pref.is_vweb && (name[0] == `_` || name.contains('._')) {
+	if !c.pref.is_vweb && name.len > 0 && (name[0] == `_` || name.contains('._')) {
 		c.error('$identifier `$name` cannot start with `_`', pos)
 	}
 	if !c.pref.experimental && !c.pref.translated && util.contains_capital(name) {
@@ -280,7 +280,7 @@ fn stripped_name(name string) string {
 
 fn (mut c Checker) check_valid_pascal_case(name string, identifier string, pos token.Position) {
 	sname := stripped_name(name)
-	if !sname[0].is_capital() && !c.pref.translated {
+	if sname.len > 0 && !sname[0].is_capital() && !c.pref.translated {
 		c.error('$identifier `$name` must begin with capital letter', pos)
 	}
 }
@@ -1391,7 +1391,7 @@ pub fn (mut c Checker) call_fn(mut call_expr ast.CallExpr) table.Type {
 	// println(fn_name)
 	// }
 	if fn_name == 'json.encode' {
-	} else if fn_name == 'json.decode' {
+	} else if fn_name == 'json.decode' && call_expr.args.len > 0 {
 		expr := call_expr.args[0].expr
 		if expr !is ast.Type {
 			typ := typeof(expr)

vlib/v/parser/fn.v

@@ -199,6 +199,10 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		// 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)
+		if rec_type.idx() == 0 {
+			// error is set in parse_type
+			return ast.FnDecl{}
+		}
 		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)`')

vlib/v/parser/parse_type.v

@@ -21,6 +21,10 @@ pub fn (mut p Parser) parse_array_type() table.Type {
 	// array
 	p.check(.rsbr)
 	elem_type := p.parse_type()
+	if elem_type.idx() == 0 {
+		// error is set in parse_type
+		return 0
+	}
 	mut nr_dims := 1
 	// detect attr
 	not_attr := p.peek_tok.kind != .name && p.peek_tok2.kind !in [.semicolon, .rsbr]
@@ -165,6 +169,10 @@ pub fn (mut p Parser) parse_type() table.Type {
 	if p.tok.kind != .lcbr {
 		pos := p.tok.position()
 		typ = p.parse_any_type(language, nr_muls > 0, true)
+		if typ.idx() == 0 {
+			// error is set in parse_type
+			return 0
+		}
 		if typ == table.void_type {
 			p.error_with_pos('use `?` instead of `?void`', pos)
 			return 0

vlib/v/parser/struct.v

@@ -194,6 +194,10 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 					}
 				}
 				typ = p.parse_type()
+				if typ.idx() == 0 {
+					// error is set in parse_type
+					return ast.StructDecl{}
+				}
 				type_pos = p.prev_tok.position()
 				field_pos = field_start_pos.extend(type_pos)
 			}