Only skip any checks for unwrapped tuples in conditionals, rather than all nondistributive conditionals for backcompat (#42447)

Author: weswigham

src/compiler/checker.ts

@@ -14647,6 +14647,7 @@ namespace ts {
             // types of the form 'A extends B ? X : C extends D ? Y : E extends F ? Z : ...' as a single construct for
             // purposes of resolution. This means such types aren't subject to the instatiation depth limiter.
             while (true) {
+                const isUnwrapped = isTypicalNondistributiveConditional(root);
                 const checkType = instantiateType(unwrapNondistributiveConditionalTuple(root, root.checkType), mapper);
                 const checkTypeInstantiable = isGenericObjectType(checkType) || isGenericIndexType(checkType);
                 const extendsType = instantiateType(unwrapNondistributiveConditionalTuple(root, root.extendsType), mapper);
@@ -14672,9 +14673,9 @@ namespace ts {
                     // types with type parameters mapped to the wildcard type, the most permissive instantiations
                     // possible (the wildcard type is assignable to and from all types). If those are not related,
                     // then no instantiations will be and we can just return the false branch type.
-                    if (!(inferredExtendsType.flags & TypeFlags.AnyOrUnknown) && ((checkType.flags & TypeFlags.Any && root.isDistributive) || !isTypeAssignableTo(getPermissiveInstantiation(checkType), getPermissiveInstantiation(inferredExtendsType)))) {
+                    if (!(inferredExtendsType.flags & TypeFlags.AnyOrUnknown) && ((checkType.flags & TypeFlags.Any && !isUnwrapped) || !isTypeAssignableTo(getPermissiveInstantiation(checkType), getPermissiveInstantiation(inferredExtendsType)))) {
                         // Return union of trueType and falseType for 'any' since it matches anything
-                        if (checkType.flags & TypeFlags.Any && root.isDistributive) {
+                        if (checkType.flags & TypeFlags.Any && !isUnwrapped) {
                             (extraTypes || (extraTypes = [])).push(instantiateType(getTypeFromTypeNode(root.node.trueType), combinedMapper || mapper));
                         }
                         // If falseType is an immediately nested conditional type that isn't distributive or has an

tests/baselines/reference/conditionalAnyCheckTypePicksBothBranches.errors.txt

@@ -0,0 +1,15 @@
+tests/cases/compiler/conditionalAnyCheckTypePicksBothBranches.ts(9,1): error TS2322: Type '0' is not assignable to type '1'.
+
+
+==== tests/cases/compiler/conditionalAnyCheckTypePicksBothBranches.ts (1 errors) ====
+    type T = any extends number ? 1 : 0;
+    let x: T;
+    x = 1;
+    x = 0; // not an error
+    
+    type U = [any] extends [number] ? 1 : 0;
+    let y: U;
+    y = 1;
+    y = 0; // error
+    ~
+!!! error TS2322: Type '0' is not assignable to type '1'.

tests/baselines/reference/conditionalAnyCheckTypePicksBothBranches.js

@@ -0,0 +1,18 @@
+//// [conditionalAnyCheckTypePicksBothBranches.ts]
+type T = any extends number ? 1 : 0;
+let x: T;
+x = 1;
+x = 0; // not an error
+
+type U = [any] extends [number] ? 1 : 0;
+let y: U;
+y = 1;
+y = 0; // error
+
+//// [conditionalAnyCheckTypePicksBothBranches.js]
+var x;
+x = 1;
+x = 0; // not an error
+var y;
+y = 1;
+y = 0; // error

tests/baselines/reference/conditionalAnyCheckTypePicksBothBranches.symbols

@@ -0,0 +1,27 @@
+=== tests/cases/compiler/conditionalAnyCheckTypePicksBothBranches.ts ===
+type T = any extends number ? 1 : 0;
+>T : Symbol(T, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 0, 0))
+
+let x: T;
+>x : Symbol(x, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 1, 3))
+>T : Symbol(T, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 0, 0))
+
+x = 1;
+>x : Symbol(x, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 1, 3))
+
+x = 0; // not an error
+>x : Symbol(x, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 1, 3))
+
+type U = [any] extends [number] ? 1 : 0;
+>U : Symbol(U, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 3, 6))
+
+let y: U;
+>y : Symbol(y, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 6, 3))
+>U : Symbol(U, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 3, 6))
+
+y = 1;
+>y : Symbol(y, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 6, 3))
+
+y = 0; // error
+>y : Symbol(y, Decl(conditionalAnyCheckTypePicksBothBranches.ts, 6, 3))
+

tests/baselines/reference/conditionalAnyCheckTypePicksBothBranches.types

@@ -0,0 +1,33 @@
+=== tests/cases/compiler/conditionalAnyCheckTypePicksBothBranches.ts ===
+type T = any extends number ? 1 : 0;
+>T : 0 | 1
+
+let x: T;
+>x : 0 | 1
+
+x = 1;
+>x = 1 : 1
+>x : 0 | 1
+>1 : 1
+
+x = 0; // not an error
+>x = 0 : 0
+>x : 0 | 1
+>0 : 0
+
+type U = [any] extends [number] ? 1 : 0;
+>U : 1
+
+let y: U;
+>y : 1
+
+y = 1;
+>y = 1 : 1
+>y : 1
+>1 : 1
+
+y = 0; // error
+>y = 0 : 0
+>y : 1
+>0 : 0
+

tests/baselines/reference/inferTypes1.types

@@ -257,7 +257,7 @@ type T61<T> = infer A extends infer B ? infer C : infer D;  // Error
 >T61 : T61<T>
 
 type T62<T> = U extends (infer U)[] ? U : U;  // Error
->T62 : unknown
+>T62 : any
 
 type T63<T> = T extends (infer A extends infer B ? infer C : infer D) ? string : number;
 >T63 : T63<T>

tests/baselines/reference/recursiveConditionalTypes.types

@@ -105,7 +105,7 @@ type TT3 = TupleOf<number, any>;
 >TT3 : number[]
 
 type TT4 = TupleOf<number, 100>;  // Depth error
->TT4 : [any, ...any[]]
+>TT4 : any
 
 function f22<N extends number, M extends N>(tn: TupleOf<number, N>, tm: TupleOf<number, M>) {
 >f22 : <N extends number, M extends N>(tn: TupleOf<number, N>, tm: TupleOf<number, M>) => void

tests/cases/compiler/conditionalAnyCheckTypePicksBothBranches.ts

@@ -0,0 +1,9 @@
+type T = any extends number ? 1 : 0;
+let x: T;
+x = 1;
+x = 0; // not an error
+
+type U = [any] extends [number] ? 1 : 0;
+let y: U;
+y = 1;
+y = 0; // error