[fine] Tests for conditional, semicolon optional at end of block

Just like rust, ';' means "discard this value".

fine/src/parser/concrete.rs

@@ -422,7 +422,9 @@ fn statement_let(p: &mut CParser) {
     p.expect(TokenKind::Identifier, "expected a name for the variable");
     p.expect(TokenKind::Equal, "expected a '=' after the variable name");
     expression(p);
-    p.expect(TokenKind::Semicolon, "expect ';' to end a let statement");
+    if !p.at(TokenKind::RightBrace) {
+        p.expect(TokenKind::Semicolon, "expect ';' to end a let statement");
+    }
 
     p.end(m, TreeKind::LetStatement);
 }
@@ -436,7 +438,9 @@ fn statement_return(p: &mut CParser) {
         "expect 'return' to start a return statement",
     );
     expression(p);
-    p.expect(TokenKind::Semicolon, "expect ';' to end a return statement");
+    if !p.at(TokenKind::RightBrace) {
+        p.expect(TokenKind::Semicolon, "expect ';' to end a return statement");
+    }
 
     p.end(m, TreeKind::ReturnStatement);
 }
@@ -445,10 +449,12 @@ fn statement_expression(p: &mut CParser) {
     let m = p.start();
 
     expression(p);
-    p.expect(
-        TokenKind::Semicolon,
-        "expect ';' to end an expression statement",
-    );
+    if !p.at(TokenKind::RightBrace) {
+        p.expect(
+            TokenKind::Semicolon,
+            "expect ';' to end an expression statement",
+        );
+    }
 
     p.end(m, TreeKind::ExpressionStatement);
 }

fine/tests/expression/conditional.fine

@@ -0,0 +1,26 @@
+// concrete:
+// | File
+// |   IfStatement
+// |     ConditionalExpression
+// |       If:'"if"'
+// |       LiteralExpression
+// |         True:'"true"'
+// |       Block
+// |         LeftBrace:'"{"'
+// |         ExpressionStatement
+// |           LiteralExpression
+// |             String:'"\"discarded\""'
+// |           Semicolon:'";"'
+// |         ExpressionStatement
+// |           LiteralExpression
+// |             Number:'"23"'
+// |         RightBrace:'"}"'
+// |       Else:'"else"'
+// |       Block
+// |         LeftBrace:'"{"'
+// |         ExpressionStatement
+// |           LiteralExpression
+// |             Number:'"45"'
+// |         RightBrace:'"}"'
+//
+if true { "discarded"; 23 } else { 45 }