From 9010c87a75e1b6198567c06b7243fd4cdcdf571c Mon Sep 17 00:00:00 2001
From: CooperSheroy <sheroycoops@gmail.com>
Date: Sat, 1 Aug 2026 09:12:05 +0530
Subject: [PATCH] fix: lower void conditionals as statements

---
 .../compiler/src/frontend/lowering/lower-calls.ts    | 10 ++--------
 .../compiler/src/frontend/lowering/lower-stmts.ts    | 12 ++++++++++++
 packages/compiler/src/frontend/lowering/lowerer.ts   | 11 +++++++++++
 tests/corpus/2352-void-coercions.ts                  |  7 +++++++
 4 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/packages/compiler/src/frontend/lowering/lower-calls.ts b/packages/compiler/src/frontend/lowering/lower-calls.ts
index 766fb2976..0c20157e7 100644
--- a/packages/compiler/src/frontend/lowering/lower-calls.ts
+++ b/packages/compiler/src/frontend/lowering/lower-calls.ts
@@ -5432,14 +5432,8 @@ const inliningPredicates = new Set<ts.Symbol>();
           // A `void e` body rides the statement lowering (the value is
           // discarded here, so the operand evaluates for effect alone —
           // `(name) => void doThing(name)`, the fire-and-forget arrow).
-          let stripped: ts.Expression = bodyExpr;
-          while (ts.isParenthesizedExpression(stripped)) stripped = stripped.expression;
-          if (ts.isVoidExpression(stripped)) {
-            body = [L.lowerExprStatement(stripped)];
-          } else {
-            const value = L.lowerExpr(bodyExpr);
-            body = value.kind === "unitLit" ? [] : [{ kind: "exprStmt", expr: value, loc: locOf(node.body!) }];
-          }
+          const stmt = L.lowerExprStatement(bodyExpr);
+          body = stmt.kind === "block" && stmt.body.length === 0 ? [] : [stmt];
         } else {
           let value = L.lowerExpr(bodyExpr);
           // An async concise body whose value is itself a promise
diff --git a/packages/compiler/src/frontend/lowering/lower-stmts.ts b/packages/compiler/src/frontend/lowering/lower-stmts.ts
index 9d08f5ea9..3766330db 100644
--- a/packages/compiler/src/frontend/lowering/lower-stmts.ts
+++ b/packages/compiler/src/frontend/lowering/lower-stmts.ts
@@ -4142,6 +4142,18 @@ function isEsModuleStamp(expr: ts.Expression): boolean {
     // Value-position `void` keeps the syntax fence (a standalone undefined
     // VALUE needs a union slot to live in).
     if (ts.isVoidExpression(expr)) return lowerExprStatement(L, expr.expression);
+    // Statement-position conditionals evaluate the condition, then exactly
+    // one arm for effect and drop that arm's value. Lower them as `if`
+    // statements so void-valued arms do not form invalid value ternaries.
+    if (ts.isConditionalExpression(expr)) {
+      return {
+        kind: "if",
+        cond: L.lowerCondition(expr.condition),
+        then: [lowerExprStatement(L, expr.whenTrue)],
+        else_: [lowerExprStatement(L, expr.whenFalse)],
+        loc: locOf(expr),
+      };
+    }
     if (ts.isBinaryExpression(expr)) {
       const opKind = expr.operatorToken.kind;
       // Statement-position comma (`({} = a, [] = a);`, `i++, j++` in a
diff --git a/packages/compiler/src/frontend/lowering/lowerer.ts b/packages/compiler/src/frontend/lowering/lowerer.ts
index fab1e4a93..112405546 100644
--- a/packages/compiler/src/frontend/lowering/lowerer.ts
+++ b/packages/compiler/src/frontend/lowering/lowerer.ts
@@ -5805,6 +5805,17 @@ export class Lowerer {
   lowerReturnStmt(node: ts.Expression, loc: SrcLoc): IrStmt {
     const expected = this.ctx.returnType;
     if (expected.kind === "void") {
+      let expr = node;
+      while (ts.isParenthesizedExpression(expr)) expr = expr.expression;
+      if (ts.isConditionalExpression(expr)) {
+        return {
+          kind: "if",
+          cond: this.lowerCondition(expr.condition),
+          then: [this.lowerReturnStmt(expr.whenTrue, loc)],
+          else_: [this.lowerReturnStmt(expr.whenFalse, loc)],
+          loc,
+        };
+      }
       let e = this.lowerExpr(node);
       if (this.ctx.isAsync && e.type.kind === "promise") {
         e = { kind: "awaitExpr", value: e, type: e.type.inner, loc: e.loc };
diff --git a/tests/corpus/2352-void-coercions.ts b/tests/corpus/2352-void-coercions.ts
index 2f333667f..47d296a10 100644
--- a/tests/corpus/2352-void-coercions.ts
+++ b/tests/corpus/2352-void-coercions.ts
@@ -46,6 +46,13 @@ const box = {
 box.poke();
 console.log("method unit return ok");
 
+// Concise void-returning arrows over conditional void calls lower as a
+// branch, not a value ternary.
+const branchVoid = (flag: boolean) => (flag ? box.poke() : fv());
+branchVoid(true);
+branchVoid(false);
+console.log("branch-void", effects);
+
 // Async concise body over an existing promise: resolves through.
 async function inner(): Promise<number> {
   return 42;