optimisation

Summary: An micro-optimisation: if a type alias has no parameters, there is no reason to go with an empty substitution and the body can be just re-used Reviewed By: TD5 Differential Revision: D69180282 fbshipit-source-id: a47a7776bac0bddb96008a47dc7f361382c2156f
WhatsApp · Feb 5, 2025 · 6612edd · 6612edd
1 parent b26c920
commit 6612edd
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Showing 2 changed files with 14 additions and 6 deletions.
diff --git a/crates/eqwalizer/src/ast/contractivity.rs b/crates/eqwalizer/src/ast/contractivity.rs
@@ -330,9 +330,13 @@ impl StubContractivityChecker<'_> {
             .expanded_stub(self.project_id, ModuleName::new(id.module.as_str()))
             .map_err(|err| ContractivityCheckError::ErrorExpandingID(id.clone(), Box::new(err)))?;
         fn subst(decl: &TypeDecl, args: &[Type]) -> Type {
-            let sub: FxHashMap<u32, &Type> =
-                decl.params.iter().map(|v| v.n).zip(args.iter()).collect();
-            Subst { sub }.apply(decl.body.clone())
+            if decl.params.is_empty() {
+                decl.body.clone()
+            } else {
+                let sub: FxHashMap<u32, &Type> =
+                    decl.params.iter().map(|v| v.n).zip(args.iter()).collect();
+                Subst { sub }.apply(decl.body.clone())
+            }
         }
         Ok(stub
             .types

diff --git a/crates/eqwalizer/src/ast/variance_check.rs b/crates/eqwalizer/src/ast/variance_check.rs
@@ -383,9 +383,13 @@ impl VarianceChecker<'_> {
             .contractive_stub(self.project_id, ModuleName::new(id.module.as_str()))
             .map_err(|err| VarianceCheckError::ErrorExpandingID(id.clone(), Box::new(err)))?;
         fn subst(decl: &TypeDecl, args: &[Type]) -> Type {
-            let sub: FxHashMap<u32, &Type> =
-                decl.params.iter().map(|v| v.n).zip(args.iter()).collect();
-            Subst { sub }.apply(decl.body.clone())
+            if decl.params.is_empty() {
+                decl.body.clone()
+            } else {
+                let sub: FxHashMap<u32, &Type> =
+                    decl.params.iter().map(|v| v.n).zip(args.iter()).collect();
+                Subst { sub }.apply(decl.body.clone())
+            }
         }
         Ok(stub.types.get(&local_id).map(|t| subst(t, args)))
     }