diff --git a/lib/Dependency.js b/lib/Dependency.js
index 2f0c8fe0905..6d27b1ed6d2 100644
--- a/lib/Dependency.js
+++ b/lib/Dependency.js
@@ -18,13 +18,13 @@ const DependencyReference = require("./dependencies/DependencyReference");
  */
 
 /** @typedef {Object} SourcePosition
- *  @property {number} column
  *  @property {number} line
+ *  @property {number=} column
  */
 
 /** @typedef {Object} RealDependencyLocation
  *  @property {SourcePosition} start
- *  @property {SourcePosition} end
+ *  @property {SourcePosition=} end
  *  @property {number=} index
  */
 
diff --git a/lib/SingleEntryPlugin.js b/lib/SingleEntryPlugin.js
index e049abc2ac8..4a1703b1f85 100644
--- a/lib/SingleEntryPlugin.js
+++ b/lib/SingleEntryPlugin.js
@@ -48,9 +48,14 @@ class SingleEntryPlugin {
 		);
 	}
 
+	/**
+	 * @param {string} entry entry request
+	 * @param {string} name entry name
+	 * @returns {SingleEntryDependency} the dependency
+	 */
 	static createDependency(entry, name) {
 		const dep = new SingleEntryDependency(entry);
-		dep.loc = name;
+		dep.loc = { name };
 		return dep;
 	}
 }
diff --git a/lib/dependencies/LoaderPlugin.js b/lib/dependencies/LoaderPlugin.js
index a3ab3f14104..c781d063605 100644
--- a/lib/dependencies/LoaderPlugin.js
+++ b/lib/dependencies/LoaderPlugin.js
@@ -7,6 +7,16 @@
 const LoaderDependency = require("./LoaderDependency");
 const NormalModule = require("../NormalModule");
 
+/** @typedef {import("../Module")} Module */
+
+/**
+ * @callback LoadModuleCallback
+ * @param {Error=} err error object
+ * @param {string=} source source code
+ * @param {object=} map source map
+ * @param {Module=} module loaded module if successful
+ */
+
 class LoaderPlugin {
 	apply(compiler) {
 		compiler.hooks.compilation.tap(
@@ -23,9 +33,16 @@ class LoaderPlugin {
 			compilation.hooks.normalModuleLoader.tap(
 				"LoaderPlugin",
 				(loaderContext, module) => {
+					/**
+					 * @param {string} request the request string to load the module from
+					 * @param {LoadModuleCallback} callback callback returning the loaded module or error
+					 * @returns {void}
+					 */
 					loaderContext.loadModule = (request, callback) => {
 						const dep = new LoaderDependency(request);
-						dep.loc = request;
+						dep.loc = {
+							name: request
+						};
 						const factory = compilation.dependencyFactories.get(
 							dep.constructor
 						);
diff --git a/lib/formatLocation.js b/lib/formatLocation.js
index 8bd574d0102..f608cd496dc 100644
--- a/lib/formatLocation.js
+++ b/lib/formatLocation.js
@@ -5,57 +5,71 @@
 
 "use strict";
 
+/** @typedef {import("./Dependency").DependencyLocation} DependencyLocation */
+/** @typedef {import("./Dependency").SourcePosition} SourcePosition */
+
+// TODO webpack 5: pos must be SourcePosition
+/**
+ * @param {SourcePosition|DependencyLocation|string} pos position
+ * @returns {string} formatted position
+ */
 const formatPosition = pos => {
 	if (pos === null) return "";
-	const typeOfPos = typeof pos;
-	switch (typeOfPos) {
-		case "string":
-			return pos;
-		case "number":
-			return `${pos}`;
-		case "object":
-			if (typeof pos.line === "number" && typeof pos.column === "number") {
-				return `${pos.line}:${pos.column}`;
-			} else if (typeof pos.line === "number") {
-				return `${pos.line}:?`;
-			} else if (typeof pos.index === "number") {
-				return `+${pos.index}`;
-			} else {
-				return "";
-			}
-		default:
+	// TODO webpack 5: Simplify this
+	if (typeof pos === "string") return pos;
+	if (typeof pos === "number") return `${pos}`;
+	if (typeof pos === "object") {
+		if ("line" in pos && "column" in pos) {
+			return `${pos.line}:${pos.column}`;
+		} else if ("line" in pos) {
+			return `${pos.line}:?`;
+		} else if ("index" in pos) {
+			// TODO webpack 5 remove this case
+			return `+${pos.index}`;
+		} else {
 			return "";
+		}
 	}
+	return "";
 };
 
+// TODO webpack 5: loc must be DependencyLocation
+/**
+ * @param {DependencyLocation|SourcePosition|string} loc location
+ * @returns {string} formatted location
+ */
 const formatLocation = loc => {
 	if (loc === null) return "";
-	const typeOfLoc = typeof loc;
-	switch (typeOfLoc) {
-		case "string":
-			return loc;
-		case "number":
-			return `${loc}`;
-		case "object":
-			if (loc.start && loc.end) {
-				if (
-					typeof loc.start.line === "number" &&
-					typeof loc.end.line === "number" &&
-					typeof loc.end.column === "number" &&
-					loc.start.line === loc.end.line
-				) {
-					return `${formatPosition(loc.start)}-${loc.end.column}`;
-				} else {
-					return `${formatPosition(loc.start)}-${formatPosition(loc.end)}`;
-				}
-			}
-			if (loc.start) {
-				return formatPosition(loc.start);
+	// TODO webpack 5: Simplify this
+	if (typeof loc === "string") return loc;
+	if (typeof loc === "number") return `${loc}`;
+	if (typeof loc === "object") {
+		if ("start" in loc && loc.start && "end" in loc && loc.end) {
+			if (
+				typeof loc.start === "object" &&
+				typeof loc.start.line === "number" &&
+				typeof loc.end === "object" &&
+				typeof loc.end.line === "number" &&
+				typeof loc.end.column === "number" &&
+				loc.start.line === loc.end.line
+			) {
+				return `${formatPosition(loc.start)}-${loc.end.column}`;
+			} else {
+				return `${formatPosition(loc.start)}-${formatPosition(loc.end)}`;
 			}
-			return formatPosition(loc);
-		default:
-			return "";
+		}
+		if ("start" in loc && loc.start) {
+			return formatPosition(loc.start);
+		}
+		if ("name" in loc && "index" in loc) {
+			return `${loc.name}[${loc.index}]`;
+		}
+		if ("name" in loc) {
+			return loc.name;
+		}
+		return formatPosition(loc);
 	}
+	return "";
 };
 
 module.exports = formatLocation;