From 529fc9e259ea03c2d72d0663f33cd613faffde6f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Wed, 30 Apr 2025 23:48:21 +0200
Subject: [PATCH] Don't obtain apparent type of contextual types being optional
 type variables

---
 src/compiler/checker.ts                       |  2 +-
 .../inferenceFromGenericClass1.symbols        | 81 +++++++++++++++++
 .../inferenceFromGenericClass1.types          | 91 +++++++++++++++++++
 .../compiler/inferenceFromGenericClass1.ts    | 32 +++++++
 4 files changed, 205 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/inferenceFromGenericClass1.symbols
 create mode 100644 tests/baselines/reference/inferenceFromGenericClass1.types
 create mode 100644 tests/cases/compiler/inferenceFromGenericClass1.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index be3965258a516..4a78b0405d657 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -32412,7 +32412,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             getContextualTypeForObjectLiteralMethod(node, contextFlags) :
             getContextualType(node, contextFlags);
         const instantiatedType = instantiateContextualType(contextualType, node, contextFlags);
-        if (instantiatedType && !(contextFlags && contextFlags & ContextFlags.NoConstraints && instantiatedType.flags & TypeFlags.TypeVariable)) {
+        if (instantiatedType && !(contextFlags && contextFlags & ContextFlags.NoConstraints && maybeTypeOfKind(getNonNullableType(instantiatedType), TypeFlags.TypeVariable))) {
             const apparentType = mapType(
                 instantiatedType,
                 // When obtaining apparent type of *contextual* type we don't want to get apparent type of mapped types.
diff --git a/tests/baselines/reference/inferenceFromGenericClass1.symbols b/tests/baselines/reference/inferenceFromGenericClass1.symbols
new file mode 100644
index 0000000000000..e9ddbf7516548
--- /dev/null
+++ b/tests/baselines/reference/inferenceFromGenericClass1.symbols
@@ -0,0 +1,81 @@
+//// [tests/cases/compiler/inferenceFromGenericClass1.ts] ////
+
+=== inferenceFromGenericClass1.ts ===
+// https://github.com/microsoft/TypeScript/issues/61633
+
+type AnyConstructor = new (...args: any[]) => object;
+>AnyConstructor : Symbol(AnyConstructor, Decl(inferenceFromGenericClass1.ts, 0, 0))
+>args : Symbol(args, Decl(inferenceFromGenericClass1.ts, 2, 27))
+
+class Container<T> {}
+>Container : Symbol(Container, Decl(inferenceFromGenericClass1.ts, 2, 53))
+>T : Symbol(T, Decl(inferenceFromGenericClass1.ts, 4, 16))
+
+declare function RenderFlagsMixin1<
+>RenderFlagsMixin1 : Symbol(RenderFlagsMixin1, Decl(inferenceFromGenericClass1.ts, 4, 21))
+
+  BaseClass extends AnyConstructor | undefined = undefined,
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 6, 35))
+>AnyConstructor : Symbol(AnyConstructor, Decl(inferenceFromGenericClass1.ts, 0, 0))
+
+>(Base?: BaseClass): BaseClass;
+>Base : Symbol(Base, Decl(inferenceFromGenericClass1.ts, 8, 2))
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 6, 35))
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 6, 35))
+
+const result1 = RenderFlagsMixin1(Container);
+>result1 : Symbol(result1, Decl(inferenceFromGenericClass1.ts, 10, 5))
+>RenderFlagsMixin1 : Symbol(RenderFlagsMixin1, Decl(inferenceFromGenericClass1.ts, 4, 21))
+>Container : Symbol(Container, Decl(inferenceFromGenericClass1.ts, 2, 53))
+
+declare function RenderFlagsMixin2<
+>RenderFlagsMixin2 : Symbol(RenderFlagsMixin2, Decl(inferenceFromGenericClass1.ts, 10, 45))
+
+  BaseClass extends AnyConstructor | undefined = undefined,
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 12, 35))
+>AnyConstructor : Symbol(AnyConstructor, Decl(inferenceFromGenericClass1.ts, 0, 0))
+
+>(Base: BaseClass): BaseClass;
+>Base : Symbol(Base, Decl(inferenceFromGenericClass1.ts, 14, 2))
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 12, 35))
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 12, 35))
+
+const result2 = RenderFlagsMixin2(Container);
+>result2 : Symbol(result2, Decl(inferenceFromGenericClass1.ts, 16, 5))
+>RenderFlagsMixin2 : Symbol(RenderFlagsMixin2, Decl(inferenceFromGenericClass1.ts, 10, 45))
+>Container : Symbol(Container, Decl(inferenceFromGenericClass1.ts, 2, 53))
+
+declare function RenderFlagsMixin3<
+>RenderFlagsMixin3 : Symbol(RenderFlagsMixin3, Decl(inferenceFromGenericClass1.ts, 16, 45))
+
+  BaseClass extends AnyConstructor | undefined = undefined,
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 18, 35))
+>AnyConstructor : Symbol(AnyConstructor, Decl(inferenceFromGenericClass1.ts, 0, 0))
+
+>(Base: BaseClass | number): BaseClass;
+>Base : Symbol(Base, Decl(inferenceFromGenericClass1.ts, 20, 2))
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 18, 35))
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 18, 35))
+
+const result3 = RenderFlagsMixin3(Container);
+>result3 : Symbol(result3, Decl(inferenceFromGenericClass1.ts, 22, 5))
+>RenderFlagsMixin3 : Symbol(RenderFlagsMixin3, Decl(inferenceFromGenericClass1.ts, 16, 45))
+>Container : Symbol(Container, Decl(inferenceFromGenericClass1.ts, 2, 53))
+
+declare function RenderFlagsMixin4<
+>RenderFlagsMixin4 : Symbol(RenderFlagsMixin4, Decl(inferenceFromGenericClass1.ts, 22, 45))
+
+  BaseClass extends AnyConstructor | undefined = undefined,
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 24, 35))
+>AnyConstructor : Symbol(AnyConstructor, Decl(inferenceFromGenericClass1.ts, 0, 0))
+
+>(Base?: BaseClass | number): BaseClass;
+>Base : Symbol(Base, Decl(inferenceFromGenericClass1.ts, 26, 2))
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 24, 35))
+>BaseClass : Symbol(BaseClass, Decl(inferenceFromGenericClass1.ts, 24, 35))
+
+const result4 = RenderFlagsMixin4(Container);
+>result4 : Symbol(result4, Decl(inferenceFromGenericClass1.ts, 28, 5))
+>RenderFlagsMixin4 : Symbol(RenderFlagsMixin4, Decl(inferenceFromGenericClass1.ts, 22, 45))
+>Container : Symbol(Container, Decl(inferenceFromGenericClass1.ts, 2, 53))
+
diff --git a/tests/baselines/reference/inferenceFromGenericClass1.types b/tests/baselines/reference/inferenceFromGenericClass1.types
new file mode 100644
index 0000000000000..3dc8570735248
--- /dev/null
+++ b/tests/baselines/reference/inferenceFromGenericClass1.types
@@ -0,0 +1,91 @@
+//// [tests/cases/compiler/inferenceFromGenericClass1.ts] ////
+
+=== inferenceFromGenericClass1.ts ===
+// https://github.com/microsoft/TypeScript/issues/61633
+
+type AnyConstructor = new (...args: any[]) => object;
+>AnyConstructor : AnyConstructor
+>               : ^^^^^^^^^^^^^^
+>args : any[]
+>     : ^^^^^
+
+class Container<T> {}
+>Container : Container<T>
+>          : ^^^^^^^^^^^^
+
+declare function RenderFlagsMixin1<
+>RenderFlagsMixin1 : <BaseClass extends AnyConstructor | undefined = undefined>(Base?: BaseClass) => BaseClass
+>                  : ^         ^^^^^^^^^                          ^^^^^^^^^^^^^^    ^^^         ^^^^^         
+
+  BaseClass extends AnyConstructor | undefined = undefined,
+>(Base?: BaseClass): BaseClass;
+>Base : BaseClass | undefined
+>     : ^^^^^^^^^^^^^^^^^^^^^
+
+const result1 = RenderFlagsMixin1(Container);
+>result1 : typeof Container
+>        : ^^^^^^^^^^^^^^^^
+>RenderFlagsMixin1(Container) : typeof Container
+>                             : ^^^^^^^^^^^^^^^^
+>RenderFlagsMixin1 : <BaseClass extends AnyConstructor | undefined = undefined>(Base?: BaseClass) => BaseClass
+>                  : ^         ^^^^^^^^^                          ^^^^^^^^^^^^^^    ^^^         ^^^^^         
+>Container : typeof Container
+>          : ^^^^^^^^^^^^^^^^
+
+declare function RenderFlagsMixin2<
+>RenderFlagsMixin2 : <BaseClass extends AnyConstructor | undefined = undefined>(Base: BaseClass) => BaseClass
+>                  : ^         ^^^^^^^^^                          ^^^^^^^^^^^^^^    ^^         ^^^^^         
+
+  BaseClass extends AnyConstructor | undefined = undefined,
+>(Base: BaseClass): BaseClass;
+>Base : BaseClass
+>     : ^^^^^^^^^
+
+const result2 = RenderFlagsMixin2(Container);
+>result2 : typeof Container
+>        : ^^^^^^^^^^^^^^^^
+>RenderFlagsMixin2(Container) : typeof Container
+>                             : ^^^^^^^^^^^^^^^^
+>RenderFlagsMixin2 : <BaseClass extends AnyConstructor | undefined = undefined>(Base: BaseClass) => BaseClass
+>                  : ^         ^^^^^^^^^                          ^^^^^^^^^^^^^^    ^^         ^^^^^         
+>Container : typeof Container
+>          : ^^^^^^^^^^^^^^^^
+
+declare function RenderFlagsMixin3<
+>RenderFlagsMixin3 : <BaseClass extends AnyConstructor | undefined = undefined>(Base: BaseClass | number) => BaseClass
+>                  : ^         ^^^^^^^^^                          ^^^^^^^^^^^^^^    ^^                  ^^^^^         
+
+  BaseClass extends AnyConstructor | undefined = undefined,
+>(Base: BaseClass | number): BaseClass;
+>Base : number | BaseClass
+>     : ^^^^^^^^^^^^^^^^^^
+
+const result3 = RenderFlagsMixin3(Container);
+>result3 : typeof Container
+>        : ^^^^^^^^^^^^^^^^
+>RenderFlagsMixin3(Container) : typeof Container
+>                             : ^^^^^^^^^^^^^^^^
+>RenderFlagsMixin3 : <BaseClass extends AnyConstructor | undefined = undefined>(Base: BaseClass | number) => BaseClass
+>                  : ^         ^^^^^^^^^                          ^^^^^^^^^^^^^^    ^^                  ^^^^^         
+>Container : typeof Container
+>          : ^^^^^^^^^^^^^^^^
+
+declare function RenderFlagsMixin4<
+>RenderFlagsMixin4 : <BaseClass extends AnyConstructor | undefined = undefined>(Base?: BaseClass | number) => BaseClass
+>                  : ^         ^^^^^^^^^                          ^^^^^^^^^^^^^^    ^^^                  ^^^^^         
+
+  BaseClass extends AnyConstructor | undefined = undefined,
+>(Base?: BaseClass | number): BaseClass;
+>Base : number | BaseClass | undefined
+>     : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+const result4 = RenderFlagsMixin4(Container);
+>result4 : typeof Container
+>        : ^^^^^^^^^^^^^^^^
+>RenderFlagsMixin4(Container) : typeof Container
+>                             : ^^^^^^^^^^^^^^^^
+>RenderFlagsMixin4 : <BaseClass extends AnyConstructor | undefined = undefined>(Base?: BaseClass | number) => BaseClass
+>                  : ^         ^^^^^^^^^                          ^^^^^^^^^^^^^^    ^^^                  ^^^^^         
+>Container : typeof Container
+>          : ^^^^^^^^^^^^^^^^
+
diff --git a/tests/cases/compiler/inferenceFromGenericClass1.ts b/tests/cases/compiler/inferenceFromGenericClass1.ts
new file mode 100644
index 0000000000000..0a4f087bbdac8
--- /dev/null
+++ b/tests/cases/compiler/inferenceFromGenericClass1.ts
@@ -0,0 +1,32 @@
+// @strict: true
+// @noEmit: true
+
+// https://github.com/microsoft/TypeScript/issues/61633
+
+type AnyConstructor = new (...args: any[]) => object;
+
+class Container<T> {}
+
+declare function RenderFlagsMixin1<
+  BaseClass extends AnyConstructor | undefined = undefined,
+>(Base?: BaseClass): BaseClass;
+
+const result1 = RenderFlagsMixin1(Container);
+
+declare function RenderFlagsMixin2<
+  BaseClass extends AnyConstructor | undefined = undefined,
+>(Base: BaseClass): BaseClass;
+
+const result2 = RenderFlagsMixin2(Container);
+
+declare function RenderFlagsMixin3<
+  BaseClass extends AnyConstructor | undefined = undefined,
+>(Base: BaseClass | number): BaseClass;
+
+const result3 = RenderFlagsMixin3(Container);
+
+declare function RenderFlagsMixin4<
+  BaseClass extends AnyConstructor | undefined = undefined,
+>(Base?: BaseClass | number): BaseClass;
+
+const result4 = RenderFlagsMixin4(Container);