fix: Prevent division by zero when folding constants

Author: giann

src/Ast.zig

@@ -683,6 +683,17 @@ pub const Slice = struct {
                 return Value.fromInteger(right_integer.? *% left_integer.?);
             },
             .Slash => {
+                if (right_float == 0 or right_integer == 0) {
+                    reporter.reportErrorAt(
+                        .runtime,
+                        self.tokens.get(self.nodes.items(.location)[components.right]),
+                        self.tokens.get(self.nodes.items(.end_location)[components.right]),
+                        "Division by zero.",
+                    );
+
+                    return error.DivisionByZero;
+                }
+
                 if (right_float) |rf| {
                     return Value.fromDouble(left_float.? / rf);
                 }

src/Codegen.zig

@@ -23,6 +23,7 @@ const Self = @This();
 pub const Error = error{
     CantCompile,
     UnwrappedNull,
+    DivisionByZero,
     OutOfBound,
     ReachedMaximumMemoryUsage,
     WriteFailed,
@@ -439,14 +440,12 @@ fn generateNode(self: *Self, node: Ast.Node.Index, breaks: ?*Breaks) Error!?*obj
 fn nodeValue(self: *Self, node: Ast.Node.Index) Error!?Value {
     const value = &self.ast.nodes.items(.value)[node];
 
-    if (value.* == null) {
-        if (self.ast.isConstant(node)) {
-            value.* = try self.ast.typeCheckAndToValue(
-                node,
-                &self.reporter,
-                self.gc,
-            );
-        }
+    if (value.* == null and self.ast.isConstant(node)) {
+        value.* = try self.ast.typeCheckAndToValue(
+            node,
+            &self.reporter,
+            self.gc,
+        );
     }
 
     return value.*;

src/Jit.zig

@@ -19,6 +19,7 @@ pub const Error = error{
     CantCompile,
     UnwrappedNull,
     OutOfBound,
+    DivisionByZero,
     ReachedMaximumMemoryUsage,
     WriteFailed,
 } || std.mem.Allocator.Error || std.fmt.BufPrintError;
@@ -2731,7 +2732,7 @@ fn buildBinary(
                 },
                 else => unreachable,
             }
-       },
+        },
         .Star, .StarEqual => {
             switch (def_type) {
                 .Integer => {
@@ -2746,12 +2747,44 @@ fn buildBinary(
             }
         },
         .Slash, .SlashEqual => {
+            const zero_label = m.MIR_new_label(self.ctx);
+
             switch (def_type) {
                 .Integer => {
+                    self.BNE(
+                        zero_label,
+                        right,
+                        m.MIR_new_uint_op(self.ctx, Value.fromInteger(0)),
+                    );
+
+                    // Exit if division by zero
+                    // FIXME: would be great to be able to report cleanly the error but how to have string constant in MIR?
+                    try self.buildExternApiCall(
+                        .exit,
+                        null,
+                        &[_]m.MIR_op_t{m.MIR_new_uint_op(self.ctx, 1)},
+                    );
+
+                    self.append(zero_label);
                     self.DIV(dest, left, right);
                     try self.wrap(.Integer, dest, dest);
                 },
                 .Double => {
+                    self.BNE(
+                        zero_label,
+                        right,
+                        m.MIR_new_uint_op(self.ctx, Value.fromDouble(0)),
+                    );
+
+                    // Exit if division by zero
+                    // FIXME: would be great to be able to report cleanly the error but how to have string constant in MIR?
+                    try self.buildExternApiCall(
+                        .exit,
+                        null,
+                        &[_]m.MIR_op_t{m.MIR_new_uint_op(self.ctx, 1)},
+                    );
+
+                    self.append(zero_label);
                     self.DDIV(left, left, right);
                     try self.wrap(.Double, left, dest);
                 },

src/Parser.zig

@@ -444,6 +444,7 @@ pub const Error = error{
     ImportError,
     CantCompile,
     UnwrappedNull,
+    DivisionByZero,
     OutOfBound,
     ReachedMaximumMemoryUsage,
     WriteFailed,
@@ -4887,7 +4888,7 @@ fn dot(self: *Self, can_assign: bool, callee: Ast.Node.Index) Error!Ast.Node.Ind
         .{
             .tag = .Dot,
             .location = start_location,
-            .end_location = undefined,
+            .end_location = start_location,
             .components = .{
                 .Dot = .{
                     .callee = callee,

src/vm.zig

@@ -428,6 +428,7 @@ pub const VM = struct {
         UnwrappedNull,
         OutOfBound,
         NumberOverflow,
+        DivisionByZero,
         NotInFiber,
         FiberOver,
         BadNumber,
@@ -1532,7 +1533,9 @@ pub const VM = struct {
             catch_value,
         ) catch |err| {
             switch (err) {
-                Error.RuntimeError => return,
+                Error.RuntimeError,
+                Error.DivisionByZero,
+                => return,
                 else => {
                     self.panic("Out of memory");
                     unreachable;
@@ -4800,7 +4803,7 @@ pub const VM = struct {
         }
     }
 
-    fn reportRuntimeErrorWithCurrentStack(self: *Self, message: []const u8) void {
+    pub fn reportRuntimeErrorWithCurrentStack(self: *Self, message: []const u8) void {
         self.reportRuntimeError(
             message,
             if (self.currentFrame()) |frame|