From 99ea99b386a032187411a465e959e0904a7e336b Mon Sep 17 00:00:00 2001
From: Gabriela Araujo Britto <gabrielaa@microsoft.com>
Date: Mon, 4 Apr 2022 19:53:41 -0300
Subject: [PATCH] Properly check singleton labeled tuple before unwrapping
 (#48554)

* properly check if singleton labeled tuple has optional element

* also check if labeled element is rest
---
 src/compiler/checker.ts                       |  6 ++-
 .../reference/singletonLabeledTuple.js        | 19 ++++++++
 .../reference/singletonLabeledTuple.symbols   | 33 ++++++++++++++
 .../reference/singletonLabeledTuple.types     | 45 +++++++++++++++++++
 tests/cases/compiler/singletonLabeledTuple.ts | 16 +++++++
 5 files changed, 118 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/singletonLabeledTuple.js
 create mode 100644 tests/baselines/reference/singletonLabeledTuple.symbols
 create mode 100644 tests/baselines/reference/singletonLabeledTuple.types
 create mode 100644 tests/cases/compiler/singletonLabeledTuple.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index b891a0ec6c0..7e144dd26f3 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15860,7 +15860,11 @@ namespace ts {
         }
 
         function isSingletonTupleType(node: TypeNode) {
-            return isTupleTypeNode(node) && length(node.elements) === 1 && !isOptionalTypeNode(node.elements[0]) && !isRestTypeNode(node.elements[0]);
+            return isTupleTypeNode(node) &&
+                length(node.elements) === 1 &&
+                !isOptionalTypeNode(node.elements[0]) &&
+                !isRestTypeNode(node.elements[0]) &&
+                !(isNamedTupleMember(node.elements[0]) && (node.elements[0].questionToken || node.elements[0].dotDotDotToken));
         }
 
         /**
diff --git a/tests/baselines/reference/singletonLabeledTuple.js b/tests/baselines/reference/singletonLabeledTuple.js
new file mode 100644
index 00000000000..e8299438f1e
--- /dev/null
+++ b/tests/baselines/reference/singletonLabeledTuple.js
@@ -0,0 +1,19 @@
+//// [singletonLabeledTuple.ts]
+type AliasOptional = [p?: number]
+
+// literal type vs type alias
+type Literal = [p?: number] extends [unknown] ? true : false // Expect `Literal` to be `false`
+type Alias = AliasOptional extends [unknown] ? true : false     // Expect `Alias` to be `false`
+
+// labeled tuple vs normal tuple
+type Labeled = [p?: number] extends [unknown] ? true : false   // Expect `Labeled` to be `false`
+type Normal = [number?] extends [unknown] ? true : false       // Expect `Normal` to be `false`
+
+
+type AliasRest = [...p: number[]];
+
+type LiteralRest = [...p: number[]] extends [unknown] ? true : false; // Expect `LiteralRest` to be `false`
+type AliasedRest = AliasRest extends [unknown] ? true : false; // Expect `AliasedRest` to be `false`
+type NormalRest = [...number[]] extends [unknown] ? true : false; // Expect `NormalRest` to be `false`
+
+//// [singletonLabeledTuple.js]
diff --git a/tests/baselines/reference/singletonLabeledTuple.symbols b/tests/baselines/reference/singletonLabeledTuple.symbols
new file mode 100644
index 00000000000..327ab83ac16
--- /dev/null
+++ b/tests/baselines/reference/singletonLabeledTuple.symbols
@@ -0,0 +1,33 @@
+=== tests/cases/compiler/singletonLabeledTuple.ts ===
+type AliasOptional = [p?: number]
+>AliasOptional : Symbol(AliasOptional, Decl(singletonLabeledTuple.ts, 0, 0))
+
+// literal type vs type alias
+type Literal = [p?: number] extends [unknown] ? true : false // Expect `Literal` to be `false`
+>Literal : Symbol(Literal, Decl(singletonLabeledTuple.ts, 0, 33))
+
+type Alias = AliasOptional extends [unknown] ? true : false     // Expect `Alias` to be `false`
+>Alias : Symbol(Alias, Decl(singletonLabeledTuple.ts, 3, 60))
+>AliasOptional : Symbol(AliasOptional, Decl(singletonLabeledTuple.ts, 0, 0))
+
+// labeled tuple vs normal tuple
+type Labeled = [p?: number] extends [unknown] ? true : false   // Expect `Labeled` to be `false`
+>Labeled : Symbol(Labeled, Decl(singletonLabeledTuple.ts, 4, 59))
+
+type Normal = [number?] extends [unknown] ? true : false       // Expect `Normal` to be `false`
+>Normal : Symbol(Normal, Decl(singletonLabeledTuple.ts, 7, 60))
+
+
+type AliasRest = [...p: number[]];
+>AliasRest : Symbol(AliasRest, Decl(singletonLabeledTuple.ts, 8, 56))
+
+type LiteralRest = [...p: number[]] extends [unknown] ? true : false; // Expect `LiteralRest` to be `false`
+>LiteralRest : Symbol(LiteralRest, Decl(singletonLabeledTuple.ts, 11, 34))
+
+type AliasedRest = AliasRest extends [unknown] ? true : false; // Expect `AliasedRest` to be `false`
+>AliasedRest : Symbol(AliasedRest, Decl(singletonLabeledTuple.ts, 13, 69))
+>AliasRest : Symbol(AliasRest, Decl(singletonLabeledTuple.ts, 8, 56))
+
+type NormalRest = [...number[]] extends [unknown] ? true : false; // Expect `NormalRest` to be `false`
+>NormalRest : Symbol(NormalRest, Decl(singletonLabeledTuple.ts, 14, 62))
+
diff --git a/tests/baselines/reference/singletonLabeledTuple.types b/tests/baselines/reference/singletonLabeledTuple.types
new file mode 100644
index 00000000000..44ca6b978d1
--- /dev/null
+++ b/tests/baselines/reference/singletonLabeledTuple.types
@@ -0,0 +1,45 @@
+=== tests/cases/compiler/singletonLabeledTuple.ts ===
+type AliasOptional = [p?: number]
+>AliasOptional : AliasOptional
+
+// literal type vs type alias
+type Literal = [p?: number] extends [unknown] ? true : false // Expect `Literal` to be `false`
+>Literal : false
+>true : true
+>false : false
+
+type Alias = AliasOptional extends [unknown] ? true : false     // Expect `Alias` to be `false`
+>Alias : false
+>true : true
+>false : false
+
+// labeled tuple vs normal tuple
+type Labeled = [p?: number] extends [unknown] ? true : false   // Expect `Labeled` to be `false`
+>Labeled : false
+>true : true
+>false : false
+
+type Normal = [number?] extends [unknown] ? true : false       // Expect `Normal` to be `false`
+>Normal : false
+>true : true
+>false : false
+
+
+type AliasRest = [...p: number[]];
+>AliasRest : AliasRest
+
+type LiteralRest = [...p: number[]] extends [unknown] ? true : false; // Expect `LiteralRest` to be `false`
+>LiteralRest : false
+>true : true
+>false : false
+
+type AliasedRest = AliasRest extends [unknown] ? true : false; // Expect `AliasedRest` to be `false`
+>AliasedRest : false
+>true : true
+>false : false
+
+type NormalRest = [...number[]] extends [unknown] ? true : false; // Expect `NormalRest` to be `false`
+>NormalRest : false
+>true : true
+>false : false
+
diff --git a/tests/cases/compiler/singletonLabeledTuple.ts b/tests/cases/compiler/singletonLabeledTuple.ts
new file mode 100644
index 00000000000..27d457ce35e
--- /dev/null
+++ b/tests/cases/compiler/singletonLabeledTuple.ts
@@ -0,0 +1,16 @@
+type AliasOptional = [p?: number]
+
+// literal type vs type alias
+type Literal = [p?: number] extends [unknown] ? true : false // Expect `Literal` to be `false`
+type Alias = AliasOptional extends [unknown] ? true : false     // Expect `Alias` to be `false`
+
+// labeled tuple vs normal tuple
+type Labeled = [p?: number] extends [unknown] ? true : false   // Expect `Labeled` to be `false`
+type Normal = [number?] extends [unknown] ? true : false       // Expect `Normal` to be `false`
+
+
+type AliasRest = [...p: number[]];
+
+type LiteralRest = [...p: number[]] extends [unknown] ? true : false; // Expect `LiteralRest` to be `false`
+type AliasedRest = AliasRest extends [unknown] ? true : false; // Expect `AliasedRest` to be `false`
+type NormalRest = [...number[]] extends [unknown] ? true : false; // Expect `NormalRest` to be `false`
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