fix: no longer removing Map or Set type when they are needed

src/shared/comparisons.ts

@@ -57,11 +57,22 @@ export const declaredInitializedTypeNodeIsRedundant = (
 		return undefined;
 	}
 
-	return declaredTypeIsEquivalent(
-		request.services.program.getTypeChecker(),
-		declaredType,
-		initializedType,
-	);
+	const typeChecker = request.services.program.getTypeChecker();
+
+	const declaredEspacedName = declaredType.getSymbol()?.getEscapedName();
+
+	// This is brute-force way to keep Map<string, number> comparison to Map without type arguments...
+	// This will allow many type declarations that could be removed.
+	if (
+		// eslint-disable-next-line @typescript-eslint/no-unsafe-enum-comparison
+		(declaredEspacedName === "Map" || declaredEspacedName === "set") &&
+		typeChecker.typeToString(declaredType) !=
+			typeChecker.typeToString(initializedType)
+	) {
+		return false;
+	}
+
+	return declaredTypeIsEquivalent(typeChecker, declaredType, initializedType);
 };
 
 const declaredTypeIsEquivalent = (

test/cases/fixes/noInferableTypes/variableDeclarations/expected.ts

@@ -46,6 +46,9 @@
 	let letInferableNullOrStrings = [null, ""];
 	let letInferableNumberOrRegExps = [0, /./];
 
+	// Non-inferable const arrays
+	const constNonInferableStringArray: string[] = [];
+
 	// Non-inferable const multi-type arrays
 	const constNonInferableNullOrStrings: (null | string)[] = [null];
 	const constNonInferableNumberOrRegExps: (number | RegExp)[] = [0];
@@ -87,7 +90,8 @@
 	// should keep their types
 	// map
 	type TypeSummariesPerNodeByName = Map<string, number>;
-	const incompleteTypes = new Map();
+	const incompleteTypes: TypeSummariesPerNodeByName = new Map();
+	const stringSet = new Set();
 	// array
 	interface Mutation {
 		readonly range: number;
@@ -102,4 +106,14 @@
 	const fixIncompleteImplicitClassGenerics: FileMutator = (
 		request: FileMutationsRequest,
 	) => undefined;
+
+	// should lose their types
+	const incompleteTypes2: TypeSummariesPerNodeByName = new Map<
+		string,
+		number
+	>();
+	const stringMapTyped = new Map<string, number>();
+	const anyMap = new Map();
+	const anySet = new Set();
+	const anyArray: any[] = [];
 })();

test/cases/fixes/noInferableTypes/variableDeclarations/original.ts

@@ -46,6 +46,9 @@
 	let letInferableNullOrStrings: (null | string)[] = [null, ""];
 	let letInferableNumberOrRegExps: (number | RegExp)[] = [0, /./];
 
+	// Non-inferable const arrays
+	const constNonInferableStringArray: string[] = [];
+
 	// Non-inferable const multi-type arrays
 	const constNonInferableNullOrStrings: (null | string)[] = [null];
 	const constNonInferableNumberOrRegExps: (number | RegExp)[] = [0];
@@ -88,6 +91,7 @@
 	// map
 	type TypeSummariesPerNodeByName = Map<string, number>;
 	const incompleteTypes: TypeSummariesPerNodeByName = new Map();
+	const stringSet: Set<string> = new Set();
 	// array
 	interface Mutation {
 		readonly range: number;
@@ -102,4 +106,14 @@
 	const fixIncompleteImplicitClassGenerics: FileMutator = (
 		request: FileMutationsRequest,
 	) => undefined;
+
+	// should lose their types
+	const incompleteTypes2: TypeSummariesPerNodeByName = new Map<
+		string,
+		number
+	>();
+	const stringMapTyped: Map<string, number> = new Map<string, number>();
+	const anyMap: Map<any, any> = new Map();
+	const anySet: Set<any> = new Set();
+	const anyArray: any[] = [];
 })();