typescript-eslint · bradzacher · Feb 27, 2023
diff --git a/packages/typescript-estree/src/convert-comments.ts b/packages/typescript-estree/src/convert-comments.ts
@@ -26,7 +26,6 @@ export function convertComments(
           ? AST_TOKEN_TYPES.Line
           : AST_TOKEN_TYPES.Block;
       const range: TSESTree.Range = [comment.pos, comment.end];
-      const loc = getLocFor(range[0], range[1], ast);
 
       // both comments start with 2 characters - /* or //
       const textStart = range[0] + 2;
@@ -40,7 +39,7 @@ export function convertComments(
         type,
         value: code.slice(textStart, textStart + textEnd),
         range,
-        loc,
+        loc: getLocFor(range[0], range[1], ast),
       });
     },
     ast,

diff --git a/packages/typescript-estree/src/convert.ts b/packages/typescript-estree/src/convert.ts
@@ -3,7 +3,7 @@
 import * as ts from 'typescript';
 
 import { getDecorators, getModifiers } from './getModifiers';
-import type { TSError } from './node-utils';
+import type { OptionalRangeAndLoc, TSError } from './node-utils';
 import {
   canContainDirective,
   createError,
@@ -251,7 +251,7 @@ export class Converter {
 
   private createNode<T extends TSESTree.Node = TSESTree.Node>(
     node: TSESTreeToTSNode<T>,
-    data: TSESTree.OptionalRangeAndLoc<T>,
+    data: OptionalRangeAndLoc<T>,
   ): T {
     const result = data;
     if (!result.range) {
@@ -2820,7 +2820,7 @@ export class Converter {
                 id,
                 body,
                 global: true,
-              } satisfies TSESTree.OptionalRangeAndLoc<
+              } satisfies OptionalRangeAndLoc<
                 Omit<TSESTree.TSModuleDeclarationGlobal, 'type'>
               >;
             } else if (node.flags & ts.NodeFlags.Namespace) {
@@ -2834,15 +2834,15 @@ export class Converter {
                 kind: 'namespace',
                 id,
                 body,
-              } satisfies TSESTree.OptionalRangeAndLoc<
+              } satisfies OptionalRangeAndLoc<
                 Omit<TSESTree.TSModuleDeclarationNamespace, 'type'>
               >;
             } else {
               return {
                 kind: 'module',
                 id,
                 ...(body != null ? { body } : {}),
-              } satisfies TSESTree.OptionalRangeAndLoc<
+              } satisfies OptionalRangeAndLoc<
                 Omit<TSESTree.TSModuleDeclarationModule, 'type'>
               >;
             }

diff --git a/packages/typescript-estree/src/node-utils.ts b/packages/typescript-estree/src/node-utils.ts
@@ -181,9 +181,27 @@ export function getLocFor(
   end: number,
   ast: ts.SourceFile,
 ): TSESTree.SourceLocation {
+  let locStart: TSESTree.Position | null = null;
+  let locEnd: TSESTree.Position | null = null;
   return {
-    start: getLineAndCharacterFor(start, ast),
-    end: getLineAndCharacterFor(end, ast),
+    get start(): TSESTree.Position {
+      if (locStart == null) {
+        locStart = getLineAndCharacterFor(start, ast);
+      }
+      return locStart;
+    },
+    set start(val: TSESTree.Position) {
+      locStart = val;
+    },
+    get end(): TSESTree.Position {
+      if (locEnd == null) {
+        locEnd = getLineAndCharacterFor(end, ast);
+      }
+      return locEnd;
+    },
+    set end(val: TSESTree.Position) {
+      locEnd = val;
+    },
   };
 }
 
@@ -522,6 +540,17 @@ export function getTokenType(
   return AST_TOKEN_TYPES.Identifier;
 }
 
+export type OptionalLoc<T> = Pick<T, Exclude<keyof T, 'loc'>> & {
+  loc?: TSESTree.SourceLocation;
+};
+export type OptionalRangeAndLoc<T> = Pick<
+  T,
+  Exclude<keyof T, 'loc' | 'range'>
+> & {
+  range?: TSESTree.Range;
+  loc?: TSESTree.SourceLocation;
+};
+
 /**
  * Extends and formats a given ts.Token, for a given AST
  * @param token the ts.Token
@@ -541,26 +570,27 @@ export function convertToken(
   const tokenType = getTokenType(token);
 
   if (tokenType === AST_TOKEN_TYPES.RegularExpression) {
-    return {
-      type: tokenType,
+    const newToken: TSESTree.RegularExpressionToken = {
+      type: AST_TOKEN_TYPES.RegularExpression,
       value,
       range: [start, end],
-      loc: getLocFor(start, end, ast),
       regex: {
         pattern: value.slice(1, value.lastIndexOf('/')),
         flags: value.slice(value.lastIndexOf('/') + 1),
       },
-    };
-  } else {
-    // @ts-expect-error TS is complaining about `value` not being the correct
-    // type but it is
-    return {
-      type: tokenType,
-      value,
-      range: [start, end],
       loc: getLocFor(start, end, ast),
     };
+    return newToken;
   }
+
+  // @ts-expect-error TS is complaining about `value` not being the correct type but it is
+  const newToken: Exclude<TSESTree.Token, TSESTree.RegularExpressionToken> = {
+    type: tokenType,
+    value,
+    range: [start, end],
+    loc: getLocFor(start, end, ast),
+  };
+  return newToken;
 }
 
 /**

diff --git a/packages/typescript-estree/src/simple-traverse.ts b/packages/typescript-estree/src/simple-traverse.ts
@@ -13,7 +13,8 @@ function getVisitorKeysForNode(
   node: TSESTree.Node,
 ): readonly (keyof TSESTree.Node)[] {
   const keys = allVisitorKeys[node.type];
-  return (keys ?? []) as never;
+  // @ts-expect-error -- keys will provably be of the correct type - it's just not possible to type
+  return keys ?? [];
 }
 
 type SimpleTraverseOptions =