Semicolon as statement ender

README.md

@@ -34,7 +34,7 @@ npm run mtsc ./tests/singleVar.ts
 ## Exercises
 
 - [x] Add EmptyStatement (https://github.com/imteekay/mini-typescript/pull/2).
-- [ ] Make semicolon a statement ender, not statement separator.
+- [x] Make semicolon a statement ender, not statement separator.
   - Hint: You'll need a predicate to peek at the next token and decide if it's the start of an element.
   - Bonus: Switch from semicolon to newline as statement ender.
 - [x] Add string literals (https://github.com/imteekay/mini-typescript/pull/4).

baselines/reference/emptyStatement.tree.baseline

@@ -48,7 +48,7 @@
       }
     },
     {
-      "kind": "EmptyStatement"
+      "kind": "EndOfFile"
     }
   ]
 }

baselines/reference/redeclare.tree.baseline

@@ -31,7 +31,7 @@
       }
     },
     {
-      "kind": "EmptyStatement"
+      "kind": "EndOfFile"
     }
   ]
 }

baselines/reference/singleIdentifier.tree.baseline

@@ -9,7 +9,7 @@
       }
     },
     {
-      "kind": "EmptyStatement"
+      "kind": "EndOfFile"
     }
   ]
 }

baselines/reference/singleTypedVar.tree.baseline

@@ -46,7 +46,7 @@
       }
     },
     {
-      "kind": "EmptyStatement"
+      "kind": "EndOfFile"
     }
   ]
 }

baselines/reference/singleVar.tree.baseline

@@ -20,7 +20,7 @@
       }
     },
     {
-      "kind": "EmptyStatement"
+      "kind": "EndOfFile"
     }
   ]
 }

baselines/reference/stringLiteral.tree.baseline

@@ -147,7 +147,7 @@
       }
     },
     {
-      "kind": "EmptyStatement"
+      "kind": "EndOfFile"
     }
   ]
 }

baselines/reference/terminator.errors.baseline

@@ -0,0 +1 @@
+[]

baselines/reference/terminator.js.baseline

@@ -0,0 +1 @@
+"var x = 1;\nvar y = 2;\nvar z = 3;\nx;\ny;\nz"

baselines/reference/terminator.tree.baseline

@@ -0,0 +1,81 @@
+{
+  "locals": {
+    "x": [
+      {
+        "kind": "Var",
+        "pos": 3
+      }
+    ],
+    "y": [
+      {
+        "kind": "Var",
+        "pos": 14
+      }
+    ],
+    "z": [
+      {
+        "kind": "Var",
+        "pos": 25
+      }
+    ]
+  },
+  "statements": [
+    {
+      "kind": "Var",
+      "name": {
+        "kind": "Identifier",
+        "text": "x"
+      },
+      "init": {
+        "kind": "NumericLiteral",
+        "value": 1
+      }
+    },
+    {
+      "kind": "Var",
+      "name": {
+        "kind": "Identifier",
+        "text": "y"
+      },
+      "init": {
+        "kind": "NumericLiteral",
+        "value": 2
+      }
+    },
+    {
+      "kind": "Var",
+      "name": {
+        "kind": "Identifier",
+        "text": "z"
+      },
+      "init": {
+        "kind": "NumericLiteral",
+        "value": 3
+      }
+    },
+    {
+      "kind": "ExpressionStatement",
+      "expr": {
+        "kind": "Identifier",
+        "text": "x"
+      }
+    },
+    {
+      "kind": "ExpressionStatement",
+      "expr": {
+        "kind": "Identifier",
+        "text": "y"
+      }
+    },
+    {
+      "kind": "ExpressionStatement",
+      "expr": {
+        "kind": "Identifier",
+        "text": "z"
+      }
+    },
+    {
+      "kind": "EndOfFile"
+    }
+  ]
+}

baselines/reference/twoStatements.tree.baseline

@@ -34,7 +34,7 @@
       }
     },
     {
-      "kind": "EmptyStatement"
+      "kind": "EndOfFile"
     }
   ]
 }

baselines/reference/twoTypedStatements.tree.baseline

@@ -38,7 +38,7 @@
       }
     },
     {
-      "kind": "EmptyStatement"
+      "kind": "EndOfFile"
     }
   ]
 }

baselines/reference/typeAlias.tree.baseline

@@ -194,7 +194,7 @@
       }
     },
     {
-      "kind": "EmptyStatement"
+      "kind": "EndOfFile"
     }
   ]
 }

src/check.ts

@@ -14,6 +14,7 @@ const stringType: Type = { id: 'string' };
 const numberType: Type = { id: 'number' };
 const errorType: Type = { id: 'error' };
 const empty: Type = { id: 'empty' };
+const eof: Type = { id: 'eof' };
 
 function typeToString(type: Type) {
   return type.id;
@@ -44,6 +45,8 @@ export function check(module: Module) {
         return checkType(statement.typename);
       case Node.EmptyStatement:
         return empty;
+      case Node.EndOfFile:
+        return eof;
     }
   }
 

src/emit.ts

@@ -34,6 +34,8 @@ function emitStatement(statement: Statement): string {
       return `type ${statement.name.text} = ${statement.typename.text}`;
     case Node.EmptyStatement:
       return '';
+    case Node.EndOfFile:
+      return '';
   }
 }
 

src/lex.ts

@@ -22,21 +22,17 @@ export function lex(s: string): Lexer {
   };
 
   function scan() {
-    // scan forward all
-    // \t - tabs
-    // \b - empty strings at the beginning and end of a word
-    // \n - newline char
-    scanForward((c) => /[ \t\b\n]/.test(c));
+    scanForward(isEmptyStrings);
     const start = pos;
 
     if (pos === s.length) {
       token = Token.EOF;
     } else if (/[0-9]/.test(s.charAt(pos))) {
-      scanForward((c) => /[0-9]/.test(c));
+      scanForward(isNumber);
       text = s.slice(start, pos);
       token = Token.NumericLiteral;
     } else if (/[_a-zA-Z]/.test(s.charAt(pos))) {
-      scanForward((c) => /[_a-zA-Z0-9]/.test(c));
+      scanForward(isAlphanumerical);
       text = s.slice(start, pos);
       token =
         text in keywords
@@ -65,6 +61,22 @@ export function lex(s: string): Lexer {
     }
   }
 
+  function isEmptyStrings(c: string) {
+    // scan forward all
+    // \t - tabs
+    // \b - empty strings at the beginning and end of a word
+    // \n - newline char
+    return /[ \t\b\n]/.test(c);
+  }
+
+  function isNumber(c: string) {
+    return /[0-9]/.test(c);
+  }
+
+  function isAlphanumerical(c: string) {
+    return /[_a-zA-Z0-9]/.test(c);
+  }
+
   function scanForward(pred: (x: string) => boolean) {
     while (pos < s.length && pred(s.charAt(pos))) pos++;
   }

src/parse.ts

@@ -9,18 +9,15 @@ import {
 } from './types';
 import { error } from './error';
 
-const emptyTokens = [Token.EOF, Token.Semicolon];
-
 export function parse(lexer: Lexer): Module {
   lexer.scan();
   return parseModule();
 
   function parseModule(): Module {
-    const statements = parseSeparated(parseStatement, () =>
-      tryParseToken(Token.Semicolon),
-    );
-    parseExpected(Token.EOF);
-    return { statements, locals: new Map() };
+    return {
+      statements: parseStatements(parseStatement),
+      locals: new Map(),
+    };
   }
 
   function parseExpression(): Expression {
@@ -65,7 +62,10 @@ export function parse(lexer: Lexer): Module {
 
   function parseStatement(): Statement {
     const pos = lexer.pos();
-    if (tryParseToken(Token.Var)) {
+
+    if (tryParseToken(Token.EOF)) {
+      return { kind: Node.EndOfFile };
+    } else if (tryParseToken(Token.Var)) {
       const name = parseIdentifier();
       const typename = tryParseToken(Token.Colon)
         ? parseIdentifier()
@@ -78,8 +78,13 @@ export function parse(lexer: Lexer): Module {
       parseExpected(Token.Equals);
       const typename = parseIdentifier();
       return { kind: Node.TypeAlias, name, typename, pos };
-    } else if (emptyTokens.includes(lexer.token())) {
-      return { kind: Node.EmptyStatement };
+    } else if (tryParseToken(Token.Semicolon)) {
+      // if a semicolon is followed by another semicolon,
+      // it should return an empty statement
+      if (lexer.token() === Token.Semicolon) {
+        return { kind: Node.EmptyStatement };
+      }
+      return parseStatement();
     }
     return { kind: Node.ExpressionStatement, expr: parseExpression(), pos };
   }
@@ -103,9 +108,9 @@ export function parse(lexer: Lexer): Module {
     }
   }
 
-  function parseSeparated<T>(element: () => T, separator: () => unknown) {
+  function parseStatements<T>(element: () => T) {
     const list = [element()];
-    while (separator()) {
+    while (lexer.token() !== Token.EOF) {
       list.push(element());
     }
     return list;

src/transform.ts

@@ -18,6 +18,8 @@ function typescript(statements: Statement[]) {
         return [];
       case Node.EmptyStatement:
         return [];
+      case Node.EndOfFile:
+        return [];
     }
   }
 }

src/types.ts

@@ -33,6 +33,7 @@ export enum Node {
   TypeAlias,
   StringLiteral,
   EmptyStatement,
+  EndOfFile,
 }
 
 export type Error = {
@@ -72,7 +73,12 @@ export type Assignment = Location & {
   value: Expression;
 };
 
-export type Statement = ExpressionStatement | Var | TypeAlias | EmptyStatement;
+export type Statement =
+  | ExpressionStatement
+  | Var
+  | TypeAlias
+  | EmptyStatement
+  | EndOfFile;
 
 export type ExpressionStatement = Location & {
   kind: Node.ExpressionStatement;
@@ -96,6 +102,10 @@ export type EmptyStatement = {
   kind: Node.EmptyStatement;
 };
 
+export type EndOfFile = {
+  kind: Node.EndOfFile;
+};
+
 export type Declaration = Var | TypeAlias; // plus others, like function
 
 export type Symbol = {

tests/terminator.ts

@@ -0,0 +1,4 @@
+var x = 1;
+var y = 2;
+var z = 3;
+x;y;z;