feat(compiler): log(struct) (#7018)

fixes: #6950
we can now log structs that all of their fields are stringable

## Checklist

- [ ] Title matches [Winglang's style guide](https://www.winglang.io/contributing/start-here/pull_requests#how-are-pull-request-titles-formatted)
- [ ] Description explains motivation and solution
- [ ] 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)*.

examples/tests/invalid/stringify.test.w

@@ -1,11 +1,21 @@
 class B {}
 let b = new B();
+struct Foo {
+ bar: B;
+ baz: str;
+}
+
+let foo: Foo = {bar: b, baz: "hello"};
+
 log("hello {b}");
-// ^ Error: expected type to be stringable 
+// ^ Expected type to be "stringable", but got "B" instead 
 
 let x: str? = nil;
 log("{x}");
-// ^ Error: expected type to be stringable
+// ^ Expected type to be "stringable", but got "str?" instead
 
 log(b);
-// ^ Error: expected type to be stringable
+// ^ Expected type to be "stringable", but got "B" instead
+
+log(foo);
+// ^ Expected type to be "stringable", but got "Foo" instead

examples/tests/valid/stringify.test.w

@@ -1,8 +1,14 @@
 enum MyEnum { A, B, C }
 
+struct Foo {
+  bar: str;
+}
+let foo = Foo { bar: "hello" };
+
 // If a value's type is stringable, it can be passed directly to the "log" function
 log("my string");
 log(42);
 log(true);
 log(Json { "cool": "beans" });
 log(MyEnum.A);
+log(foo);

libs/wingc/src/type_check.rs

@@ -775,6 +775,7 @@ impl Subtype for Type {
 			(Self::Json(_), Self::Json(_)) => true,
 			(Self::MutJson, Self::Stringable) => true,
 			(Self::Enum(_), Self::Stringable) => true,
+			(Self::Struct(s), Self::Stringable) => s.fields(true).map(|(_, v)| v.type_).all(|t| t.is_stringable()),
 			_ => false,
 		}
 	}
@@ -1127,6 +1128,14 @@ impl TypeRef {
 		matches!(**self, Type::Struct(_))
 	}
 
+	pub fn is_stringable_struct(&self) -> bool {
+		if let Type::Struct(ref s) = **self {
+			s.fields(true).map(|(_, v)| v.type_).all(|t| t.is_stringable())
+		} else {
+			false
+		}
+	}
+
 	pub fn is_map(&self) -> bool {
 		matches!(**self, Type::Map(_) | Type::MutMap(_))
 	}
@@ -1169,7 +1178,7 @@ impl TypeRef {
 		matches!(
 			**self,
 			Type::String | Type::Number | Type::Boolean | Type::Json(_) | Type::MutJson | Type::Enum(_) | Type::Anything
-		)
+		) || self.is_stringable_struct()
 	}
 
 	/// If this is a function and its last argument is a struct, return that struct.

tools/hangar/__snapshots__/invalid.ts.snap

@@ -4595,31 +4595,40 @@ Duration <DURATION>"
 
 exports[`stringify.test.w 1`] = `
 "error: Expected type to be "stringable", but got "B" instead
-  --> ../../../examples/tests/invalid/stringify.test.w:3:13
-  |
-3 | log("hello {b}");
-  |             ^
-  |
-  = hint: str, num, bool, json, and enums are stringable
+   --> ../../../examples/tests/invalid/stringify.test.w:10:13
+   |
+10 | log("hello {b}");
+   |             ^
+   |
+   = hint: str, num, bool, json, and enums are stringable
 
 
 error: Expected type to be "stringable", but got "str?" instead
-  --> ../../../examples/tests/invalid/stringify.test.w:7:7
-  |
-7 | log("{x}");
-  |       ^
-  |
-  = hint: str? is an optional, try unwrapping it with 'x ?? "nil"' or 'x!'
+   --> ../../../examples/tests/invalid/stringify.test.w:14:7
+   |
+14 | log("{x}");
+   |       ^
+   |
+   = hint: str? is an optional, try unwrapping it with 'x ?? "nil"' or 'x!'
 
 
 error: Expected type to be "stringable", but got "B" instead
-   --> ../../../examples/tests/invalid/stringify.test.w:10:5
+   --> ../../../examples/tests/invalid/stringify.test.w:17:5
    |
-10 | log(b);
+17 | log(b);
    |     ^
    |
    = hint: str, num, bool, json, and enums are stringable
 
+
+error: Expected type to be "stringable", but got "Foo" instead
+   --> ../../../examples/tests/invalid/stringify.test.w:20:5
+   |
+20 | log(foo);
+   |     ^^^
+   |
+   = hint: str, num, bool, json, and enums are stringable
+
 Tests 1 failed (1)
 Snapshots 1 skipped
 Test Files 1 failed (1)

tools/hangar/__snapshots__/test_corpus/valid/stringify.test.w_compile_tf-aws.md

@@ -44,11 +44,13 @@ class $Root extends $stdlib.std.Resource {
         return tmp;
       })({})
     ;
+    const foo = ({"bar": "hello"});
     console.log("my string");
     console.log(42);
     console.log(true);
     console.log(({"cool": "beans"}));
     console.log(MyEnum.A);
+    console.log(foo);
   }
 }
 const $APP = $PlatformManager.createApp({ outdir: $outdir, name: "stringify.test", rootConstruct: $Root, isTestEnvironment: $wing_is_test, entrypointDir: process.env['WING_SOURCE_DIR'], rootId: process.env['WING_ROOT_ID'] });

tools/hangar/__snapshots__/test_corpus/valid/stringify.test.w_test_sim.md

@@ -7,6 +7,7 @@ my string
 true
 { cool: 'beans' }
 A
+{ bar: 'hello' }
 pass ─ stringify.test.wsim (no tests)
 
 Tests 1 passed (1)