Fix assignment operator precedence

Author: msujew

src/interpreter/runner.ts

@@ -185,17 +185,23 @@ async function runExpression(expression: Expression, context: RunnerContext): Pr
     } else if (isUnaryExpression(expression)) {
         const { operator, value } = expression;
         const actualValue = await runExpression(value, context);
-        if (operator === '-') {
+        if (operator === '+') {
+            if (typeof actualValue === 'number') {
+                return actualValue;
+            } else {
+                throw new AstNodeError(expression, `Cannot apply operator '${operator}' to value of type '${typeof actualValue}'`);
+            }
+        } else if (operator === '-') {
             if (typeof actualValue === 'number') {
                 return -actualValue;
             } else {
-                throw new AstNodeError(expression, `Cannot apply operator '${operator}' to values of type '${typeof actualValue}'`);
+                throw new AstNodeError(expression, `Cannot apply operator '${operator}' to value of type '${typeof actualValue}'`);
             }
         } else if (operator === '!') {
             if (typeof actualValue === 'boolean') {
                 return !actualValue;
             } else {
-                throw new AstNodeError(expression, `Cannot apply operator '${operator}' to values of type '${typeof actualValue}'`);
+                throw new AstNodeError(expression, `Cannot apply operator '${operator}' to value of type '${typeof actualValue}'`);
             }
         }
     } else if (isNumberExpression(expression)) {

src/language-server/lox.langium

@@ -42,7 +42,10 @@ VariableDeclaration returns NamedElement:
 ;
 
 Expression:
-    Addition;
+    Assignment;
+
+Assignment infers Expression:
+    Addition ({infer BinaryExpression.left=current} operator=('=') right=Addition)*;
 
 Addition infers Expression:
     Multiplication ({infer BinaryExpression.left=current} operator=('+' | '-') right=Multiplication)*;
@@ -54,10 +57,7 @@ Logical infers Expression:
     Comparison ({infer BinaryExpression.left=current} operator=('and' | 'or') right=Comparison)*;
 
 Comparison infers Expression:
-    Assignment ({infer BinaryExpression.left=current} operator=('<' | '<=' | '>' | '>=' | '==' | '!=') right=Assignment)*;
-
-Assignment infers Expression:
-    MemberCall ({infer BinaryExpression.left=current} operator=('=') right=MemberCall)*;
+    MemberCall ({infer BinaryExpression.left=current} operator=('<' | '<=' | '>' | '>=' | '==' | '!=') right=MemberCall)*;
 
 MemberCall infers Expression:
     Primary