Fixes issue of trait implementation not beeing used. (FuelLabs#3391)

The issue was caused by constraints used in generic functions having
trait name that does not contain any prefixes. This was causing
`get_methods_for_type_and_trait_name` to return no methods to be used.

This PR changes `get_methods_for_type_and_trait_name` so when a
`trait_name` without prefixes is provided it still tries to match using
the suffixes.

Closes FuelLabs#3326

Co-authored-by: Mohammad Fawaz <[email protected]>
Co-authored-by: Emily Herbert <[email protected]>

sway-core/src/type_system/type_parameter.rs

@@ -220,8 +220,34 @@ impl TypeParameter {
                     type_arguments: trait_type_arguments,
                 } = trait_constraint;
 
+                // Use trait name with module path as this is expected in get_methods_for_type_and_trait_name
+                let mut full_trait_name = trait_name.clone();
+                if trait_name.prefixes.is_empty() {
+                    if let Some(use_synonym) = ctx.namespace.use_synonyms.get(&trait_name.suffix) {
+                        let mut prefixes = use_synonym.0.clone();
+                        for mod_path in ctx.namespace.mod_path() {
+                            if prefixes[0].as_str() == mod_path.as_str() {
+                                prefixes.drain(0..1);
+                            } else {
+                                prefixes = use_synonym.0.clone();
+                                break;
+                            }
+                        }
+                        full_trait_name = CallPath {
+                            prefixes,
+                            suffix: trait_name.suffix.clone(),
+                            is_absolute: false,
+                        }
+                    }
+                }
+
                 let (trait_original_method_ids, trait_impld_method_ids) = check!(
-                    handle_trait(ctx.by_ref(), *type_id, trait_name, trait_type_arguments),
+                    handle_trait(
+                        ctx.by_ref(),
+                        *type_id,
+                        &full_trait_name,
+                        trait_type_arguments
+                    ),
                     continue,
                     warnings,
                     errors

test/src/e2e_vm_tests/test_programs/should_pass/stdlib/eq_custom_type/Forc.lock

@@ -0,0 +1,13 @@
+[[package]]
+name = 'core'
+source = 'path+from-root-33945E385D757681'
+
+[[package]]
+name = 'eq_custom_type'
+source = 'member'
+dependencies = ['std']
+
+[[package]]
+name = 'std'
+source = 'path+from-root-33945E385D757681'
+dependencies = ['core']

test/src/e2e_vm_tests/test_programs/should_pass/stdlib/eq_custom_type/Forc.toml

@@ -0,0 +1,8 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+entry = "main.sw"
+license = "Apache-2.0"
+name = "eq_custom_type"
+
+[dependencies]
+std = { path = "../../../../../../../sway-lib-std" }

test/src/e2e_vm_tests/test_programs/should_pass/stdlib/eq_custom_type/json_abi_oracle.json

@@ -0,0 +1,22 @@
+{
+  "functions": [
+    {
+      "inputs": [],
+      "name": "main",
+      "output": {
+        "name": "",
+        "type": 0,
+        "typeArguments": null
+      }
+    }
+  ],
+  "loggedTypes": [],
+  "types": [
+    {
+      "components": null,
+      "type": "bool",
+      "typeId": 0,
+      "typeParameters": null
+    }
+  ]
+}

test/src/e2e_vm_tests/test_programs/should_pass/stdlib/eq_custom_type/src/main.sw

@@ -0,0 +1,30 @@
+script;
+
+use core::ops::*;
+
+enum Error {
+    BoolError: bool,
+    U8Error: u8,
+}
+
+impl Eq for Error {
+    fn eq(self, other: Self) -> bool {
+        match (self, other) {
+            (Error::BoolError(val1), Error::BoolError(val2)) => val2 == val1,
+            (Error::U8Error(val1), Error::U8Error(val2)) => val2 == val1,
+            _ => false,
+        }
+    }
+}
+
+fn test_none_ok_or<T, E>(_val: T, default: E) where E: Eq {
+    match Option::None::<T>().ok_or(default) {
+        Result::Ok(_) => revert(0),
+        Result::Err(e) => assert(default == e),
+    }
+}
+
+fn main() -> bool {
+    test_none_ok_or(true, Error::BoolError(true));
+    return true;
+}

test/src/e2e_vm_tests/test_programs/should_pass/stdlib/eq_custom_type/test.toml

@@ -0,0 +1,3 @@
+category = "run"
+expected_result = { action = "return", value = 1 }
+validate_abi = true