fix(eslint-plugin): [no-use-before-define] false positive for function type arguments (typescript-eslint#2554)

bradzacher · web-flow · commit 189162d46ecb · 2020-09-13T12:27:01.000-07:00
Fixes typescript-eslint#2527
diff --git a/packages/eslint-plugin/src/rules/no-use-before-define.ts b/packages/eslint-plugin/src/rules/no-use-before-define.ts
@@ -260,7 +260,8 @@ export default util.createRule<Options, MessageIds>({
           variable.identifiers.length === 0 ||
           (variable.identifiers[0].range[1] <= reference.identifier.range[1] &&
             !isInInitializer(variable, reference)) ||
-          !isForbidden(variable, reference)
+          !isForbidden(variable, reference) ||
+          reference.from.type === TSESLint.Scope.ScopeType.functionType
         ) {
           return;
         }
diff --git a/packages/eslint-plugin/tests/rules/no-use-before-define.test.ts b/packages/eslint-plugin/tests/rules/no-use-before-define.test.ts
@@ -343,6 +343,10 @@ const React = require('react');
         },
       },
     },
+    // https://github.com/typescript-eslint/typescript-eslint/issues/2527
+    `
+type T = (value: unknown) => value is Id;
+    `,
   ],
   invalid: [
     {
diff --git a/packages/experimental-utils/src/ts-eslint/Scope.ts b/packages/experimental-utils/src/ts-eslint/Scope.ts
@@ -46,9 +46,11 @@ namespace Scope {
   export type Reference = scopeManager.Reference;
   export type Variable = scopeManager.Variable | ESLintScopeVariable;
   export type Scope = scopeManager.Scope;
+  export const ScopeType = scopeManager.ScopeType;
   // TODO - in the next major, clean this up with a breaking change
   export type DefinitionType = scopeManager.Definition;
   export type Definition = scopeManager.Definition;
+  export const DefinitionType = scopeManager.DefinitionType;
 }
 
 export { Scope };
