Minor changes

- Refactor Constructor to IdentifierAlt
 - Make () -> a unify with a

src/checker.ts

@@ -9,7 +9,7 @@ import {
 } from "./cst";
 import { ArityMismatchDiagnostic, BindingNotFoudDiagnostic, Diagnostics, UnificationFailedDiagnostic } from "./diagnostics";
 import { assert } from "./util";
-import { LabeledDirectedHashGraph, LabeledGraph, strongconnect, toposort } from "yagl"
+import { LabeledDirectedHashGraph, LabeledGraph, strongconnect } from "yagl"
 
 export enum TypeKind {
   Arrow,
@@ -1001,6 +1001,14 @@ export class Checker {
       return success;
     }
 
+    if (left.kind === TypeKind.Arrow && left.paramTypes.length === 0) {
+      return this.unify(left.returnType, right, solution);
+    }
+
+    if (right.kind === TypeKind.Arrow) {
+      return this.unify(right, left, solution);
+    }
+
     if (left.kind === TypeKind.Con && right.kind === TypeKind.Con) {
       if (left.id !== right.id) {
         return false;

src/cst.ts

@@ -69,7 +69,7 @@ export const enum SyntaxKind {
 
   // Tokens
   Identifier,
-  Constructor,
+  IdentifierAlt,
   CustomOperator,
   Assignment,
   LParen,
@@ -207,6 +207,7 @@ export class Scope {
       if (isNodeWithScope(curr)) {
         return curr.getScope();
       }
+      curr = curr.parent;
     }
     return null;
   }
@@ -502,9 +503,9 @@ export class StringLiteral extends TokenBase {
 
 }
 
-export class Constructor extends TokenBase {
+export class IdentifierAlt extends TokenBase {
 
-  public readonly kind = SyntaxKind.Constructor;
+  public readonly kind = SyntaxKind.IdentifierAlt;
 
   public constructor(
     public text: string,
@@ -792,7 +793,7 @@ export type Token
   | LBracket
   | RBracket
   | Identifier
-  | Constructor
+  | IdentifierAlt
   | CustomOperator
   | Integer
   | StringLiteral
@@ -828,7 +829,7 @@ export class ReferenceTypeExpression extends SyntaxBase {
 
   public constructor(
     public modulePath: Array<[Identifier, Dot]>,
-    public name: Identifier,
+    public name: IdentifierAlt,
   ) {
     super();
   }
@@ -900,7 +901,7 @@ export class NamedTuplePattern extends SyntaxBase {
   public readonly kind = SyntaxKind.NamedTuplePattern;
 
   public constructor(
-    public name: Constructor,
+    public name: IdentifierAlt,
     public elements: Pattern[],
   ) {
     super();
@@ -995,7 +996,7 @@ export class StructPattern extends SyntaxBase {
   public readonly kind = SyntaxKind.StructPattern;
 
   public constructor(
-    public name: Constructor,
+    public name: IdentifierAlt,
     public lbrace: LBrace,
     public elements: StructPatternElement[],
     public rbrace: RBrace,
@@ -1205,7 +1206,7 @@ export class StructExpression extends SyntaxBase {
   public readonly kind = SyntaxKind.StructExpression;
 
   public constructor(
-    public name: Constructor,
+    public name: IdentifierAlt,
     public lbrace: LBrace,
     public elements: StructExpressionElement[],
     public rbrace: RBrace,
@@ -1228,7 +1229,7 @@ export class NamedTupleExpression extends SyntaxBase {
   public readonly kind = SyntaxKind.NamedTupleExpression;
 
   public constructor(
-    public name: Constructor,
+    public name: IdentifierAlt,
     public elements: Expression[],
   ) {
     super();

src/parser.ts

@@ -156,17 +156,17 @@ export class Parser {
   }
 
   public parseReferenceTypeExpression(): ReferenceTypeExpression {
-    const name = this.expectToken(SyntaxKind.Identifier);
+    const name = this.expectToken(SyntaxKind.IdentifierAlt);
     return new ReferenceTypeExpression([], name);
   }
 
   public parseTypeExpression(): TypeExpression {
     const t0 = this.peekToken();
     switch (t0.kind) {
-      case SyntaxKind.Identifier:
+      case SyntaxKind.IdentifierAlt:
         return this.parseReferenceTypeExpression();
       default:
-        this.raiseParseError(t0, [ SyntaxKind.Identifier ]);
+        this.raiseParseError(t0, [ SyntaxKind.IdentifierAlt ]);
     }
   }
 
@@ -218,7 +218,7 @@ export class Parser {
         return this.parseExpressionWithParens();
       case SyntaxKind.Identifier:
         return this.parseReferenceExpression();
-      case SyntaxKind.Constructor:
+      case SyntaxKind.IdentifierAlt:
       {
         this.getToken();
         const t1 = this.peekToken();
@@ -384,7 +384,7 @@ export class Parser {
   }
 
   private parsePatternStartingWithConstructor() {
-    const name = this.expectToken(SyntaxKind.Constructor);
+    const name = this.expectToken(SyntaxKind.IdentifierAlt);
     const t2 = this.peekToken();
     if (t2.kind === SyntaxKind.LBrace) {
       this.getToken();
@@ -467,7 +467,7 @@ export class Parser {
       {
         this.getToken();
         const t1 = this.peekToken();
-        if (t1.kind === SyntaxKind.Constructor) {
+        if (t1.kind === SyntaxKind.IdentifierAlt) {
           return this.parsePatternStartingWithConstructor();
         } else {
           return this.parseTuplePattern();

src/scanner.ts

@@ -25,7 +25,7 @@ import {
   RBracket,
   ReturnKeyword,
   CustomOperator,
-  Constructor,
+  IdentifierAlt,
   Integer,
   TextFile,
   Dot,
@@ -353,7 +353,7 @@ export class Scanner extends BufferedStream<Token> {
             case 'elif': return new ElifKeyword(startPos);
             default:
               if (isUpper(text[0])) {
-                return new Constructor(text, startPos);
+                return new IdentifierAlt(text, startPos);
               } else {
                 return new Identifier(text, startPos);
               }