Remove redundant removeMissingType calls

Author: Andarist

src/compiler/checker.ts

@@ -6982,7 +6982,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             }
 
             function typeReferenceToTypeNode(type: TypeReference) {
-                let typeArguments: readonly Type[] = getTypeArguments(type);
+                const typeArguments = getTypeArguments(type);
                 if (type.target === globalArrayType || type.target === globalReadonlyArrayType) {
                     if (context.flags & NodeBuilderFlags.WriteArrayAsGenericType) {
                         const typeArgumentNode = typeToTypeNodeHelper(typeArguments[0], context);
@@ -6993,7 +6993,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     return type.target === globalArrayType ? arrayType : factory.createTypeOperatorNode(SyntaxKind.ReadonlyKeyword, arrayType);
                 }
                 else if (type.target.objectFlags & ObjectFlags.Tuple) {
-                    typeArguments = sameMap(typeArguments, (t, i) => removeMissingType(t, !!((type.target as TupleType).elementFlags[i] & ElementFlags.Optional)));
                     if (typeArguments.length > 0) {
                         const arity = getTypeReferenceArity(type);
                         const tupleConstituentNodes = mapToTypeNodes(typeArguments.slice(0, arity), context);
@@ -19928,11 +19927,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         let reportedError = false;
         for (const value of iterator) {
             const { errorNode: prop, innerExpression: next, nameType, errorMessage } = value;
-            let targetPropType = getBestMatchIndexedAccessTypeOrUndefined(source, target, nameType);
+            const targetPropType = getBestMatchIndexedAccessTypeOrUndefined(source, target, nameType);
             if (!targetPropType || targetPropType.flags & TypeFlags.IndexedAccess) continue; // Don't elaborate on indexes on generic variables
-            let sourcePropType = getIndexedAccessTypeOrUndefined(source, nameType);
+            const sourcePropType = getIndexedAccessTypeOrUndefined(source, nameType);
             if (!sourcePropType) continue;
-            const propName = getPropertyNameFromIndex(nameType, /*accessNode*/ undefined);
             if (!checkTypeRelatedTo(sourcePropType, targetPropType, relation, /*errorNode*/ undefined)) {
                 const elaborated = next && elaborateError(next, sourcePropType, targetPropType, relation, /*headMessage*/ undefined, containingMessageChain, errorOutputContainer);
                 reportedError = true;
@@ -19947,10 +19945,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                         resultObj.errors = [diag];
                     }
                     else {
-                        const targetIsOptional = !!(propName && (getPropertyOfType(target, propName) || unknownSymbol).flags & SymbolFlags.Optional);
-                        const sourceIsOptional = !!(propName && (getPropertyOfType(source, propName) || unknownSymbol).flags & SymbolFlags.Optional);
-                        targetPropType = removeMissingType(targetPropType, targetIsOptional);
-                        sourcePropType = removeMissingType(sourcePropType, targetIsOptional && sourceIsOptional);
                         const result = checkTypeRelatedTo(specificSource, targetPropType, relation, prop, errorMessage, containingMessageChain, resultObj);
                         if (result && specificSource !== sourcePropType) {
                             // If for whatever reason the expression type doesn't yield an error, make sure we still issue an error on the sourcePropType
@@ -29832,7 +29826,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 // If index is before any spread element and within the fixed part of the contextual tuple type, return
                 // the type of the contextual tuple element.
                 if ((firstSpreadIndex === undefined || index < firstSpreadIndex) && index < t.target.fixedLength) {
-                    return removeMissingType(getTypeArguments(t)[index], !!(t.target.elementFlags[index] && ElementFlags.Optional));
+                    return getTypeArguments(t)[index];
                 }
                 // When the length is known and the index is after all spread elements we compute the offset from the element
                 // to the end and the number of ending fixed elements in the contextual tuple type.
@@ -30534,7 +30528,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         const inConstContext = isConstContext(node);
         const contextualType = getApparentTypeOfContextualType(node, /*contextFlags*/ undefined);
         const inTupleContext = isSpreadIntoCallOrNew(node) || !!contextualType && someType(contextualType, isTupleLikeType);
-        let hasOmittedExpression = false;
         for (let i = 0; i < elementCount; i++) {
             const e = elements[i];
             if (e.kind === SyntaxKind.SpreadElement) {
@@ -30571,14 +30564,13 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 }
             }
             else if (exactOptionalPropertyTypes && e.kind === SyntaxKind.OmittedExpression) {
-                hasOmittedExpression = true;
-                elementTypes.push(undefinedOrMissingType);
-                elementFlags.push(ElementFlags.Optional);
+                elementTypes.push(undefinedType);
+                elementFlags.push(ElementFlags.Required);
             }
             else {
                 const type = checkExpressionForMutableLocation(e, checkMode, forceTuple);
-                elementTypes.push(addOptionality(type, /*isProperty*/ true, hasOmittedExpression));
-                elementFlags.push(hasOmittedExpression ? ElementFlags.Optional : ElementFlags.Required);
+                elementTypes.push(type);
+                elementFlags.push(ElementFlags.Required);
                 if (inTupleContext && checkMode && checkMode & CheckMode.Inferential && !(checkMode & CheckMode.SkipContextSensitive) && isContextSensitive(e)) {
                     const inferenceContext = getInferenceContext(node);
                     Debug.assert(inferenceContext); // In CheckMode.Inferential we should always have an inference context

tests/baselines/reference/strictOptionalProperties1.errors.txt

@@ -7,31 +7,28 @@ strictOptionalProperties1.ts(53,5): error TS2412: Type 'undefined' is not assign
 strictOptionalProperties1.ts(60,5): error TS2322: Type 'undefined' is not assignable to type 'string'.
 strictOptionalProperties1.ts(64,5): error TS2322: Type '[number, string?, string?]' is not assignable to type '[number, string?]'.
   Target allows only 2 element(s) but source may have more.
-strictOptionalProperties1.ts(71,5): error TS2322: Type '[number, never?]' is not assignable to type '[number, string?, boolean?]'.
+strictOptionalProperties1.ts(71,5): error TS2322: Type '[number, undefined]' is not assignable to type '[number, string?, boolean?]'.
   Type at position 1 in source is not compatible with type at position 1 in target.
     Type 'undefined' is not assignable to type 'string'.
-strictOptionalProperties1.ts(72,5): error TS2322: Type '[number, never?, never?]' is not assignable to type '[number, string?, boolean?]'.
+strictOptionalProperties1.ts(72,5): error TS2322: Type '[number, undefined, undefined]' is not assignable to type '[number, string?, boolean?]'.
   Type at position 1 in source is not compatible with type at position 1 in target.
     Type 'undefined' is not assignable to type 'string'.
-strictOptionalProperties1.ts(73,5): error TS2322: Type '[number, never?, never?, never?]' is not assignable to type '[number, string?, boolean?]'.
-  Target allows only 3 element(s) but source may have more.
-strictOptionalProperties1.ts(74,5): error TS2322: Type '[never?, never?, true?]' is not assignable to type '[number, string?, boolean?]'.
-  Source provides no match for required element at position 0 in target.
+strictOptionalProperties1.ts(73,5): error TS2322: Type '[number, undefined, undefined, undefined]' is not assignable to type '[number, string?, boolean?]'.
+  Source has 4 element(s) but target allows only 3.
+strictOptionalProperties1.ts(74,5): error TS2322: Type '[undefined, undefined, true]' is not assignable to type '[number, string?, boolean?]'.
+  Type at position 0 in source is not compatible with type at position 0 in target.
+    Type 'undefined' is not assignable to type 'number'.
 strictOptionalProperties1.ts(75,5): error TS2322: Type '[number, undefined, true]' is not assignable to type '[number, string?, boolean?]'.
   Type at position 1 in source is not compatible with type at position 1 in target.
     Type 'undefined' is not assignable to type 'string'.
 strictOptionalProperties1.ts(99,7): error TS2375: Type '{ foo: undefined; bar: string; }' is not assignable to type 'InputProps' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
   Types of property 'foo' are incompatible.
     Type 'undefined' is not assignable to type 'string'.
 strictOptionalProperties1.ts(105,7): error TS2322: Type '[number, undefined]' is not assignable to type '[number, string?, boolean?]'.
-  Type at position 1 in source is not compatible with type at position 1 in target.
-    Type 'undefined' is not assignable to type 'string'.
 strictOptionalProperties1.ts(106,7): error TS2322: Type '[number, string, undefined]' is not assignable to type '[number, string?, boolean?]'.
   Type at position 2 in source is not compatible with type at position 2 in target.
     Type 'undefined' is not assignable to type 'boolean'.
 strictOptionalProperties1.ts(107,7): error TS2322: Type '[number, undefined, undefined]' is not assignable to type '[number, string?, boolean?]'.
-  Type at position 1 in source is not compatible with type at position 1 in target.
-    Type 'undefined' is not assignable to type 'string'.
 strictOptionalProperties1.ts(111,7): error TS2375: Type '{ foo: undefined; }' is not assignable to type '{ foo?: number; }' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
   Types of property 'foo' are incompatible.
     Type 'undefined' is not assignable to type 'number'.
@@ -142,22 +139,23 @@ strictOptionalProperties1.ts(211,1): error TS2322: Type 'string | boolean | unde
         t = [42, 'abc', true];
         t = [42, ,];
         ~
-!!! error TS2322: Type '[number, never?]' is not assignable to type '[number, string?, boolean?]'.
+!!! error TS2322: Type '[number, undefined]' is not assignable to type '[number, string?, boolean?]'.
 !!! error TS2322:   Type at position 1 in source is not compatible with type at position 1 in target.
 !!! error TS2322:     Type 'undefined' is not assignable to type 'string'.
         t = [42, , ,];
         ~
-!!! error TS2322: Type '[number, never?, never?]' is not assignable to type '[number, string?, boolean?]'.
+!!! error TS2322: Type '[number, undefined, undefined]' is not assignable to type '[number, string?, boolean?]'.
 !!! error TS2322:   Type at position 1 in source is not compatible with type at position 1 in target.
 !!! error TS2322:     Type 'undefined' is not assignable to type 'string'.
         t = [42, , , ,];  // Error
         ~
-!!! error TS2322: Type '[number, never?, never?, never?]' is not assignable to type '[number, string?, boolean?]'.
-!!! error TS2322:   Target allows only 3 element(s) but source may have more.
+!!! error TS2322: Type '[number, undefined, undefined, undefined]' is not assignable to type '[number, string?, boolean?]'.
+!!! error TS2322:   Source has 4 element(s) but target allows only 3.
         t = [, , true];  // Error
         ~
-!!! error TS2322: Type '[never?, never?, true?]' is not assignable to type '[number, string?, boolean?]'.
-!!! error TS2322:   Source provides no match for required element at position 0 in target.
+!!! error TS2322: Type '[undefined, undefined, true]' is not assignable to type '[number, string?, boolean?]'.
+!!! error TS2322:   Type at position 0 in source is not compatible with type at position 0 in target.
+!!! error TS2322:     Type 'undefined' is not assignable to type 'number'.
         t = [42, undefined, true];  // Error
         ~
 !!! error TS2322: Type '[number, undefined, true]' is not assignable to type '[number, string?, boolean?]'.
@@ -199,8 +197,6 @@ strictOptionalProperties1.ts(211,1): error TS2322: Type 'string | boolean | unde
     const t2: [number, string?, boolean?] = [1, undefined];
           ~~
 !!! error TS2322: Type '[number, undefined]' is not assignable to type '[number, string?, boolean?]'.
-!!! error TS2322:   Type at position 1 in source is not compatible with type at position 1 in target.
-!!! error TS2322:     Type 'undefined' is not assignable to type 'string'.
     const t3: [number, string?, boolean?] = [1, "string", undefined];
           ~~
 !!! error TS2322: Type '[number, string, undefined]' is not assignable to type '[number, string?, boolean?]'.
@@ -209,8 +205,6 @@ strictOptionalProperties1.ts(211,1): error TS2322: Type 'string | boolean | unde
     const t4: [number, string?, boolean?] = [1, undefined, undefined];
           ~~
 !!! error TS2322: Type '[number, undefined, undefined]' is not assignable to type '[number, string?, boolean?]'.
-!!! error TS2322:   Type at position 1 in source is not compatible with type at position 1 in target.
-!!! error TS2322:     Type 'undefined' is not assignable to type 'string'.
 
     // Example from #13195
 

tests/baselines/reference/strictOptionalProperties1.types

@@ -328,33 +328,33 @@ function f5(t: [number, string?, boolean?]) {
 >true : true
 
     t = [42, ,];
->t = [42, ,] : [number, never?]
+>t = [42, ,] : [number, undefined]
 >t : [number, string?, boolean?]
->[42, ,] : [number, never?]
+>[42, ,] : [number, undefined]
 >42 : 42
 > : undefined
 
     t = [42, , ,];
->t = [42, , ,] : [number, never?, never?]
+>t = [42, , ,] : [number, undefined, undefined]
 >t : [number, string?, boolean?]
->[42, , ,] : [number, never?, never?]
+>[42, , ,] : [number, undefined, undefined]
 >42 : 42
 > : undefined
 > : undefined
 
     t = [42, , , ,];  // Error
->t = [42, , , ,] : [number, never?, never?, never?]
+>t = [42, , , ,] : [number, undefined, undefined, undefined]
 >t : [number, string?, boolean?]
->[42, , , ,] : [number, never?, never?, never?]
+>[42, , , ,] : [number, undefined, undefined, undefined]
 >42 : 42
 > : undefined
 > : undefined
 > : undefined
 
     t = [, , true];  // Error
->t = [, , true] : [never?, never?, true?]
+>t = [, , true] : [undefined, undefined, true]
 >t : [number, string?, boolean?]
->[, , true] : [never?, never?, true?]
+>[, , true] : [undefined, undefined, true]
 > : undefined
 > : undefined
 >true : true
@@ -379,34 +379,34 @@ function f6() {
 >2 : 2
 
     const t2 = [1, 2, ,] as const;
->t2 : readonly [1, 2, never?]
->[1, 2, ,] as const : readonly [1, 2, never?]
->[1, 2, ,] : readonly [1, 2, never?]
+>t2 : readonly [1, 2, undefined]
+>[1, 2, ,] as const : readonly [1, 2, undefined]
+>[1, 2, ,] : readonly [1, 2, undefined]
 >1 : 1
 >2 : 2
 > : undefined
 
     const t3 = [1, 2, , ,] as const;
->t3 : readonly [1, 2, never?, never?]
->[1, 2, , ,] as const : readonly [1, 2, never?, never?]
->[1, 2, , ,] : readonly [1, 2, never?, never?]
+>t3 : readonly [1, 2, undefined, undefined]
+>[1, 2, , ,] as const : readonly [1, 2, undefined, undefined]
+>[1, 2, , ,] : readonly [1, 2, undefined, undefined]
 >1 : 1
 >2 : 2
 > : undefined
 > : undefined
 
     const t4 = [1, , 2] as const;
->t4 : readonly [1, never?, 2?]
->[1, , 2] as const : readonly [1, never?, 2?]
->[1, , 2] : readonly [1, never?, 2?]
+>t4 : readonly [1, undefined, 2]
+>[1, , 2] as const : readonly [1, undefined, 2]
+>[1, , 2] : readonly [1, undefined, 2]
 >1 : 1
 > : undefined
 >2 : 2
 
     const t5 = [1, , , 2] as const;
->t5 : readonly [1, never?, never?, 2?]
->[1, , , 2] as const : readonly [1, never?, never?, 2?]
->[1, , , 2] : readonly [1, never?, never?, 2?]
+>t5 : readonly [1, undefined, undefined, 2]
+>[1, , , 2] as const : readonly [1, undefined, undefined, 2]
+>[1, , , 2] : readonly [1, undefined, undefined, 2]
 >1 : 1
 > : undefined
 > : undefined