fix: don't always select trait impl when verifying trait constraints

compiler/noirc_frontend/src/elaborator/traits.rs

@@ -127,7 +127,7 @@ impl<'context> Elaborator<'context> {
                     let func_id = unresolved_trait.method_ids[&name.0.contents];
                     let mut where_clause = where_clause.to_vec();
 
-                    // Attach any trait constraints on the trait to the function
+                    // Attach any trait constraints on the trait to the function,
                     where_clause.extend(unresolved_trait.trait_def.where_clause.clone());
 
                     this.resolve_trait_function(

test_programs/compile_success_empty/regression_7038/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "regression_7038"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.30.0"
+
+[dependencies]

test_programs/compile_success_empty/regression_7038/src/main.nr

@@ -0,0 +1,40 @@
+trait BigNumTrait {}
+
+pub struct MyBigNum;
+
+impl crate::BigNumTrait for MyBigNum {}
+
+trait CurveParamsTrait<BigNum>
+where
+    BigNum: BigNumTrait,
+{
+    fn one();
+}
+
+pub struct BN254Params;
+impl CurveParamsTrait<MyBigNum> for BN254Params {
+
+    fn one() {}
+}
+
+trait BigCurveTrait {
+    fn two();
+}
+
+pub struct BigCurve<BigNum, CurveParams> {}
+
+type BN254 = BigCurve<MyBigNum, BN254Params>;
+
+impl<BigNum, CurveParams> BigCurveTrait for BigCurve<BigNum, CurveParams>
+where
+    BigNum: BigNumTrait,
+    CurveParams: CurveParamsTrait<BigNum>,
+{
+    fn two() {
+        let _ = CurveParams::one();
+    }
+}
+
+fn main() {
+    let _ = BN254::two();
+}

test_programs/compile_success_empty/regression_7038_2/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "regression_7038_2"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.30.0"
+
+[dependencies]

test_programs/compile_success_empty/regression_7038_2/src/main.nr

@@ -0,0 +1,37 @@
+trait BigNumTrait {}
+
+pub struct MyBigNum;
+
+impl crate::BigNumTrait for MyBigNum {}
+
+trait CurveParamsTrait<BigNum>
+where
+    BigNum: BigNumTrait,
+{
+    fn one() {}
+}
+
+pub struct BN254Params;
+impl CurveParamsTrait<MyBigNum> for BN254Params {}
+
+trait BigCurveTrait {
+    fn two();
+}
+
+pub struct BigCurve<BigNum, CurveParams> {}
+
+type BN254 = BigCurve<MyBigNum, BN254Params>;
+
+impl<BigNum, CurveParams> BigCurveTrait for BigCurve<BigNum, CurveParams>
+where
+    BigNum: BigNumTrait,
+    CurveParams: CurveParamsTrait<BigNum>,
+{
+    fn two() {
+        let _ = CurveParams::one();
+    }
+}
+
+fn main() {
+    let _ = BN254::two();
+}