Bug fix to type inference with placeholder types for nested types (Fu…

…elLabs#3764) This PR fixes a bug relating to type substitution for placeholder types. The fix was to update the code path for placeholder type substitution from "no substitution" to "substitute if a match is found". This PR also changes the internal data structure of the `TypeMapping` type from a `Vec<(TypeId, TypeId)>` to a `BTreeMap<TypeId, TypeId>` because during debugging I noticed that there were duplicates and this could lead to wasted compute. Closes FuelLabs#3741 Co-authored-by: emilyaherbert <[email protected]>
mehtavishwa30 · Jan 12, 2023 · a2ccf3c · a2ccf3c
1 parent 8f6b21d
commit a2ccf3c
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Showing 3 changed files with 55 additions and 9 deletions.
diff --git a/sway-core/src/type_system/type_mapping.rs b/sway-core/src/type_system/type_mapping.rs
@@ -1,4 +1,4 @@
-use std::fmt;
+use std::{collections::BTreeMap, fmt};
 
 use super::*;
 use crate::engine_threading::*;
@@ -9,7 +9,7 @@ type DestinationType = TypeId;
 /// The [TypeMapping] is used to create a mapping between a [SourceType] (LHS)
 /// and a [DestinationType] (RHS).
 pub(crate) struct TypeMapping {
-    mapping: Vec<(SourceType, DestinationType)>,
+    mapping: BTreeMap<SourceType, DestinationType>,
 }
 
 impl DisplayWithEngines for TypeMapping {
@@ -131,7 +131,7 @@ impl TypeMapping {
             type_engine.look_up_type_id(subset),
         ) {
             (TypeInfo::UnknownGeneric { .. }, _) => TypeMapping {
-                mapping: vec![(superset, subset)],
+                mapping: BTreeMap::from([(superset, subset)]),
             },
             (
                 TypeInfo::Custom {
@@ -241,10 +241,12 @@ impl TypeMapping {
             | (TypeInfo::ErrorRecovery, TypeInfo::ErrorRecovery)
             | (TypeInfo::Str(_), TypeInfo::Str(_))
             | (TypeInfo::UnsignedInteger(_), TypeInfo::UnsignedInteger(_))
-            | (TypeInfo::ContractCaller { .. }, TypeInfo::ContractCaller { .. }) => {
-                TypeMapping { mapping: vec![] }
-            }
-            _ => TypeMapping { mapping: vec![] },
+            | (TypeInfo::ContractCaller { .. }, TypeInfo::ContractCaller { .. }) => TypeMapping {
+                mapping: BTreeMap::new(),
+            },
+            _ => TypeMapping {
+                mapping: BTreeMap::new(),
+            },
         }
     }
 
@@ -281,7 +283,7 @@ impl TypeMapping {
         let mapping = type_parameters
             .into_iter()
             .zip(type_arguments.into_iter())
-            .collect::<Vec<_>>();
+            .collect();
         TypeMapping { mapping }
     }
 
@@ -309,7 +311,7 @@ impl TypeMapping {
         match type_info {
             TypeInfo::Custom { .. } => iter_for_match(engines, self, &type_info),
             TypeInfo::UnknownGeneric { .. } => iter_for_match(engines, self, &type_info),
-            TypeInfo::Placeholder(_) => None,
+            TypeInfo::Placeholder(_) => iter_for_match(engines, self, &type_info),
             TypeInfo::Struct {
                 fields,
                 name,

diff --git a/test/src/e2e_vm_tests/test_programs/should_pass/language/generic_type_inference/src/main.sw b/test/src/e2e_vm_tests/test_programs/should_pass/language/generic_type_inference/src/main.sw
@@ -1,5 +1,11 @@
 script;
 
+dep utils;
+
+use std::assert::assert;
+
+use utils::*;
+
 struct CustomType {
     name: str[3],
 }
@@ -9,8 +15,37 @@ enum MyResult<T, E> {
     Err: E,
 }
 
+struct SomeStruct<T> {
+    a: T,
+}
+
+fn simple_vec_test() {
+    let mut vec1 = Vec::new();
+    let mut vec2 = Vec::new();
+
+    vec2.push(54u32);
+    vec1.push(SomeStruct { a: 42 });
+
+    assert(vec1.get(0).unwrap().a == 42);
+    assert(vec2.get(0).unwrap() == 54u32);
+}
+
+fn complex_vec_test() {
+    let mut exp_vec_in_a_vec_in_a_struct_in_a_vec = Vec::new();
+    let mut inner_vec_1 = Vec::new();
+    let inner_inner_vec_1 = vec_from([0, 1, 2]);
+
+    inner_vec_1.push(inner_inner_vec_1);
+    exp_vec_in_a_vec_in_a_struct_in_a_vec.push(SomeStruct { a: inner_vec_1 });
+
+    assert(inner_vec_1.get(0).unwrap().get(1).unwrap() == 1);
+    assert(exp_vec_in_a_vec_in_a_struct_in_a_vec.get(0).unwrap().a.get(0).unwrap().get(2).unwrap() == 2);
+}
+
 fn main() {
     sell_product();
+    simple_vec_test();
+    complex_vec_test();
 }
 
 fn sell_product() -> MyResult<bool, CustomType> {

diff --git a/test/src/e2e_vm_tests/test_programs/should_pass/language/generic_type_inference/src/utils.sw b/test/src/e2e_vm_tests/test_programs/should_pass/language/generic_type_inference/src/utils.sw
@@ -0,0 +1,9 @@
+library utils;
+
+pub fn vec_from(vals: [u32; 3]) -> Vec<u32> {
+    let mut vec = Vec::new();
+    vec.push(vals[0]);
+    vec.push(vals[1]);
+    vec.push(vals[2]);
+    vec
+}