parser: fix imported interfaces

vlib/v/checker/checker.v

@@ -50,7 +50,7 @@ pub fn new_checker(table &table.Table, pref &pref.Preferences) Checker {
 pub fn (mut c Checker) check(ast_file ast.File) {
 	c.file = ast_file
 	for i, ast_import in ast_file.imports {
-		for j in 0..i {
+		for j in 0 .. i {
 			if ast_import.mod == ast_file.imports[j].mod {
 				c.error('module name `$ast_import.mod` duplicate', ast_import.pos)
 			}
@@ -976,7 +976,7 @@ pub fn (mut c Checker) return_stmt(return_stmt mut ast.Return) {
 
 pub fn (mut c Checker) enum_decl(decl ast.EnumDecl) {
 	for i, field in decl.fields {
-		for j in 0..i {
+		for j in 0 .. i {
 			if field.name == decl.fields[j].name {
 				c.error('field name `$field.name` duplicate', field.pos)
 			}
@@ -1439,7 +1439,9 @@ fn (mut c Checker) stmt(node ast.Stmt) {
 }
 
 fn (mut c Checker) stmts(stmts []ast.Stmt) {
-	mut unreachable := token.Position{line_nr: -1}
+	mut unreachable := token.Position{
+		line_nr: -1
+	}
 	c.expected_type = table.void_type
 	for stmt in stmts {
 		if c.scope_returns {
@@ -1877,7 +1879,8 @@ pub fn (mut c Checker) if_expr(node mut ast.IfExpr) table.Type {
 					// p.warn('if expr ret $type_sym.name')
 					t := c.expr(it.expr)
 					if is_ternary && t != first_typ {
-						c.error('mismatched types `${c.table.type_to_str(first_typ)}` and `${c.table.type_to_str(t)}`', node.pos)
+						c.error('mismatched types `${c.table.type_to_str(first_typ)}` and `${c.table.type_to_str(t)}`',
+							node.pos)
 					}
 					node.typ = t
 					return t

vlib/v/parser/struct.v

@@ -257,7 +257,7 @@ fn (mut p Parser) interface_decl() ast.InterfaceDecl {
 		p.next()
 	}
 	p.next() // `interface`
-	interface_name := p.check_name()
+	interface_name := p.prepend_mod(p.check_name())
 	// println('interface decl $interface_name')
 	p.check(.lcbr)
 	// Declare the type

vlib/v/tests/interface_test.v

@@ -1,3 +1,4 @@
+
 struct Dog {
 	breed string
 }
@@ -28,10 +29,6 @@ fn test_todo() {
 	else{}
 }
 
-interface Speaker {
-	name() string
-	speak()
-}
 
 fn perform_speak(s Speaker) {
 	s.speak()
@@ -86,3 +83,8 @@ struct Foo {
 	speakers []Speaker
 }
 
+interface Speaker {
+	name() string
+	speak()
+}
+