fix(compiler): confusing error when trying to use private constructor (…

…#6242)

Fixes #3331

Besides updating this error message, I also updated other error messages to standardize around the name "constructor". This is the name used most in the language reference, and it's probably the most familiar to users coming from TypeScript, so sticking to one terminology in our errors should help make the language feel more cohesive.

## Checklist

- [x] Title matches [Winglang's style guide](https://www.winglang.io/contributing/start-here/pull_requests#how-are-pull-request-titles-formatted)
- [x] Description explains motivation and solution
- [x] Tests added (always)
- [ ] Docs updated (only required for features)
- [ ] Added `pr/e2e-full` label if this feature requires end-to-end testing

*By submitting this pull request, I confirm that my contribution is made under the terms of the [Wing Cloud Contribution License](https://github.com/winglang/wing/blob/main/CONTRIBUTION_LICENSE.md)*.

docs/docs/03-language-reference.md

@@ -642,7 +642,7 @@ let handler2 = inflight() => {
 Bridge between preflight and inflight is crossed with the help of immutable data
 structures, "structs" (user definable and `Struct`), and the capture mechanism.
 
-Preflight class methods and initializers can receive an inflight function as an argument. This
+Preflight class methods and constructors can receive an inflight function as an argument. This
 enables preflight classes to define code that will be executed on a cloud compute platform such as
 lambda functions, docker, virtual machines etc.
 

examples/jsii-fixture/src/index.ts

@@ -31,6 +31,14 @@ export class JsiiClass {
   }
 }
 
+export class JsiiClassWithPrivateConstructor {
+  private constructor() {}
+
+  public static makeInstance(): JsiiClassWithPrivateConstructor {
+    return new JsiiClassWithPrivateConstructor();
+  }
+}
+
 /**
  * @callable
  */
@@ -47,4 +55,4 @@ export interface SomeStruct {
 
 export interface ISomeInterface {
   method(): void;
-}
+}

examples/tests/invalid/class.test.w

@@ -158,7 +158,7 @@ inflight class Jet extends Plane{
 //  ^^^^^^^^ Expected 1 positional argument(s) but got 0
   }
   constructor() {
-//^^^^^^^^^^^ To declare a initializer, use "init"
+//^^^^^^^^^^^ To declare a constructor, use "new"
   }
 }
 

examples/tests/invalid/inflight_class_dup_init.test.w

@@ -6,5 +6,5 @@ inflight class Foo {
   inflight new() {
 
   }
-//^ Multiple inflight initializers defined in class Foo
+//^ Multiple inflight constructors defined in class Foo
 }

examples/tests/invalid/private_constructor.test.w

@@ -0,0 +1,6 @@
+bring "jsii-fixture" as jsii_fixture;
+
+new jsii_fixture.JsiiClassWithPrivateConstructor();
+// error: constructor is private and only accessible within class "JsiiClassWithPrivateConstructor"
+
+jsii_fixture.JsiiClassWithPrivateConstructor.makeInstance(); // OK

libs/wingc/src/parser.rs

@@ -115,7 +115,6 @@ static RESERVED_WORDS: phf::Set<&'static str> = phf_set! {
 	"inflight",
 	"preflight",
 	"elif",
-	"init",
 	"any",
 	"num",
 	"str",
@@ -1228,14 +1227,14 @@ impl<'s> Parser<'s> {
 					if initializer.is_some() && !is_inflight {
 						self
 							.with_error::<Node>(
-								format!("Multiple initializers defined in class {}", name.name),
+								format!("Multiple constructors defined in class {}", name.name),
 								&class_element,
 							)
 							.err();
 					} else if inflight_initializer.is_some() && is_inflight {
 						self
 							.with_error::<Node>(
-								format!("Multiple inflight initializers defined in class {}", name.name),
+								format!("Multiple inflight constructors defined in class {}", name.name),
 								&class_element,
 							)
 							.err();
@@ -1244,7 +1243,7 @@ impl<'s> Parser<'s> {
 					let parameters = self.build_parameter_list(&parameters_node, class_phase, false)?;
 					if !parameters.is_empty() && is_inflight && class_phase == Phase::Preflight {
 						self
-							.with_error::<Node>("Inflight initializers cannot have parameters", &parameters_node)
+							.with_error::<Node>("Inflight constructors cannot have parameters", &parameters_node)
 							.err();
 					}
 
@@ -1303,7 +1302,7 @@ impl<'s> Parser<'s> {
 		for method in &methods {
 			if method.0.name == "constructor" {
 				Diagnostic::new(
-					"Reserved method name. Initializers are declared with \"init\"",
+					"Reserved method name. Constructors are declared with a method named \"new\"",
 					&method.0,
 				)
 				.report();

libs/wingc/src/type_check.rs

@@ -250,7 +250,7 @@ pub enum Type {
 	Enum(Enum),
 }
 
-pub const CLASS_INIT_NAME: &'static str = "init";
+pub const CLASS_INIT_NAME: &'static str = "new";
 pub const CLASS_INFLIGHT_INIT_NAME: &'static str = "$inflight_init";
 
 pub const CLOSURE_CLASS_HANDLE_METHOD: &'static str = "handle";
@@ -2314,17 +2314,28 @@ impl<'a> TypeChecker<'a> {
 					};
 
 					let lookup_res = class_env.lookup_ext(&init_method_name.into(), None);
-					let constructor_type = if let LookupResult::Found(k, _) = lookup_res {
-						k.as_variable().expect("Expected constructor to be a variable").type_
-					} else {
-						self.type_error(lookup_result_to_type_error(
-							lookup_res,
-							&Symbol {
-								name: CLASS_INIT_NAME.into(),
-								span: class_symbol.span.clone(),
-							},
-						));
-						return self.resolved_error();
+					let constructor_type = match lookup_res {
+						LookupResult::Found(k, _) => k.as_variable().expect("Expected constructor to be a variable").type_,
+						LookupResult::NotFound(_, _) => {
+							self.spanned_error(
+								exp,
+								format!("Constructor for class \"{}\" is private", class_symbol.name),
+							);
+							return self.resolved_error();
+						}
+						LookupResult::NotPublic(_, _)
+						| LookupResult::MultipleFound
+						| LookupResult::DefinedLater(_)
+						| LookupResult::ExpectedNamespace(_) => {
+							self.type_error(lookup_result_to_type_error(
+								lookup_res,
+								&Symbol {
+									name: CLASS_INIT_NAME.into(),
+									span: class_symbol.span.clone(),
+								},
+							));
+							return self.resolved_error();
+						}
 					};
 					let constructor_sig = constructor_type
 						.as_function_sig()
@@ -4798,7 +4809,7 @@ impl<'a> TypeChecker<'a> {
 			return;
 		};
 
-		// If the parent class is phase independent than its init name is just "init" regadless of
+		// If the parent class is phase independent than its constructor name is just "new" regardless of
 		// whether we're inflight or not.
 		let parent_init_name = if parent_class.as_class().unwrap().phase == Phase::Independent {
 			CLASS_INIT_NAME
@@ -4851,7 +4862,7 @@ impl<'a> TypeChecker<'a> {
 					self.spanned_error(
 						matching_field,
 						format!(
-							"\"{}\" cannot be initialized in the {} initializer",
+							"\"{}\" cannot be initialized in the {} constructor",
 							matching_field.name,
 							current_phase.to_lowercase()
 						),

libs/wingc/src/type_check/jsii_importer.rs

@@ -773,7 +773,7 @@ impl<'a> JsiiImporter<'a> {
 		let mut class_env = SymbolEnv::new(base_class_env, SymbolEnvKind::Type(new_type), class_phase, 0);
 		class_env.type_parameters = self.type_param_from_docs(&jsii_class_fqn, &jsii_class.docs);
 
-		// Add constructor to the class environment
+		// Add the class's constructor to the class environment, if the class has one which is public
 		let jsii_initializer = jsii_class.initializer.as_ref();
 		if let Some(initializer) = jsii_initializer {
 			let mut fn_params = vec![];

tools/hangar/__snapshots__/invalid.ts.snap

@@ -747,11 +747,11 @@ error: Call to super constructor can only be done from within a class constructo
     |    ^^^^^^^^ Call to super constructor can only be done from within a class constructor
 
 
-error: Reserved method name. Initializers are declared with \\"init\\"
+error: Reserved method name. Constructors are declared with a method named \\"new\\"
     --> ../../../examples/tests/invalid/class.test.w:160:3
     |
 160 |   constructor() {
-    |   ^^^^^^^^^^^ Reserved method name. Initializers are declared with \\"init\\"
+    |   ^^^^^^^^^^^ Reserved method name. Constructors are declared with a method named \\"new\\"
 
 
 error: Expected block
@@ -838,18 +838,18 @@ error: Inflight field \\"x\\" is not initialized
    |            ^ Inflight field \\"x\\" is not initialized
 
 
-error: \\"y\\" cannot be initialized in the inflight initializer
+error: \\"y\\" cannot be initialized in the inflight constructor
    --> ../../../examples/tests/invalid/class.test.w:61:10
    |
 61 |     this.y = 1;
-   |          ^ \\"y\\" cannot be initialized in the inflight initializer
+   |          ^ \\"y\\" cannot be initialized in the inflight constructor
 
 
-error: \\"x\\" cannot be initialized in the preflight initializer
+error: \\"x\\" cannot be initialized in the preflight constructor
    --> ../../../examples/tests/invalid/class.test.w:56:10
    |
 56 |     this.x = 1;
-   |          ^ \\"x\\" cannot be initialized in the preflight initializer
+   |          ^ \\"x\\" cannot be initialized in the preflight constructor
 
 
 error: Preflight field \\"y\\" is not initialized
@@ -2259,13 +2259,13 @@ Duration <DURATION>"
 `;
 
 exports[`inflight_class_dup_init.test.w 1`] = `
-"error: Multiple inflight initializers defined in class Foo
+"error: Multiple inflight constructors defined in class Foo
   --> ../../../examples/tests/invalid/inflight_class_dup_init.test.w:6:3
   |  
 6 | /   inflight new() {
 7 | | 
 8 | |   }
-  | \\\\---^ Multiple inflight initializers defined in class Foo
+  | \\\\---^ Multiple inflight constructors defined in class Foo
 
 
 
@@ -3249,6 +3249,21 @@ error: Expected type to be \\"str\\", but got \\"num\\" instead
 
 
 
+Tests 1 failed (1)
+Snapshots 1 skipped
+Test Files 1 failed (1)
+Duration <DURATION>"
+`;
+
+exports[`private_constructor.test.w 1`] = `
+"error: Constructor for class \\"JsiiClassWithPrivateConstructor\\" is private
+  --> ../../../examples/tests/invalid/private_constructor.test.w:3:1
+  |
+3 | new jsii_fixture.JsiiClassWithPrivateConstructor();
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Constructor for class \\"JsiiClassWithPrivateConstructor\\" is private
+
+
+
 Tests 1 failed (1)
 Snapshots 1 skipped
 Test Files 1 failed (1)
@@ -3529,32 +3544,32 @@ Duration <DURATION>"
 `;
 
 exports[`resource_init.test.w 1`] = `
-"error: Multiple initializers defined in class R
+"error: Multiple constructors defined in class R
   --> ../../../examples/tests/invalid/resource_init.test.w:3:3
   |
 3 |   new() {}
-  |   ^^^^^^^^ Multiple initializers defined in class R
+  |   ^^^^^^^^ Multiple constructors defined in class R
 
 
-error: Multiple inflight initializers defined in class R
+error: Multiple inflight constructors defined in class R
   --> ../../../examples/tests/invalid/resource_init.test.w:6:3
   |
 6 |   inflight new() {}
-  |   ^^^^^^^^^^^^^^^^^ Multiple inflight initializers defined in class R
+  |   ^^^^^^^^^^^^^^^^^ Multiple inflight constructors defined in class R
 
 
-error: Multiple inflight initializers defined in class R
+error: Multiple inflight constructors defined in class R
   --> ../../../examples/tests/invalid/resource_init.test.w:9:3
   |
 9 |   inflight new(x: num) {}
-  |   ^^^^^^^^^^^^^^^^^^^^^^^ Multiple inflight initializers defined in class R
+  |   ^^^^^^^^^^^^^^^^^^^^^^^ Multiple inflight constructors defined in class R
 
 
-error: Inflight initializers cannot have parameters
+error: Inflight constructors cannot have parameters
   --> ../../../examples/tests/invalid/resource_init.test.w:9:15
   |
 9 |   inflight new(x: num) {}
-  |               ^^^^^^^^ Inflight initializers cannot have parameters
+  |               ^^^^^^^^ Inflight constructors cannot have parameters