fix: disregard type variable expectation for if expressions

Author: lowr

crates/hir-ty/src/infer/expr.rs

@@ -85,6 +85,7 @@ impl<'a> InferenceContext<'a> {
         let ty = match &self.body[tgt_expr] {
             Expr::Missing => self.err_ty(),
             &Expr::If { condition, then_branch, else_branch } => {
+                let expected = &expected.adjust_for_branches(&mut self.table);
                 self.infer_expr(
                     condition,
                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(Interner)),

crates/hir-ty/src/tests/coercion.rs

@@ -122,6 +122,23 @@ fn test() {
     )
 }
 
+#[test]
+fn if_else_adjust_for_branches_discard_type_var() {
+    check_no_mismatches(
+        r#"
+fn test() {
+    let f = || {
+        if true {
+            &""
+        } else {
+            ""
+        }
+    };
+}
+"#,
+    );
+}
+
 #[test]
 fn match_first_coerce() {
     check_no_mismatches(
@@ -182,6 +199,22 @@ fn test() {
     );
 }
 
+#[test]
+fn match_adjust_for_branches_discard_type_var() {
+    check_no_mismatches(
+        r#"
+fn test() {
+    let f = || {
+        match 0i32 {
+            0i32 => &"",
+            _ => "",
+        }
+    };
+}
+"#,
+    );
+}
+
 #[test]
 fn return_coerce_unknown() {
     check_types(