fmt: interface decl fixes (#5829)

vlib/v/ast/ast.v

@@ -179,6 +179,7 @@ pub struct InterfaceDecl {
 pub:
 	name        string
 	field_names []string
+	is_pub      bool
 	methods     []FnDecl
 	pos         token.Position
 }

vlib/v/fmt/fmt.v

@@ -428,12 +428,7 @@ pub fn (mut f Fmt) stmt(node ast.Stmt) {
 			// f.imports(f.file.imports)
 		}
 		ast.InterfaceDecl {
-			f.writeln('interface $it.name {')
+			f.interface_decl(it)
-			for method in it.methods {
-				f.write('\t')
-				f.writeln(method.stringify(f.table, f.cur_mod).after('fn '))
-			}
-			f.writeln('}\n')
 		}
 		ast.Module {
 			f.mod(it)
@@ -662,6 +657,19 @@ pub fn (mut f Fmt) struct_decl(node ast.StructDecl) {
 	f.writeln('}\n')
 }
 
+pub fn (mut f Fmt) interface_decl(node ast.InterfaceDecl) {
+	if node.is_pub {
+		f.write('pub ')
+	}
+	name := node.name.after('.')
+	f.writeln('interface $name {')
+	for method in node.methods {
+		f.write('\t')
+		f.writeln(method.stringify(f.table, f.cur_mod).after('fn '))
+	}
+	f.writeln('}\n')
+}
+
 pub fn (mut f Fmt) prefix_expr_cast_expr(fexpr ast.Expr) {
 	mut is_pe_amp_ce := false
 	mut ce := ast.CastExpr{}
@@ -1053,7 +1061,7 @@ pub fn (mut f Fmt) expr(node ast.Expr) {
 		}
 		ast.UnsafeExpr {
 			f.writeln('unsafe {')
-			f.stmts(it.stmts)
+			f.stmts(node.stmts)
 			f.writeln('}')
 		}
 	}

vlib/v/fmt/tests/module_interface_keep.vv

@@ -0,0 +1,5 @@
+module module_fmt
+
+pub interface MyInterface {
+	fun()
+}

vlib/v/parser/struct.v

@@ -396,6 +396,7 @@ fn (mut p Parser) interface_decl() ast.InterfaceDecl {
 	return ast.InterfaceDecl{
 		name: interface_name
 		methods: methods
+		is_pub: is_pub
 		pos: start_pos
 	}
 }