🤖 Pick PR #58514 (Fixed a regression with reporting u...) into release-5.5 (#58841)

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

Author: TypeScript Bot

src/compiler/utilities.ts

@@ -11439,7 +11439,7 @@ export function createNameResolver({
                     }
                     break;
             }
-            if (isSelfReferenceLocation(location)) {
+            if (isSelfReferenceLocation(location, lastLocation)) {
                 lastSelfReferenceLocation = location;
             }
             lastLocation = location;
@@ -11573,15 +11573,18 @@ export function createNameResolver({
     }
 
     type SelfReferenceLocation =
+        | ParameterDeclaration
         | FunctionDeclaration
         | ClassDeclaration
         | InterfaceDeclaration
         | EnumDeclaration
         | TypeAliasDeclaration
         | ModuleDeclaration;
 
-    function isSelfReferenceLocation(node: Node): node is SelfReferenceLocation {
+    function isSelfReferenceLocation(node: Node, lastLocation: Node | undefined): node is SelfReferenceLocation {
         switch (node.kind) {
+            case SyntaxKind.Parameter:
+                return !!lastLocation && lastLocation === (node as ParameterDeclaration).name;
             case SyntaxKind.FunctionDeclaration:
             case SyntaxKind.ClassDeclaration:
             case SyntaxKind.InterfaceDeclaration:

tests/baselines/reference/noUnusedLocals_potentialPredicateUnusedParam.errors.txt

@@ -0,0 +1,10 @@
+noUnusedLocals_potentialPredicateUnusedParam.ts(1,40): error TS6133: 'a' is declared but its value is never read.
+
+
+==== noUnusedLocals_potentialPredicateUnusedParam.ts (1 errors) ====
+    function potentialPredicateUnusedParam(a: unknown) {
+                                           ~
+!!! error TS6133: 'a' is declared but its value is never read.
+      return !!Math.random();
+    }
+    

tests/baselines/reference/noUnusedLocals_potentialPredicateUnusedParam.symbols

@@ -0,0 +1,13 @@
+//// [tests/cases/compiler/noUnusedLocals_potentialPredicateUnusedParam.ts] ////
+
+=== noUnusedLocals_potentialPredicateUnusedParam.ts ===
+function potentialPredicateUnusedParam(a: unknown) {
+>potentialPredicateUnusedParam : Symbol(potentialPredicateUnusedParam, Decl(noUnusedLocals_potentialPredicateUnusedParam.ts, 0, 0))
+>a : Symbol(a, Decl(noUnusedLocals_potentialPredicateUnusedParam.ts, 0, 39))
+
+  return !!Math.random();
+>Math.random : Symbol(Math.random, Decl(lib.es5.d.ts, --, --))
+>Math : Symbol(Math, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>random : Symbol(Math.random, Decl(lib.es5.d.ts, --, --))
+}
+

tests/baselines/reference/noUnusedLocals_potentialPredicateUnusedParam.types

@@ -0,0 +1,24 @@
+//// [tests/cases/compiler/noUnusedLocals_potentialPredicateUnusedParam.ts] ////
+
+=== noUnusedLocals_potentialPredicateUnusedParam.ts ===
+function potentialPredicateUnusedParam(a: unknown) {
+>potentialPredicateUnusedParam : (a: unknown) => boolean
+>                              : ^ ^^       ^^^^^^^^^^^^
+>a : unknown
+>  : ^^^^^^^
+
+  return !!Math.random();
+>!!Math.random() : boolean
+>                : ^^^^^^^
+>!Math.random() : boolean
+>               : ^^^^^^^
+>Math.random() : number
+>              : ^^^^^^
+>Math.random : () => number
+>            : ^^^^^^      
+>Math : Math
+>     : ^^^^
+>random : () => number
+>       : ^^^^^^      
+}
+

tests/cases/compiler/noUnusedLocals_potentialPredicateUnusedParam.ts

@@ -0,0 +1,8 @@
+// @strict: true
+// @noEmit: true
+// @noUnusedLocals: true
+// @noUnusedParameters: true
+
+function potentialPredicateUnusedParam(a: unknown) {
+  return !!Math.random();
+}