Add a check for unused private declarations

src/main.zig

@@ -1,10 +1,10 @@
 const std = @import("std");
 const Io = std.Io;
 
-const rules = @import("rules/_list.zig");
+pub const rules = @import("rules/_list.zig");
 
 var io: Io = undefined;
-var allocator: std.mem.Allocator = undefined;
+pub var allocator: std.mem.Allocator = undefined;
 
 var failed: bool = false;
 

src/rules/_list.zig

@@ -7,3 +7,4 @@ pub const imports = @import("imports.zig");
 pub const tab_indentation = @import("tab_indentation.zig");
 pub const trailing_space = @import("trailing_space.zig");
 pub const orelse_unreachable = @import("orelse_unreachable.zig");
+pub const unused_private_decls = @import("unused_private_decls.zig");

src/rules/imports.zig

@@ -29,53 +29,54 @@ fn isAliasAllowed(_importName: []const u8, _aliasName: []const u8) bool {
 	return std.mem.eql(u8, importName, aliasName);
 }
 
+pub fn isImport(ctx: main.Context, ast: std.zig.Ast, node: std.zig.Ast.Node.Index, mode: enum { errorOnAliasNameMismatch, ignoreAliasNameMismatch }) bool {
+	if (ast.nodeTag(node) != .simple_var_decl) return false;
+	const varDec = ast.simpleVarDecl(node);
+	const aliasName = ast.tokenSlice(varDec.ast.mut_token + 1);
+	const rhsNode = varDec.ast.init_node.unwrap() orelse return false;
+
+	switch (ast.nodeTag(rhsNode)) {
+		.builtin_call_two_comma => { // @import("x",)
+			const token = ast.nodeMainToken(rhsNode);
+			const importKeyword = ast.tokenSlice(token);
+			if (!std.mem.eql(u8, importKeyword, "@import")) return false;
+			ctx.printError("@import should not have a trailing comma.", ast.tokenStart(token));
+			return true;
+		},
+		.builtin_call_two => { // @import("x")
+			const importKeyword = ast.tokenSlice(ast.nodeMainToken(rhsNode));
+			if (!std.mem.eql(u8, importKeyword, "@import")) return false;
+
+			const token = ast.nodeMainToken(ast.nodeData(rhsNode).opt_node_and_opt_node[0].unwrap().?);
+			var importName = ast.tokenSlice(token);
+			importName = importName[1 .. importName.len - 1];
+
+			if (!isAliasAllowed(importName, aliasName)) {
+				ctx.printError("Encountered import with mismatched name", ast.tokenStart(token));
+			}
+			return true;
+		},
+		.field_access => { // alias
+			const token = ast.nodeData(rhsNode).node_and_token[1];
+			const importName = ast.tokenSlice(token);
+
+			if (!isAliasAllowed(importName, aliasName)) {
+				if (mode == .ignoreAliasNameMismatch) return false;
+				ctx.printError("Encountered alias with mismatched name", ast.tokenStart(token));
+			}
+			return true;
+		},
+		else => return false,
+	}
+}
+
 pub fn check(ctx: main.Context) void {
 	const ast = ctx.ast orelse return;
 	const root = ast.rootDecls();
 	var firstNonImportNode: ?std.zig.Ast.Node.Index = null;
 
 	for (root) |node| {
-		const isImport: bool = blk: {
-			if (ast.nodeTag(node) != .simple_var_decl) break :blk false;
-			const varDec = ast.simpleVarDecl(node);
-			const aliasName = ast.tokenSlice(varDec.ast.mut_token + 1);
-			const rhsNode = varDec.ast.init_node.unwrap().?;
-
-			switch (ast.nodeTag(rhsNode)) {
-				.builtin_call_two_comma => { // @import("x",)
-					const token = ast.nodeMainToken(rhsNode);
-					const importKeyword = ast.tokenSlice(token);
-					if (!std.mem.eql(u8, importKeyword, "@import")) break :blk false;
-					ctx.printError("@import should not have a trailing comma.", ast.tokenStart(token));
-					break :blk true;
-				},
-				.builtin_call_two => { // @import("x")
-					const importKeyword = ast.tokenSlice(ast.nodeMainToken(rhsNode));
-					if (!std.mem.eql(u8, importKeyword, "@import")) break :blk false;
-
-					const token = ast.nodeMainToken(ast.nodeData(rhsNode).opt_node_and_opt_node[0].unwrap().?);
-					var importName = ast.tokenSlice(token);
-					importName = importName[1 .. importName.len - 1];
-
-					if (!isAliasAllowed(importName, aliasName)) {
-						ctx.printError("Encountered import with mismatched name", ast.tokenStart(token));
-					}
-					break :blk true;
-				},
-				.field_access => { // alias
-					const token = ast.nodeData(rhsNode).node_and_token[1];
-					const importName = ast.tokenSlice(token);
-
-					if (!isAliasAllowed(importName, aliasName)) {
-						if (firstNonImportNode != null) break :blk false;
-						ctx.printError("Encountered alias with mismatched name", ast.tokenStart(token));
-					}
-					break :blk true;
-				},
-				else => break :blk false,
-			}
-		};
-		if (isImport) {
+		if (isImport(ctx, ast, node, if (firstNonImportNode != null) .ignoreAliasNameMismatch else .errorOnAliasNameMismatch)) {
 			if (firstNonImportNode) |nonImportNode| {
 				ctx.printError("Encountered import/alias after import section", ast.tokenStart(ast.firstToken(node)));
 				ctx.printInfo("determined end of import section", ast.tokenStart(ast.firstToken(nonImportNode)));

src/rules/unused_private_decls.zig

@@ -0,0 +1,60 @@
+const std = @import("std");
+
+const main = @import("main");
+
+pub fn check(ctx: main.Context) void {
+	const ast = ctx.ast orelse return;
+
+	var identifiers: std.StringHashMapUnmanaged(void) = .empty;
+	defer identifiers.deinit(main.allocator);
+
+	for (0..ast.nodes.len) |nodeIndex| {
+		const node: std.zig.Ast.Node.Index = @enumFromInt(nodeIndex);
+		switch (ast.nodeTag(node)) {
+			.identifier => {
+				_ = identifiers.getOrPut(main.allocator, ast.getNodeSource(node)) catch @panic("OOM");
+			},
+			.field_access => {
+				const token = ast.nodeData(node).node_and_token[1];
+				const name = ast.tokenSlice(token);
+				_ = identifiers.getOrPut(main.allocator, name) catch @panic("OOM");
+			},
+			.enum_literal => {
+				const name = ast.tokenSlice(ast.nodeMainToken(node));
+				_ = identifiers.getOrPut(main.allocator, name) catch @panic("OOM");
+			},
+			else => continue,
+		}
+	}
+
+	for (0..ast.nodes.len) |nodeIndex| {
+		const node: std.zig.Ast.Node.Index = @enumFromInt(nodeIndex);
+		switch (ast.nodeTag(node)) {
+			.simple_var_decl => {
+				if (main.rules.imports.isImport(ctx, ast, node, .ignoreAliasNameMismatch)) continue;
+				const varDec = ast.simpleVarDecl(node);
+				if (varDec.visib_token != null) continue;
+				const name = ast.tokenSlice(varDec.ast.mut_token + 1);
+				if (!identifiers.contains(name)) {
+					ctx.printError("Unused declaration", ast.tokenStart(varDec.firstToken()));
+				}
+			},
+			.fn_proto, .fn_proto_simple, .fn_proto_one, .fn_proto_multi => |tag| {
+				var buffer: [1]std.zig.Ast.Node.Index = undefined;
+				const functionProto = switch (tag) {
+					.fn_proto => ast.fnProto(node),
+					.fn_proto_simple => ast.fnProtoSimple(&buffer, node),
+					.fn_proto_one => ast.fnProtoOne(&buffer, node),
+					.fn_proto_multi => ast.fnProtoMulti(node),
+					else => unreachable,
+				};
+				if (functionProto.visib_token != null) continue;
+				const name = ast.tokenSlice(functionProto.name_token orelse continue);
+				if (!identifiers.contains(name)) {
+					ctx.printError("Unused declaration", ast.tokenStart(functionProto.firstToken()));
+				}
+			},
+			else => continue,
+		}
+	}
+}