Disallow numbers as from targets

src/parser.ts

       return args;
     }
 
-    const from =
-      this.currentToken().kind === TokenKind.FROM ? this.from() : null;
+    const currentToken = this.currentToken();
+    const from = currentToken.kind === TokenKind.FROM ? this.from() : null;
     if (isError(from)) {
       return from;
     }
 
   private from(): AST.Secondary | Error {
     this.eat(TokenKind.FROM);
-    return this.alias();
+    return this.alias(this.identifier);
   }
 
-  private alias(): AST.Secondary | Error {
-    const primary = this.primary();
+  private alias(fn: () => AST.Primary | Error = this.primary): AST.Secondary | Error {
+    const primary = fn.bind(this)();
     if (isError(primary)) {
       return primary;
     }
       return token;
     }
 
-    return new Error(`Unexpected token ${token}`, token.line);
+    const repr = `{ kind: ${token.kind}${token.value ? `, value: ${token.value} }` : ""}`;
+
+    return new Error(`Unexpected token: ${repr}`, token.line);
   }
 
   private currentToken(): Token {

test/parser.test.ts

       }),
     ]);
   });
+
+  it("should not allow a number as a from target", () => {
+    const fn = () => parse("select 1 from 2");
+    expect(fn).to.throw("Unexpected token: { kind: NUMBER, value: 2 }");
+  });
 });