Add if expression support to the compiler

Author: toxamin

src/prometheus/compiler/compiler.lua

@@ -2359,6 +2359,64 @@ function Compiler:compileExpression(expression, funcDepth, numReturns)
         return regs;
     end
 
+    if(expression.kind == AstKind.IfElseExpression) then
+        local posState = self.registers[self.POS_REGISTER];
+        self.registers[self.POS_REGISTER] = self.VAR_REGISTER;
+
+        local regs = {};
+        for i=1, numReturns do
+            regs[i] = self:allocRegister();
+            if(i ~= 1) then
+                self:addStatement(self:setRegister(scope, regs[i], Ast.NilExpression()), {regs[i]}, {}, false);
+            end
+        end
+
+        local resReg = regs[1];
+        local tmpReg;
+
+        if posState then
+            tmpReg = self:allocRegister(false);
+            self:addStatement(self:copyRegisters(scope, {tmpReg}, {self.POS_REGISTER}), {tmpReg}, {self.POS_REGISTER}, false);
+        end
+
+        local conditionReg = self:compileExpression(expression.condition, funcDepth, 1)[1];
+
+        local trueBlock, falseBlock, finalBlock = self:createBlock(), self:createBlock(), self:createBlock();
+
+        self:addStatement(self:setRegister(scope, self.POS_REGISTER, Ast.OrExpression(Ast.AndExpression(self:register(scope, conditionReg), Ast.NumberExpression(trueBlock.id)), Ast.NumberExpression(falseBlock.id))), {self.POS_REGISTER}, {conditionReg}, false);
+        self:freeRegister(conditionReg, false);
+
+        do
+            self:setActiveBlock(trueBlock);
+            local scope = trueBlock.scope;
+            local trueReg = self:compileExpression(expression.true_value, funcDepth, 1)[1];
+            self:addStatement(self:copyRegisters(scope, {resReg}, {trueReg}), {resReg}, {trueReg}, false);
+            self:freeRegister(trueReg, false);
+            self:addStatement(self:setRegister(scope, self.POS_REGISTER, Ast.NumberExpression(finalBlock.id)), {self.POS_REGISTER}, {}, false);
+        end
+
+        do
+            self:setActiveBlock(falseBlock);
+            local scope = falseBlock.scope;
+            local falseReg = self:compileExpression(expression.false_value, funcDepth, 1)[1];
+            self:addStatement(self:copyRegisters(scope, {resReg}, {falseReg}), {resReg}, {falseReg}, false);
+            self:freeRegister(falseReg, false);
+            self:addStatement(self:setRegister(scope, self.POS_REGISTER, Ast.NumberExpression(finalBlock.id)), {self.POS_REGISTER}, {}, false);
+        end
+
+        self.registers[self.POS_REGISTER] = posState;
+
+        self:setActiveBlock(finalBlock);
+        scope = finalBlock.scope;
+
+        if tmpReg then
+            self:addStatement(self:copyRegisters(scope, {self.POS_REGISTER}, {tmpReg}), {self.POS_REGISTER}, {tmpReg}, false);
+            self:freeRegister(tmpReg, false);
+        end
+
+        return regs;
+    end
+
     logger:error(string.format("%s is not an compliable expression!", expression.kind));
 end
 

src/prometheus/visitast.lua

@@ -237,8 +237,8 @@ function visitExpression(expression, previsit, postvisit, data)
 	end
 	if(expression.kind == AstKind.IfElseExpression) then
 		expression.condition = visitExpression(expression.condition, previsit, postvisit, data);
-		expression.true_expr = visitExpression(expression.true_expr, previsit, postvisit, data);
-		expression.false_expr = visitExpression(expression.false_expr, previsit, postvisit, data);
+		expression.true_value = visitExpression(expression.true_value, previsit, postvisit, data);
+		expression.false_value = visitExpression(expression.false_value, previsit, postvisit, data);
 	end
 
 	if(type(postvisit) == "function") then