expressions: Add closure expressions

blueprintcompiler/language/expression.py

@@ -64,6 +64,30 @@ class IdentExpr(AstNode):
         self.parent_by_type(Scope).variables[self.tokens["ident"]].emit_xml(xml)
 
 
+class ClosureExpr(AstNode):
+    grammar = [
+        UseIdent("function"),
+        "(",
+        Delimited(Expr, ",").expected("closure arguments"),
+        Match(")").expected(),
+    ]
+
+    @validate()
+    def is_cast_to_return_val(self):
+        if not isinstance(self.parent.parent, CastExpr):
+            raise CompileError(f"Closure expression needs to be cast to {self.tokens['function']}'s return type")
+
+    @property
+    def gir_type(self):
+        return self.parent.parent.gir_type
+
+    def emit_xml(self, xml: XmlEmitter):
+        xml.start_tag("closure", function=self.tokens["function"], type=self.gir_type)
+        for child in self.children[Expr]:
+            child.emit_xml(xml)
+        xml.end_tag()
+
+
 class LookupOp(InfixExpr):
     grammar = [".", UseIdent("property")]
 
@@ -92,6 +116,7 @@ class CastExpr(AstNode):
 
 
 expr.children = [
+    Prefix(ClosureExpr),
     Prefix(IdentExpr),
     Prefix(CastExpr),
     Prefix(["(", Expr, ")"]),

tests/sample_errors/closure_not_cast.blp

@@ -0,0 +1,5 @@
+using Gtk 4.0;
+
+Label {
+  label: bind my_func();
+}

tests/sample_errors/closure_not_cast.err

@@ -0,0 +1 @@
+4,15,9,Closure expression needs to be cast to my_func's return type

tests/samples/expr_closure.blp

@@ -0,0 +1,11 @@
+using Gtk 4.0;
+
+Box {
+  Box box {
+  }
+}
+
+Stack {
+  visible-child: bind ((Gtk.Button)my_closure(box.parent)).parent;
+  visible: bind (bool) my_other_closure(box);
+}

tests/samples/expr_closure.ui

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <requires lib="gtk" version="4.0"/>
+  <object class="GtkBox">
+    <child>
+      <object class="GtkBox" id="box"></object>
+    </child>
+  </object>
+  <object class="GtkStack">
+    <binding name="visible-child">
+      <lookup name="parent" type="GtkButton">
+        <closure function="my_closure" type="GtkButton">
+          <lookup name="parent">
+            <constant>box</constant>
+          </lookup>
+        </closure>
+      </lookup>
+    </binding>
+    <binding name="visible">
+      <closure function="my_other_closure" type="gboolean">
+        <constant>box</constant>
+      </closure>
+    </binding>
+  </object>
+</interface>

tests/test_samples.py

@@ -136,6 +136,7 @@ class TestSamples(unittest.TestCase):
         self.assert_sample("combo_box_text")
         self.assert_sample("comments")
         self.assert_sample("enum")
+        self.assert_sample("expr_closure")
         self.assert_sample("expr_lookup")
         self.assert_sample("file_filter")
         self.assert_sample("flags")
@@ -179,6 +180,7 @@ class TestSamples(unittest.TestCase):
         self.assert_sample_error("children")
         self.assert_sample_error("class_assign")
         self.assert_sample_error("class_dne")
+        self.assert_sample_error("closure_not_cast")
         self.assert_sample_error("consecutive_unexpected_tokens")
         self.assert_sample_error("does_not_implement")
         self.assert_sample_error("duplicate_obj_id")