Add symbol-string shorthand syntax for maps

Author: MatheusRich

CHANGELOG.md

@@ -1,5 +1,16 @@
 ## Unreleased - [Full diff](https://github.com/lit-lang/lit/compare/v0.2.0...main)
 
+- Add symbol-string shorthand syntax for maps
+
+```lit
+let user = {
+  name: "Alice",
+}
+
+# same as { "name": "Alice" }
+# or even { :name : "Alice" }
+```
+
 - Allow break to return a value
 
 ```lit

spec/e2e/map.lit

@@ -27,6 +27,6 @@ m2[1.0] = 3
 println(m3) # expect: {"key" : 1, 1.0 : 2}
 
 # merging overwrites same keys
-println(m3.merge({"key" : 2})) # expect: {"key" : 2, 1.0 : 2}
+println(m3.merge({key: 2})) # expect: {"key" : 2, 1.0 : 2}
 
 m.merge(1) # error: [line 32] Runtime error: I was expecting a Map, but got Integer.

src/lit/parser.cr

@@ -545,8 +545,12 @@ module Lit
 
       loop do
         ignore_newlines
-        key = expression
-        consume(TokenType::COLON, "I was expecting a ':' after a map key.")
+        if match?(TokenType::SYMBOL)
+          key = Expr::Literal.new(previous.literal)
+        else
+          key = expression
+          consume(TokenType::COLON, "I was expecting a ':' after a map key.")
+        end
         value = expression
         ignore_newlines
 

src/lit/scanner.cr

@@ -294,9 +294,14 @@ module Lit
       end
 
       text = @src[@token_start_pos...@current_pos]
-      type = keyword_from(text) || TokenType::IDENTIFIER
 
-      add_token(type)
+      if peek == ':' # symbol-like string shortcut for maps
+        advance
+        add_token(TokenType::SYMBOL, text)
+      else
+        type = keyword_from(text) || TokenType::IDENTIFIER
+        add_token(type)
+      end
     end
 
     private def peek : Char

src/lit/token_type.cr

@@ -14,7 +14,7 @@ module Lit
     PIPE_GREATER
 
     # Literals
-    NUMBER; STRING; IDENTIFIER; STRING_INTERPOLATION
+    NUMBER; STRING; IDENTIFIER; STRING_INTERPOLATION; SYMBOL
 
     # Keywords
     AND; DO; ELSE; FALSE; FN; IF; VAR; LET; NIL; OR; PRINT; PRINTLN; RETURN; TRUE; TYPE; SELF; WHILE; UNTIL; LOOP; BREAK; NEXT