From ca74f70061f65678905f98aeaf94a9373abab83f Mon Sep 17 00:00:00 2001
From: Sean Huh <sokwhan@google.com>
Date: Thu, 10 Sep 2026 23:23:06 +0000
Subject: [PATCH 1/2] Add conformance tests around type decaying

---
 .../simple/testdata/type_deduction.textproto  | 71 +++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/tests/simple/testdata/type_deduction.textproto b/tests/simple/testdata/type_deduction.textproto
index 1a0e2611..c69eb665 100644
--- a/tests/simple/testdata/type_deduction.textproto
+++ b/tests/simple/testdata/type_deduction.textproto
@@ -951,3 +951,74 @@ section {
     }
   }
 }
+
+section {
+  name: "type_decay"
+  description: "Tests for type decay / least-upper-bound generalization of types."
+  test {
+    name: "type_list_decay"
+    expr: "[int, bool, double]"
+    typed_result {
+      result {
+        list_value {
+          values {
+            type_value: "int"
+          }
+          values {
+            type_value: "bool"
+          }
+          values {
+            type_value: "double"
+          }
+        }
+      }
+      deduced_type {
+        list_type {
+          elem_type {
+            type {
+              dyn {}
+            }
+          }
+        }
+      }
+    }
+  }
+  test {
+    name: "type_ternary_decay"
+    expr: "true ? type(1) : type(1u)"
+    typed_result {
+      result {
+        type_value: "int"
+      }
+      deduced_type {
+        type {
+          dyn {}
+        }
+      }
+    }
+  }
+  test {
+    name: "type_free_param_list_decay"
+    description: "Type decay for list literal containing a free type parameter in TypeType and a concrete type."
+    expr: "[type([]), int]"
+    typed_result {
+      result {
+        list_value {
+          values {
+            type_value: "list"
+          }
+          values {
+            type_value: "int"
+          }
+        }
+      }
+      deduced_type {
+        list_type {
+          elem_type {
+            dyn {}
+          }
+        }
+      }
+    }
+  }
+}

From d4c6ed1bfce0016414a28bc9831e581126a2302d Mon Sep 17 00:00:00 2001
From: Sean Huh <sokwhan@google.com>
Date: Fri, 11 Sep 2026 00:03:17 +0000
Subject: [PATCH 2/2] Add more tests

---
 .../simple/testdata/type_deduction.textproto  | 80 ++++++++++++++++++-
 1 file changed, 78 insertions(+), 2 deletions(-)

diff --git a/tests/simple/testdata/type_deduction.textproto b/tests/simple/testdata/type_deduction.textproto
index c69eb665..f6cf94ca 100644
--- a/tests/simple/testdata/type_deduction.textproto
+++ b/tests/simple/testdata/type_deduction.textproto
@@ -954,7 +954,7 @@ section {
 
 section {
   name: "type_decay"
-  description: "Tests for type decay / least-upper-bound generalization of types."
+  description: "Tests for type decay / least-upper-bound generalization of type values."
   test {
     name: "type_list_decay"
     expr: "[int, bool, double]"
@@ -999,7 +999,7 @@ section {
   }
   test {
     name: "type_free_param_list_decay"
-    description: "Type decay for list literal containing a free type parameter in TypeType and a concrete type."
+    description: "Type decay for list literal containing a free type parameter in a type value and a concrete type."
     expr: "[type([]), int]"
     typed_result {
       result {
@@ -1021,4 +1021,80 @@ section {
       }
     }
   }
+  test {
+    name: "type_nested_list_decay"
+    description: "Type decay for nested list literal with differing type values."
+    expr: "[[type(1)], [type(1u)]]"
+    typed_result {
+      result {
+        list_value {
+          values {
+            list_value {
+              values {
+                type_value: "int"
+              }
+            }
+          }
+          values {
+            list_value {
+              values {
+                type_value: "uint"
+              }
+            }
+          }
+        }
+      }
+      deduced_type {
+        list_type {
+          elem_type {
+            list_type {
+              elem_type {
+                type {
+                  dyn {}
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+  test {
+    name: "type_free_param_list_concat"
+    description: "Type deduction for concatenated lists containing free type parameters in type values."
+    expr: "([] + [[type(1)]]) + [[type([])]]"
+    typed_result {
+      result {
+        list_value {
+          values {
+            list_value {
+              values {
+                type_value: "int"
+              }
+            }
+          }
+          values {
+            list_value {
+              values {
+                type_value: "list"
+              }
+            }
+          }
+        }
+      }
+      deduced_type {
+        list_type {
+          elem_type {
+            list_type {
+              elem_type {
+                type {
+                  dyn {}
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
 }