compiler: support shadowing via Block statements

pkg/compiler/codegen.go

@@ -890,6 +890,16 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 
 		return nil
 
+	case *ast.BlockStmt:
+		c.scope.vars.newScope()
+		defer c.scope.vars.dropScope()
+
+		for i := range n.List {
+			ast.Walk(c, n.List[i])
+		}
+
+		return nil
+
 	case *ast.ForStmt:
 		c.scope.vars.newScope()
 		defer c.scope.vars.dropScope()

pkg/compiler/global_test.go

@@ -81,4 +81,5 @@ func TestShadow(t *testing.T) {
 	t.Run("For", runCase("for i := 0; i < 1; i++ {"))
 	t.Run("Range", runCase("for range []int{1} {"))
 	t.Run("Switch", runCase("switch true {\ncase false: x += 2\ncase true:"))
+	t.Run("Block", runCase("{"))
 }