Switch to a separate util

Author: Andarist

src/compiler/checker.ts

@@ -552,6 +552,7 @@ import {
     isImportOrExportSpecifier,
     isImportSpecifier,
     isImportTypeNode,
+    isInCompoundLikeAssignment,
     isIndexedAccessTypeNode,
     isInExpressionContext,
     isInfinityOrNaNString,
@@ -26662,8 +26663,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 if (!isReachableFlowNode(flow)) {
                     return unreachableNeverType;
                 }
-                const assignmentKind = getAssignmentTargetKind(node);
-                if (assignmentKind === AssignmentKind.Compound) {
+                if (getAssignmentTargetKind(node) === AssignmentKind.Compound) {
                     const flowType = getTypeAtFlowNode(flow.antecedent);
                     return createFlowType(getBaseTypeOfLiteralType(getTypeFromFlowType(flowType)), isIncomplete(flowType));
                 }
@@ -26674,7 +26674,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     const assignedType = getWidenedLiteralType(getInitialOrAssignedType(flow));
                     return isTypeAssignableTo(assignedType, declaredType) ? assignedType : anyArrayType;
                 }
-                const t = assignmentKind === AssignmentKind.CompoundLike ? getBaseTypeOfLiteralType(declaredType) : declaredType;
+                const t = isInCompoundLikeAssignment(node) ? getBaseTypeOfLiteralType(declaredType) : declaredType;
                 if (t.flags & TypeFlags.Union) {
                     return getAssignmentReducedType(t as UnionType, getInitialOrAssignedType(flow));
                 }
@@ -28037,10 +28037,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         // entities we simply return the declared type.
         if (localOrExportSymbol.flags & SymbolFlags.Variable) {
             if (assignmentKind === AssignmentKind.Definite) {
-                return type;
-            }
-            if (assignmentKind === AssignmentKind.CompoundLike) {
-                return getBaseTypeOfLiteralType(type);
+                return isInCompoundLikeAssignment(node) ? getBaseTypeOfLiteralType(type) : type;
             }
         }
         else if (isAlias) {
@@ -31576,7 +31573,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             }
             else {
                 const isSetonlyAccessor = prop.flags & SymbolFlags.SetAccessor && !(prop.flags & SymbolFlags.GetAccessor);
-                if (isSetonlyAccessor && assignmentKind !== AssignmentKind.Definite && assignmentKind !== AssignmentKind.CompoundLike) {
+                if (isSetonlyAccessor && assignmentKind !== AssignmentKind.Definite) {
                     error(node, Diagnostics.Private_accessor_was_defined_without_a_getter);
                 }
             }
@@ -31685,7 +31682,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         // assignment target, and the referenced property was declared as a variable, property,
         // accessor, or optional method.
         const assignmentKind = getAssignmentTargetKind(node);
-        if (assignmentKind === AssignmentKind.Definite || assignmentKind === AssignmentKind.CompoundLike) {
+        if (assignmentKind === AssignmentKind.Definite) {
             return removeMissingType(propType, !!(prop && prop.flags & SymbolFlags.Optional));
         }
         if (prop &&

src/compiler/utilities.ts

@@ -152,8 +152,6 @@ import {
     forEachChild,
     forEachChildRecursively,
     ForInOrOfStatement,
-    ForInStatement,
-    ForOfStatement,
     ForStatement,
     FunctionBody,
     FunctionDeclaration,
@@ -3417,9 +3415,9 @@ export function isInExpressionContext(node: Node): boolean {
                 forStatement.incrementor === node;
         case SyntaxKind.ForInStatement:
         case SyntaxKind.ForOfStatement:
-            const forInStatement = parent as ForInStatement | ForOfStatement;
-            return (forInStatement.initializer === node && forInStatement.initializer.kind !== SyntaxKind.VariableDeclarationList) ||
-                forInStatement.expression === node;
+            const forInOrOfStatement = parent as ForInOrOfStatement;
+            return (forInOrOfStatement.initializer === node && forInOrOfStatement.initializer.kind !== SyntaxKind.VariableDeclarationList) ||
+                forInOrOfStatement.expression === node;
         case SyntaxKind.TypeAssertionExpression:
         case SyntaxKind.AsExpression:
             return node === (parent as AssertionExpression).expression;
@@ -4464,27 +4462,31 @@ export function hasTypeArguments(node: Node): node is HasTypeArguments {
 
 /** @internal */
 export const enum AssignmentKind {
-    None, Definite, Compound, CompoundLike
+    None, Definite, Compound
 }
 
-/** @internal */
-export function getAssignmentTargetKind(node: Node): AssignmentKind {
-    let parent = node.parent;
-    while (true) {
+type AssignmentTarget =
+    | BinaryExpression
+    | PrefixUnaryExpression
+    | PostfixUnaryExpression
+    | ForInOrOfStatement;
+
+function getAssignmentTarget(node: Node): AssignmentTarget | undefined {
+    let parent: Node;
+    while (parent = node.parent) {
         switch (parent.kind) {
             case SyntaxKind.BinaryExpression:
-                const binaryOperator = (parent as BinaryExpression).operatorToken.kind;
-                return isAssignmentOperator(binaryOperator) && (parent as BinaryExpression).left === node ?
-                    binaryOperator === SyntaxKind.EqualsToken ? (isCompoundLikeAssignment(parent as BinaryExpression) ? AssignmentKind.CompoundLike : AssignmentKind.Definite) :
-                    isLogicalOrCoalescingAssignmentOperator(binaryOperator) ? AssignmentKind.Definite : AssignmentKind.Compound :
-                    AssignmentKind.None;
+                const binaryExpression = parent as BinaryExpression;
+                const binaryOperator = binaryExpression.operatorToken.kind;
+                return isAssignmentOperator(binaryOperator) && binaryExpression.left === node ? binaryExpression : undefined;
             case SyntaxKind.PrefixUnaryExpression:
             case SyntaxKind.PostfixUnaryExpression:
-                const unaryOperator = (parent as PrefixUnaryExpression | PostfixUnaryExpression).operator;
-                return unaryOperator === SyntaxKind.PlusPlusToken || unaryOperator === SyntaxKind.MinusMinusToken ? AssignmentKind.Compound : AssignmentKind.None;
+                const unaryExpression = (parent as PrefixUnaryExpression | PostfixUnaryExpression);
+                const unaryOperator = unaryExpression.operator;
+                return unaryOperator === SyntaxKind.PlusPlusToken || unaryOperator === SyntaxKind.MinusMinusToken ? unaryExpression : undefined;
             case SyntaxKind.ForInStatement:
             case SyntaxKind.ForOfStatement:
-                return (parent as ForInOrOfStatement).initializer === node ? AssignmentKind.Definite : AssignmentKind.None;
+                return parent as ForInOrOfStatement;
             case SyntaxKind.ParenthesizedExpression:
             case SyntaxKind.ArrayLiteralExpression:
             case SyntaxKind.SpreadElement:
@@ -4496,20 +4498,39 @@ export function getAssignmentTargetKind(node: Node): AssignmentKind {
                 break;
             case SyntaxKind.ShorthandPropertyAssignment:
                 if ((parent as ShorthandPropertyAssignment).name !== node) {
-                    return AssignmentKind.None;
+                    return undefined;
                 }
                 node = parent.parent;
                 break;
             case SyntaxKind.PropertyAssignment:
-                if ((parent as ShorthandPropertyAssignment).name === node) {
-                    return AssignmentKind.None;
+                if ((parent as PropertyAssignment).name === node) {
+                    return undefined;
                 }
                 node = parent.parent;
                 break;
-            default:
-                return AssignmentKind.None;
         }
-        parent = node.parent;
+    }
+    return undefined;
+}
+
+/** @internal */
+export function getAssignmentTargetKind(node: Node): AssignmentKind {
+    const target = getAssignmentTarget(node);
+    if (!target) {
+        return AssignmentKind.None;
+    }
+    switch (target.kind) {
+        case SyntaxKind.BinaryExpression:
+            const binaryOperator = target.operatorToken.kind;
+            return binaryOperator === SyntaxKind.EqualsToken || isLogicalOrCoalescingAssignmentOperator(binaryOperator) ?
+                AssignmentKind.Definite :
+                AssignmentKind.Compound;
+        case SyntaxKind.PrefixUnaryExpression:
+        case SyntaxKind.PostfixUnaryExpression:
+            return AssignmentKind.Compound;
+        case SyntaxKind.ForInStatement:
+        case SyntaxKind.ForOfStatement:
+            return AssignmentKind.Definite;
     }
 }
 
@@ -4519,14 +4540,20 @@ export function getAssignmentTargetKind(node: Node): AssignmentKind {
 // (Note that `p` is not a target in the above examples, only `a`.)
 /** @internal */
 export function isAssignmentTarget(node: Node): boolean {
-    return getAssignmentTargetKind(node) !== AssignmentKind.None;
+    return !!getAssignmentTarget(node);
 }
 
-function isCompoundLikeAssignment(assignment: BinaryExpression): boolean {
+function isCompoundLikeAssignment(assignment: AssignmentExpression<EqualsToken>): boolean {
     const right = skipParentheses(assignment.right);
     return right.kind === SyntaxKind.BinaryExpression && isAdditiveOperatorOrHigher((right as BinaryExpression).operatorToken.kind);
 }
 
+/** @internal */
+export function isInCompoundLikeAssignment(node: Node): boolean {
+    const target = getAssignmentTarget(node);
+    return !!target && isAssignmentExpression(target, /*excludeCompoundAssignment*/ true) && isCompoundLikeAssignment(target);
+}
+
 /** @internal */
 export type NodeWithPossibleHoistedDeclaration =
     | Block
@@ -4539,8 +4566,7 @@ export type NodeWithPossibleHoistedDeclaration =
     | DefaultClause
     | LabeledStatement
     | ForStatement
-    | ForInStatement
-    | ForOfStatement
+    | ForInOrOfStatement
     | DoStatement
     | WhileStatement
     | TryStatement