Made sure closure would have the same id on call and defintion.

Closes #6920

crates/cairo-lang-lowering/src/ids.rs

@@ -359,7 +359,16 @@ pub trait SemanticFunctionIdEx {
 }
 impl SemanticFunctionIdEx for semantic::FunctionId {
     fn lowered(&self, db: &dyn LoweringGroup) -> FunctionId {
-        FunctionLongId::Semantic(*self).intern(db)
+        let ret = FunctionLongId::Semantic(*self).intern(db);
+        // If the function is generated, we need to check if it has a body, so we can return its
+        // generated function id.
+        // TODO(orizi): This is a hack, we should have a better way to do this.
+        if let Ok(Some(body)) = ret.body(db) {
+            if let Ok(id) = body.function_id(db) {
+                return id;
+            }
+        }
+        ret
     }
 }
 impl<'a> DebugWithDb<dyn LoweringGroup + 'a> for FunctionLongId {

tests/bug_samples/cairo_project.toml

@@ -3,3 +3,7 @@ bug_samples = "."
 
 [config.global]
 edition = "2023_10"
+
+[config.global.experimental_features]
+negative_impls = true
+associated_item_constraints = true

tests/bug_samples/issue6920.cairo

@@ -0,0 +1,11 @@
+#[test]
+fn uninlined_closure_test() {
+    let uninlined_closure = 
+        || {
+            let a: felt252 = 256;
+            format!(
+                "wow such amazing calcs {a} wow such amazing calcs {a} wow such amazing calcs {a}",
+            );
+        };
+    let _ = uninlined_closure();
+}

tests/bug_samples/lib.cairo

@@ -51,6 +51,7 @@ mod issue5967;
 mod issue6580;
 mod issue6623;
 mod issue6755;
+mod issue6920;
 mod loop_break_in_match;
 mod loop_only_change;
 mod partial_param_local;