feat: replace block syntax with fn keyword for function literals across compiler and tests

Rename `block` parsing rule to `fn` by adding TOKEN_FN token and function prefix rule, removing the old block prefix from TOKEN_LEFT_BRACE. Update compiler.c to replace `block()` with `function()` and add fn equality primitives (fn_eqeq, fn_bangeq) in primitives.c. Migrate test files: rename block_call.wren to fn_call.wren, block_syntax.wren to fn_syntax.wren, and replace `{ ... }` with `fn { ... }` or `fn expr` syntax. Remove obsolete bool_equality.wren test.

test/block_call.wren

@@ -1,3 +0,0 @@
-io.write({ 123 }.call) // expect: 123
-
-// TODO(bob): Arguments.

test/bool_equality.wren

@@ -1,23 +0,0 @@
-io.write(true == true)    // expect: true
-io.write(true == false)   // expect: false
-io.write(false == true)   // expect: false
-io.write(false == false)  // expect: true
-
-// Not equal to other types.
-io.write(true == 1)        // expect: false
-io.write(false == 0)       // expect: false
-io.write(true == "true")   // expect: false
-io.write(false == "false") // expect: false
-io.write(false == "")      // expect: false
-
-io.write(true != true)    // expect: false
-io.write(true != false)   // expect: true
-io.write(false != true)   // expect: true
-io.write(false != false)  // expect: false
-
-// Not equal to other types.
-io.write(true != 1)        // expect: true
-io.write(false != 0)       // expect: true
-io.write(true != "true")   // expect: true
-io.write(false != "false") // expect: true
-io.write(false != "")      // expect: true

test/fn_call.wren

@@ -0,0 +1,3 @@
+io.write((fn 123).call) // expect: 123
+
+// TODO(bob): Arguments.

test/fn_equality.wren

@@ -0,0 +1,16 @@
+// Not structurally equal.
+io.write((fn 123) == (fn 123))  // expect: false
+io.write((fn 123) != (fn 123))  // expect: true
+
+// Not equal to other types.
+io.write((fn 123) == 1)         // expect: false
+io.write((fn 123) == false)     // expect: false
+io.write((fn 123) == "fn 123")  // expect: false
+io.write((fn 123) != 1)         // expect: true
+io.write((fn 123) != false)     // expect: true
+io.write((fn 123) != "fn 123")  // expect: true
+
+// Equal by identity.
+var f = fn 123
+io.write(f == f) // expect: true
+io.write(f != f) // expect: false

test/fn_syntax.wren

@@ -1,23 +1,25 @@
-// Single line.
-{ io.write("ok") }.call // expect: ok
+// Single expression body.
+(fn io.write("ok")).call // expect: ok
 
-// No trailing newline.
-{
-  io.write("ok") }.call // expect: ok
+// TODO(bob): Precedence of fn body.
 
-// Trailing newline.
-{
+// Curly body.
+fn {
   io.write("ok") // expect: ok
 }.call
 
+// No trailing newline.
+fn {
+  io.write("ok") }.call // expect: ok
+
 // Multiple expressions.
-{
+fn {
   io.write("1") // expect: 1
   io.write("2") // expect: 2
 }.call
 
 // Extra newlines.
-{
+fn {
 
 
   io.write("1") // expect: 1

test/undefined_local.wren

@@ -1,3 +1,3 @@
-{
+fn {
   io.write(notDefined)  // expect error
-}
+}.call