feat(compiler): interface declaration (#1938)

This PR adds support for `interface` according to the [spec](https://docs.winglang.io/reference/spec#34-interfaces). Also in this PR: - [x] Removed interface fields from the spec and our codebase ([slack discussion](https://winglang.slack.com/archives/C048QCN2XLJ/p1680077416200329)). - [x] Removed access modifiers from interface methods (to comply with the spec). - [x] (Very) small refactoring in our grammar.js to rename method return type from `type` to `return_type`. - [x] Removed unused parameter `is_class` from SymbolEnv::new Fixes #123 *By submitting this pull request, I confirm that my contribution is made under the terms of the [Monada Contribution License](https://docs.winglang.io/terms-and-policies/contribution-license.html)*.
winglang · Apr 2, 2023 · 7e12b93 · 7e12b93
1 parent 346dca1
commit 7e12b93
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diff --git a/docs/04-reference/winglang-spec.md b/docs/04-reference/winglang-spec.md
@@ -1647,22 +1647,24 @@ separated with commas.
 All methods of an interface are implicitly public and cannot be of any other
 type of visibility (private, protected, etc.).
 
+Interface fields are not supported.
+
 > ```TS
 > // Wing program:
 > interface IMyInterface1 {
->   field1: num;
 >   method1(x: num): str;
 > };
 > interface IMyInterface2 {
->   inflight field2: str;
 >   inflight method2(): str;
 > };
 > resource MyResource impl IMyInterface1, IMyInterface2 {
->   inflight field2: str;
+>   field1: num;
+>   field2: str;
+>
 >   inflight init(x: num) {
 >     // inflight client initialization
->     this.field2 = "sample";
 >     this.field1 = x;
+>     this.field2 = "sample";
 >   }
 >   method1(x: num): str {
 >     return "sample: ${x}";

diff --git a/examples/tests/invalid/impl_interface.w b/examples/tests/invalid/impl_interface.w
@@ -17,3 +17,22 @@ resource C impl cloud.Bucket {
               // ^^^^^^^^^^^ Error: cloud.Bucket is a resource, not an interface
   init() {}
 }
+
+interface I1 {
+  method_1(x: num): num;
+}
+
+interface I2 extends I1 {
+  inflight method_2(x: str): str;
+}
+
+interface I3 extends I2 {
+  method_3(x: Array<num>): Array<num>;
+}
+
+resource r impl I3 {
+      // ^ Resource "r" does not implement method "method_1" of interface "I3"
+      // ^ Resource "r" does not implement method "method_2" of interface "I3"
+      // ^ Resource "r" does not implement method "method_3" of interface "I3"
+  init() {}
+}
diff --git a/examples/tests/invalid/interface.w b/examples/tests/invalid/interface.w
@@ -0,0 +1,29 @@
+// interface extend loop
+interface IA extends IB {
+                  // ^^ Unknown symbol "IB"
+}
+
+interface IB extends IA {
+}
+
+// interface extends interface which doesn't exist
+interface IExist extends IDontExist {
+                      // ^^^^^^^^^^ Unknown symbol "IDontExist"
+}
+
+// interface extends class
+class ISomeClass {
+    init(){}
+}
+interface ISomeInterface extends ISomeClass {
+                      // Interface "ISomeInterface (at ../../examples/tests/invalid/interface.w:21:11)" extends "ISomeClass", which is not an interface
+}
+
+// interface with multiple methods having the same name, different signature
+interface IWithSameName {
+    foo();
+    foo();
+ // ^^^ Symbol "foo" already defined in this scope
+    foo(): num;
+ // ^^^ Symbol "foo" already defined in this scope
+}
diff --git a/examples/tests/valid/impl_interface.w b/examples/tests/valid/impl_interface.w
@@ -12,3 +12,42 @@ let x: cloud.IQueueOnMessageHandler = new A();
 let y = inflight () => {
   x.handle("hello world!");
 };
+
+interface I1 {
+  method_1(x: num): num;
+}
+
+interface I2 extends I1 {
+  inflight method_2(x: str): str;
+}
+
+interface I3 extends I2 {
+  method_3(x: Array<num>): Array<num>;
+}
+
+resource r impl I3 {
+  init() {}
+  method_1(x: num): num {
+    return x;
+  }
+  inflight method_2(x: str): str {
+    return x;
+  }
+  method_3(x: Array<num>): Array<num> {
+    return x;
+  }
+}
+
+// a variable of some interface type can be assigned a class instance that implements it.
+interface IAnimal {
+  inflight eat();
+}
+
+resource Dog impl IAnimal {
+  init(){}
+  inflight eat() {
+    return;
+  }
+}
+
+let z: IAnimal = new Dog();
diff --git a/examples/tests/valid/interface.w b/examples/tests/valid/interface.w
@@ -0,0 +1,16 @@
+interface IShape {
+    // method with a return type
+    method_1(): str;
+    // method without a return type
+    method_2();
+    // method with a return type of the interface type
+    method_3(): IShape;
+}
+
+interface IPointy {
+    method_2();
+}
+
+interface ISquare extends IShape, IPointy {
+
+}
diff --git a/libs/tree-sitter-wing/grammar.js b/libs/tree-sitter-wing/grammar.js
@@ -210,7 +210,7 @@ module.exports = grammar({
       seq(
         "interface",
         field("name", $.identifier),
-        optional(seq("extends", field("implements", commaSep1($.custom_type)))),
+        optional(seq("extends", field("extends", commaSep1($.custom_type)))),
         field("implementation", $.interface_implementation)
       ),
     interface_implementation: ($) =>
@@ -415,14 +415,14 @@ module.exports = grammar({
 
     extern_modifier : ($) => seq("extern", $.string),
 
+    _return_type: ($) => $._type_annotation,
+
     method_signature: ($) =>
       seq(
-        optional(field("access_modifier", $.access_modifier)),
-        optional(field("static", $.static)),
         optional(field("async", $.async_modifier)),
         field("name", $.identifier),
         field("parameter_list", $.parameter_list),
-        optional(field("return_type", $._type_annotation)),
+        optional($._return_type),
         ";"
       ),
 
@@ -434,18 +434,16 @@ module.exports = grammar({
         optional(field("async", $.async_modifier)),
         field("name", $.identifier),
         field("parameter_list", $.parameter_list),
-        optional(field("return_type", $._type_annotation)),
+        optional($._return_type),
         choice(field("block", $.block), ";")
       ),
 
     inflight_method_signature: ($) =>
       seq(
-        optional(field("access_modifier", $.access_modifier)),
-        optional(field("static", $.static)),
         field("phase_modifier", $._inflight_specifier),
         field("name", $.identifier),
         field("parameter_list", $.parameter_list),
-        optional(field("return_type", $._type_annotation)),
+        optional($._return_type),
         ";"
       ),
 
@@ -457,7 +455,7 @@ module.exports = grammar({
         field("phase_modifier", $._inflight_specifier),
         field("name", $.identifier),
         field("parameter_list", $.parameter_list),
-        optional(field("return_type", $._type_annotation)),
+        optional($._return_type),
         choice(field("block", $.block), ";")
       ),
 
@@ -557,7 +555,7 @@ module.exports = grammar({
     preflight_closure: ($) =>
       seq(
         field("parameter_list", $.parameter_list),
-        optional(field("return_type", $._type_annotation)),
+        optional($._return_type),
         "=>",
         field("block", $.block)
       ),
@@ -566,7 +564,7 @@ module.exports = grammar({
       seq(
         "inflight",
         field("parameter_list", $.parameter_list),
-        optional(field("return_type", $._type_annotation)),
+        optional($._return_type),
         "=>",
         field("block", $.block)
       ),

diff --git a/libs/tree-sitter-wing/test/corpus/statements/class_and_resource.txt b/libs/tree-sitter-wing/test/corpus/statements/class_and_resource.txt
@@ -82,7 +82,7 @@ resource A {
     async preflight_func() {}
     public preflight_func2() {}
     inflight inflight_func() {}
-    public inflight inflight_func2() {}
+    public inflight inflight_func2(): num {}
     pf_member: str;
     inflight if_member: str;
     public inflight var if_member2: str;
@@ -124,6 +124,7 @@ resource A {
                 access_modifier: (access_modifier)
                 name: (identifier)
                 parameter_list: (parameter_list)
+                type: (builtin_type)
                 block: (block)
             )
             (class_field
@@ -193,9 +194,9 @@ interface A extends B, C {
 (source
   (interface_definition
     name: (identifier)
-    implements: (custom_type
+    extends: (custom_type
       object: (identifier))
-    implements: (custom_type
+    extends: (custom_type
       object: (identifier))
     implementation: (interface_implementation
       (method_signature

diff --git a/libs/wingc/src/ast.rs b/libs/wingc/src/ast.rs
@@ -265,6 +265,13 @@ pub struct Class {
 	pub is_resource: bool,
 }
 
+#[derive(Debug)]
+pub struct Interface {
+	pub name: Symbol,
+	pub methods: Vec<(Symbol, FunctionSignature)>,
+	pub extends: Vec<UserDefinedType>,
+}
+
 #[derive(Debug)]
 pub enum StmtKind {
 	Bring {
@@ -302,6 +309,7 @@ pub enum StmtKind {
 	Return(Option<Expr>),
 	Scope(Scope),
 	Class(Class),
+	Interface(Interface),
 	Struct {
 		name: Symbol,
 		extends: Vec<Symbol>,

diff --git a/libs/wingc/src/capture.rs b/libs/wingc/src/capture.rs
@@ -399,7 +399,11 @@ fn scan_captures_in_inflight_scope(scope: &Scope, diagnostics: &mut Diagnostics)
 				todo!()
 			}
 			// Type definitions with no expressions in them can't capture anything
-			StmtKind::Struct { .. } | StmtKind::Enum { .. } | StmtKind::Break | StmtKind::Continue => {}
+			StmtKind::Struct { .. }
+			| StmtKind::Interface { .. }
+			| StmtKind::Enum { .. }
+			| StmtKind::Break
+			| StmtKind::Continue => {}
 			StmtKind::TryCatch {
 				try_statements,
 				catch_block,

diff --git a/libs/wingc/src/jsify.rs b/libs/wingc/src/jsify.rs
@@ -642,6 +642,10 @@ impl<'a> JSifier<'a> {
 				}
 			}
 			StmtKind::Class(class) => self.jsify_class(env, class, context),
+			StmtKind::Interface { .. } => {
+				// This is a no-op in JS
+				format!("")
+			}
 			StmtKind::Struct { .. } => {
 				// This is a no-op in JS
 				format!("")

diff --git a/libs/wingc/src/lib.rs b/libs/wingc/src/lib.rs
@@ -165,7 +165,7 @@ pub fn parse(source_path: &Path) -> (Scope, Diagnostics) {
 }
 
 pub fn type_check(scope: &mut Scope, types: &mut Types, source_path: &Path) -> Diagnostics {
-	let env = SymbolEnv::new(None, types.void(), false, false, Phase::Preflight, 0);
+	let env = SymbolEnv::new(None, types.void(), false, Phase::Preflight, 0);
 	scope.set_env(env);
 
 	// note: Globals are emitted here and wrapped in "{ ... }" blocks. Wrapping makes these emissions, actual