Give some love to the linter

src/ast.ts

@@ -119,7 +119,7 @@ export abstract class Node {
 
   static createOmittedType(
     range: Range
-  ) {
+  ): TypeNode {
     return Node.createType(
       Node.createIdentifierExpression("", range),
       null,

src/compiler.ts

@@ -1892,7 +1892,11 @@ export class Compiler extends DiagnosticEmitter {
     return expr;
   }
 
-  compileExpressionRetainType(expression: Expression, contextualType: Type, wrapSmallIntegers: bool = true) {
+  compileExpressionRetainType(
+    expression: Expression,
+    contextualType: Type,
+    wrapSmallIntegers: bool = true
+  ): ExpressionRef {
     return this.compileExpression(
       expression,
       contextualType == Type.void

src/decompiler.ts

@@ -27,7 +27,7 @@ export class Decompiler {
   constructor() { }
 
   /** Decompiles a module to an AST that can then be serialized. */
-  decompile(module: Module) {
+  decompile(module: Module): void {
     throw new Error("not implemented");
   }
 

src/diagnostics.ts

@@ -215,7 +215,7 @@ export abstract class DiagnosticEmitter {
     arg0: string | null = null,
     arg1: string | null = null,
     arg2: string | null = null
-  ) {
+  ): void {
     var message = DiagnosticMessage.create(code, category, arg0, arg1, arg2).withRange(range);
     this.diagnostics.push(message);
     // console.log(formatDiagnosticMessage(message, true, true) + "\n"); // temporary

src/module.ts

@@ -223,7 +223,7 @@ export class MemorySegment {
   buffer: Uint8Array;
   offset: I64;
 
-  static create(buffer: Uint8Array, offset: I64) {
+  static create(buffer: Uint8Array, offset: I64): MemorySegment {
     var segment = new MemorySegment();
     segment.buffer = buffer;
     segment.offset = offset;

src/program.ts

@@ -612,7 +612,7 @@ export class Program extends DiagnosticEmitter {
     decorators: DecoratorNode[] | null,
     prototype: FunctionPrototype,
     classPrototype: ClassPrototype
-  ) {
+  ): void {
     // handle operator annotations. operators are either instance methods taking
     // a second argument of the instance's type or static methods taking two
     // arguments of the instance's type. return values vary depending on the