From 749e37ba2edc5cdc9b49066e3a11b232636fd5c9 Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Wed, 22 Jun 2022 18:06:56 -0400
Subject: [PATCH] fix typo causing a panic in tuple unification

The `unifyObjectTypesToMap` function was inadvertently called from the
tuple-list unification function, which would panic since the value has
no attributes.

The given test example is possible speculatively unify, however we don't
have a codepath to recursively unify these yet, so we will just fail to
unify for now. This will fix the crashes in downstream consumers,
allowing the possibility of working around the shortcoming by using more
specific or different combinations of types.
---
 cty/convert/unify.go      |  5 ++---
 cty/convert/unify_test.go | 17 +++++++++++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/cty/convert/unify.go b/cty/convert/unify.go
index 144acd85..ac6b64db 100644
--- a/cty/convert/unify.go
+++ b/cty/convert/unify.go
@@ -447,7 +447,6 @@ func unifyTupleTypes(types []cty.Type, unsafe bool, hasDynamic bool) (cty.Type,
 			conversions[i] = GetConversion(ty, retTy)
 		}
 		if conversions[i] == nil {
-			// Shouldn't be reachable, since we were able to unify
 			return unifyTupleTypesToList(types, unsafe)
 		}
 	}
@@ -483,8 +482,8 @@ func unifyTupleTypesToList(types []cty.Type, unsafe bool) (cty.Type, []Conversio
 			conversions[i] = GetConversion(ty, retTy)
 		}
 		if conversions[i] == nil {
-			// Shouldn't be reachable, since we were able to unify
-			return unifyObjectTypesToMap(types, unsafe)
+			// no conversion was found
+			return cty.NilType, nil
 		}
 	}
 	return retTy, conversions
diff --git a/cty/convert/unify_test.go b/cty/convert/unify_test.go
index 8dd16c39..6ec5c671 100644
--- a/cty/convert/unify_test.go
+++ b/cty/convert/unify_test.go
@@ -163,6 +163,23 @@ func TestUnify(t *testing.T) {
 			cty.List(cty.Map(cty.String)),
 			[]bool{true, true},
 		},
+		{
+			// The second tuple value could be anything, so we can't unify
+			// these as a list.
+			// FIXME: While a unification is possible, we get a NilType for
+			// now until we can handle more complex recursive unification.
+			[]cty.Type{
+				cty.Tuple([]cty.Type{
+					cty.Object(map[string]cty.Type{
+						"a": cty.String,
+					}),
+					cty.DynamicPseudoType,
+				}),
+				cty.List(cty.DynamicPseudoType),
+			},
+			cty.NilType,
+			nil,
+		},
 		{
 			// unifies to the same result as above, since the only difference
 			// is the addition of a list