fix: crash in @typescript-eslint/no-misused-promises rule (#236)

* fix: crash in
`@typescript-eslint/no-misused-promises` rule

* Create ninety-cheetahs-remain.md

Author: ota-meshi

Diff for: .changeset/ninety-cheetahs-remain.md

@@ -0,0 +1,5 @@
+---
+"svelte-eslint-parser": patch
+---
+
+fix: crash in `@typescript-eslint/no-misused-promises` rule

Diff for: docs/internal-mechanism.md

@@ -157,14 +157,22 @@ Parse the following virtual script code as a script:
 
 export let foo: { bar: number } | null = null
 
-$: function $_reactiveStatementScopeFunction1(){console.log(foo && foo.bar);}
+$: function $_reactiveStatementScopeFunction1(){
+    console.log(foo && foo.bar);
+}
 
-$: let r = $_reactiveVariableScopeFunction2();
-function $_reactiveVariableScopeFunction2(){return foo && foo.bar;}
+$: let r =$_reactiveVariableScopeFunction2();
+function $_reactiveVariableScopeFunction2(){
+    let $_tmpVar3;
+    return ($_tmpVar3 =  foo && foo.bar);
+}
 
-$: let { bar: n } = $_reactiveVariableScopeFunction3();
-function $_reactiveVariableScopeFunction3(){return foo || { bar: 42 };}
-;function $_render4(){        
+$: let { bar: n } =$_reactiveVariableScopeFunction4();
+function $_reactiveVariableScopeFunction4(){
+    let $_tmpVar5;
+    return ($_tmpVar5 =  foo || { bar: 42 });
+}
+;function $_render6(){        
 
 (foo && foo.bar);
 }

Diff for: src/parser/typescript/analyze/index.ts

@@ -231,15 +231,15 @@ function transformForDeclareReactiveVar(
   //
   //  To:
   //  $: let id = fn()
-  //  function fn () { return x + y; }
+  //  function fn () { let tmp; return (tmp = x + y); }
   //
   //
   //  From:
   //  $: ({id} = foo);
   //
   //  To:
   //  $: let {id} = fn()
-  //  function fn () { return foo; }
+  //  function fn () { let tmp; return (tmp = foo); }
 
   /**
    * The opening paren tokens for
@@ -297,6 +297,7 @@ function transformForDeclareReactiveVar(
   }
 
   const functionId = ctx.generateUniqueId("reactiveVariableScopeFunction");
+  const tmpVarId = ctx.generateUniqueId("tmpVar");
   for (const token of openParens) {
     ctx.appendOriginal(token.range[0]);
     ctx.skipOriginalOffset(token.range[1] - token.range[0]);
@@ -306,7 +307,7 @@ function transformForDeclareReactiveVar(
   ctx.appendVirtualScript("let ");
   ctx.appendOriginal(eq ? eq.range[1] : expression.right.range[0]);
   ctx.appendVirtualScript(
-    `${functionId}();\nfunction ${functionId}(){return (`
+    `${functionId}();\nfunction ${functionId}(){let ${tmpVarId};return (${tmpVarId} = `
   );
   ctx.appendOriginal(expression.right.range[1]);
   ctx.appendVirtualScript(`)`);
@@ -347,46 +348,61 @@ function transformForDeclareReactiveVar(
       !fnDecl ||
       fnDecl.type !== "FunctionDeclaration" ||
       fnDecl.id.name !== functionId ||
-      fnDecl.body.body.length !== 1 ||
-      fnDecl.body.body[0].type !== "ReturnStatement"
+      fnDecl.body.body.length !== 2 ||
+      fnDecl.body.body[0].type !== "VariableDeclaration" ||
+      fnDecl.body.body[1].type !== "ReturnStatement"
     ) {
       return false;
     }
-    const returnStatement = fnDecl.body.body[0];
-    if (returnStatement.argument?.type !== expression.right.type) {
+    const tmpVarDeclaration = fnDecl.body.body[0];
+    if (
+      tmpVarDeclaration.declarations.length !== 1 ||
+      tmpVarDeclaration.declarations[0].type !== "VariableDeclarator"
+    ) {
       return false;
     }
+    const tempVarDeclId = tmpVarDeclaration.declarations[0].id;
+    if (
+      tempVarDeclId.type !== "Identifier" ||
+      tempVarDeclId.name !== tmpVarId
+    ) {
+      return false;
+    }
+    const returnStatement = fnDecl.body.body[1];
+    const assignment = returnStatement.argument;
+    if (
+      assignment?.type !== "AssignmentExpression" ||
+      assignment.left.type !== "Identifier" ||
+      assignment.right.type !== expression.right.type
+    ) {
+      return false;
+    }
+    const tempLeft = assignment.left;
     // Remove function declaration
     program.body.splice(nextIndex, 1);
     // Restore expression statement
-    const newExpression: TSESTree.AssignmentExpression = {
-      type: "AssignmentExpression" as TSESTree.AssignmentExpression["type"],
-      operator: "=",
-      left: idDecl.id,
-      right: returnStatement.argument,
-      loc: {
-        start: idDecl.id.loc.start,
-        end: expressionCloseParen
-          ? expressionCloseParen.loc.end
-          : returnStatement.argument.loc.end,
-      },
-      range: [
-        idDecl.id.range[0],
-        expressionCloseParen
-          ? expressionCloseParen.range[1]
-          : returnStatement.argument.range[1],
-      ],
+    assignment.left = idDecl.id;
+    assignment.loc = {
+      start: idDecl.id.loc.start,
+      end: expressionCloseParen
+        ? expressionCloseParen.loc.end
+        : assignment.right.loc.end,
     };
-    idDecl.id.parent = newExpression;
-    returnStatement.argument.parent = newExpression;
+    assignment.range = [
+      idDecl.id.range[0],
+      expressionCloseParen
+        ? expressionCloseParen.range[1]
+        : assignment.right.range[1],
+    ];
+    idDecl.id.parent = assignment;
     const newBody: TSESTree.ExpressionStatement = {
       type: "ExpressionStatement" as TSESTree.ExpressionStatement["type"],
-      expression: newExpression,
+      expression: assignment,
       loc: statement.body.loc,
       range: statement.body.range,
       parent: reactiveStatement,
     };
-    newExpression.parent = newBody;
+    assignment.parent = newBody;
     reactiveStatement.body = newBody;
     // Restore statement end location
     reactiveStatement.range[1] = returnStatement.range[1];
@@ -401,12 +417,20 @@ function transformForDeclareReactiveVar(
     );
 
     const scopeManager = result.scopeManager as ScopeManager;
+    removeAllScopeAndVariableAndReference(tmpVarDeclaration, {
+      visitorKeys: result.visitorKeys,
+      scopeManager,
+    });
     removeFunctionScope(fnDecl, scopeManager);
+
     const scope = getProgramScope(scopeManager);
     for (const reference of getAllReferences(idDecl.id, scope)) {
-      reference.writeExpr = newExpression.right as ESTree.Expression;
+      reference.writeExpr = assignment.right as ESTree.Expression;
     }
 
+    removeIdentifierReference(tempLeft, scope);
+    removeIdentifierVariable(tempVarDeclId, scope);
+
     removeIdentifierReference(idDecl.init.callee, scope);
     removeIdentifierVariable(idDecl.id, scope);
     return true;

Diff for: tests/fixtures/integrations/type-info-tests/ts-no-misused-promises-input.svelte

@@ -0,0 +1,5 @@
+<script lang="ts">
+$: noMisusedPromisesvar = 42;
+</script>
+
+{noMisusedPromisesvar}

Diff for: tests/fixtures/integrations/type-info-tests/ts-no-misused-promises-output.json

@@ -0,0 +1 @@
+[]

Diff for: tests/fixtures/integrations/type-info-tests/ts-no-misused-promises-setup.ts

@@ -0,0 +1,24 @@
+/* eslint eslint-comments/require-description: 0, @typescript-eslint/explicit-module-boundary-types: 0 */
+import type { Linter } from "eslint";
+import { BASIC_PARSER_OPTIONS } from "../../../src/parser/test-utils";
+import { rules } from "@typescript-eslint/eslint-plugin";
+export function setupLinter(linter: Linter) {
+  linter.defineRule(
+    "@typescript-eslint/no-misused-promises",
+    rules["no-misused-promises"] as never
+  );
+}
+
+export function getConfig() {
+  return {
+    parser: "svelte-eslint-parser",
+    parserOptions: BASIC_PARSER_OPTIONS,
+    rules: {
+      "@typescript-eslint/no-misused-promises": "error",
+    },
+    env: {
+      browser: true,
+      es2021: true,
+    },
+  };
+}