fix the other crash

Author: Andarist

src/compiler/checker.ts

@@ -27419,7 +27419,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                                         const impliedArity = constraint.target.fixedLength;
                                         if (startLength + impliedArity <= source.target.fixedLength) {
                                             inferFromTypes(sliceTupleType(source, startLength, sourceArity - (startLength + impliedArity)), elementTypes[startLength]);
-                                            inferFromTypes(getElementTypeOfSliceOfTupleType(source, startLength + impliedArity, endLength)!, elementTypes[startLength + 1]);
+                                            const restType = getElementTypeOfSliceOfTupleType(source, startLength + impliedArity, endLength);
+                                            if (restType) {
+                                                inferFromTypes(restType, elementTypes[startLength + 1]);
+                                            }
                                         }
                                     }
                                 }
@@ -27435,7 +27438,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                                             const startIndex = endIndex - impliedArity;
                                             const trailingSlice = createTupleType(getTypeArguments(source).slice(startIndex, endIndex), source.target.elementFlags.slice(startIndex, endIndex), /*readonly*/ false, source.target.labeledElementDeclarations && source.target.labeledElementDeclarations.slice(startIndex, endIndex));
 
-                                            inferFromTypes(getElementTypeOfSliceOfTupleType(source, startLength, endLength + impliedArity)!, elementTypes[startLength]);
+                                            const restType = getElementTypeOfSliceOfTupleType(source, startLength, endLength + impliedArity);
+                                            if (restType) {
+                                                inferFromTypes(restType, elementTypes[startLength]);
+                                            }
                                             inferFromTypes(trailingSlice, elementTypes[startLength + 1]);
                                         }
                                     }

tests/baselines/reference/inferTypesWithFixedTupleExtendsAtVariadicPosition.symbols

@@ -372,3 +372,28 @@ type SubTup2TrailingVariadicWithTrailingFixedElements3Test5 = SubTup2TrailingVar
 >SubTup2TrailingVariadicWithTrailingFixedElements3Test5 : Symbol(SubTup2TrailingVariadicWithTrailingFixedElements3Test5, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 141, 131))
 >SubTup2TrailingVariadicWithTrailingFixedElements3 : Symbol(SubTup2TrailingVariadicWithTrailingFixedElements3, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 128, 125))
 
+// variadic consuming all source elements, nothing left for rest
+type SubTup2VariadicTest5 = SubTup2Variadic<[a: 0, b: 1]>;
+>SubTup2VariadicTest5 : Symbol(SubTup2VariadicTest5, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 142, 125))
+>SubTup2Variadic : Symbol(SubTup2Variadic, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 10, 58))
+
+type SubTup2VariadicAndRestTest4 = SubTup2VariadicAndRest<[a: 0, b: 1]>;
+>SubTup2VariadicAndRestTest4 : Symbol(SubTup2VariadicAndRestTest4, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 145, 58))
+>SubTup2VariadicAndRest : Symbol(SubTup2VariadicAndRest, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 22, 57))
+
+type SubTup2TrailingVariadicTest5 = SubTup2TrailingVariadic<[b: 1, c: 2]>;
+>SubTup2TrailingVariadicTest5 : Symbol(SubTup2TrailingVariadicTest5, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 146, 72))
+>SubTup2TrailingVariadic : Symbol(SubTup2TrailingVariadic, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 33, 71))
+
+type SubTup2RestAndTrailingVariadic2Test4 = SubTup2RestAndTrailingVariadic2<[b: 1, c: 2]>;
+>SubTup2RestAndTrailingVariadic2Test4 : Symbol(SubTup2RestAndTrailingVariadic2Test4, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 147, 74))
+>SubTup2RestAndTrailingVariadic2 : Symbol(SubTup2RestAndTrailingVariadic2, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 45, 73))
+
+type SubTup2VariadicWithLeadingFixedElements3Test6 = SubTup2VariadicWithLeadingFixedElements3<[a: 0, b: 1, c: 2]>;
+>SubTup2VariadicWithLeadingFixedElements3Test6 : Symbol(SubTup2VariadicWithLeadingFixedElements3Test6, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 148, 90))
+>SubTup2VariadicWithLeadingFixedElements3 : Symbol(SubTup2VariadicWithLeadingFixedElements3, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 85, 107))
+
+type SubTup2TrailingVariadicWithTrailingFixedElements3Test6 = SubTup2TrailingVariadicWithTrailingFixedElements3<[b: 1, c: 2, d: 3]>;
+>SubTup2TrailingVariadicWithTrailingFixedElements3Test6 : Symbol(SubTup2TrailingVariadicWithTrailingFixedElements3Test6, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 149, 114))
+>SubTup2TrailingVariadicWithTrailingFixedElements3 : Symbol(SubTup2TrailingVariadicWithTrailingFixedElements3, Decl(inferTypesWithFixedTupleExtendsAtVariadicPosition.ts, 128, 125))
+

tests/baselines/reference/inferTypesWithFixedTupleExtendsAtVariadicPosition.types

@@ -308,3 +308,28 @@ type SubTup2TrailingVariadicWithTrailingFixedElements3Test5 = SubTup2TrailingVar
 >SubTup2TrailingVariadicWithTrailingFixedElements3Test5 : never
 >                                                       : ^^^^^
 
+// variadic consuming all source elements, nothing left for rest
+type SubTup2VariadicTest5 = SubTup2Variadic<[a: 0, b: 1]>;
+>SubTup2VariadicTest5 : [a: 0, b: 1]
+>                     : ^^^^^^^^^^^^
+
+type SubTup2VariadicAndRestTest4 = SubTup2VariadicAndRest<[a: 0, b: 1]>;
+>SubTup2VariadicAndRestTest4 : [a: 0, b: 1, unknown]
+>                            : ^^^^^^^^^^^^^^^^^^^^^
+
+type SubTup2TrailingVariadicTest5 = SubTup2TrailingVariadic<[b: 1, c: 2]>;
+>SubTup2TrailingVariadicTest5 : [b: 1, c: 2]
+>                             : ^^^^^^^^^^^^
+
+type SubTup2RestAndTrailingVariadic2Test4 = SubTup2RestAndTrailingVariadic2<[b: 1, c: 2]>;
+>SubTup2RestAndTrailingVariadic2Test4 : [unknown, b: 1, c: 2]
+>                                     : ^^^^^^^^^^^^^^^^^^^^^
+
+type SubTup2VariadicWithLeadingFixedElements3Test6 = SubTup2VariadicWithLeadingFixedElements3<[a: 0, b: 1, c: 2]>;
+>SubTup2VariadicWithLeadingFixedElements3Test6 : [[b: 1, c: 2], unknown]
+>                                              : ^^^^^^^^^^^^^^^^^^^^^^^
+
+type SubTup2TrailingVariadicWithTrailingFixedElements3Test6 = SubTup2TrailingVariadicWithTrailingFixedElements3<[b: 1, c: 2, d: 3]>;
+>SubTup2TrailingVariadicWithTrailingFixedElements3Test6 : [unknown, [b: 1, c: 2]]
+>                                                       : ^^^^^^^^^^^^^^^^^^^^^^^
+

tests/cases/compiler/inferTypesWithFixedTupleExtendsAtVariadicPosition.ts

@@ -145,3 +145,11 @@ type SubTup2TrailingVariadicWithTrailingFixedElements3Test2 = SubTup2TrailingVar
 type SubTup2TrailingVariadicWithTrailingFixedElements3Test3 = SubTup2TrailingVariadicWithTrailingFixedElements3<[...a: 0[], b: 1, c: 2]>;
 type SubTup2TrailingVariadicWithTrailingFixedElements3Test4 = SubTup2TrailingVariadicWithTrailingFixedElements3<[...a: 0[], b: 1]>;
 type SubTup2TrailingVariadicWithTrailingFixedElements3Test5 = SubTup2TrailingVariadicWithTrailingFixedElements3<[...a: 0[]]>;
+
+// variadic consuming all source elements, nothing left for rest
+type SubTup2VariadicTest5 = SubTup2Variadic<[a: 0, b: 1]>;
+type SubTup2VariadicAndRestTest4 = SubTup2VariadicAndRest<[a: 0, b: 1]>;
+type SubTup2TrailingVariadicTest5 = SubTup2TrailingVariadic<[b: 1, c: 2]>;
+type SubTup2RestAndTrailingVariadic2Test4 = SubTup2RestAndTrailingVariadic2<[b: 1, c: 2]>;
+type SubTup2VariadicWithLeadingFixedElements3Test6 = SubTup2VariadicWithLeadingFixedElements3<[a: 0, b: 1, c: 2]>;
+type SubTup2TrailingVariadicWithTrailingFixedElements3Test6 = SubTup2TrailingVariadicWithTrailingFixedElements3<[b: 1, c: 2, d: 3]>;