From 9fdfa1e32374f8d862c98ad241757853386f66e6 Mon Sep 17 00:00:00 2001
From: Antonio Maiorano <amaiorano@google.com>
Date: Mon, 10 May 2021 13:46:06 +0000
Subject: [PATCH] Resolver: validate else condition is boolean

Bug: tint:786
Change-Id: I5e4987e4eeb0608c640fc5c8ea035c8dca0ef187
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/50461
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
---
 src/resolver/resolver.cc        |  9 +++++++++
 src/resolver/resolver_test.cc   |  2 +-
 src/resolver/validation_test.cc | 14 ++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/resolver/resolver.cc b/src/resolver/resolver.cc
index 78f91fa701..658fca881a 100644
--- a/src/resolver/resolver.cc
+++ b/src/resolver/resolver.cc
@@ -1196,6 +1196,15 @@ bool Resolver::IfStatement(ast::IfStatement* stmt) {
       if (!Expression(cond)) {
         return false;
       }
+
+      auto* else_cond_type = TypeOf(cond)->UnwrapAll();
+      if (else_cond_type != builder_->ty.bool_()) {
+        diagnostics_.add_error(
+            "else statement condition must be bool, got " +
+                else_cond_type->FriendlyName(builder_->Symbols()),
+            cond->source());
+        return false;
+      }
     }
     Mark(else_stmt->body());
     if (!BlockStatement(else_stmt->body())) {
diff --git a/src/resolver/resolver_test.cc b/src/resolver/resolver_test.cc
index 88cfbb6d8a..1d6f22f87e 100644
--- a/src/resolver/resolver_test.cc
+++ b/src/resolver/resolver_test.cc
@@ -125,7 +125,7 @@ TEST_F(ResolverTest, Stmt_If) {
 
   auto* else_body = Block(Assign(else_lhs, else_rhs));
 
-  auto* else_cond = Expr(3);
+  auto* else_cond = Expr(true);
   auto* else_stmt = create<ast::ElseStatement>(else_cond, else_body);
 
   auto* lhs = Expr("v");
diff --git a/src/resolver/validation_test.cc b/src/resolver/validation_test.cc
index 4ffb66055f..6ad9df8ca0 100644
--- a/src/resolver/validation_test.cc
+++ b/src/resolver/validation_test.cc
@@ -147,6 +147,20 @@ TEST_F(ResolverValidationTest, Stmt_If_NonBool) {
             "12:34 error: if statement condition must be bool, got f32");
 }
 
+TEST_F(ResolverValidationTest, Stmt_Else_NonBool) {
+  // else (1.23f) {}
+
+  WrapInFunction(If(Expr(true), Block(),
+                    Else(create<ast::ScalarConstructorExpression>(
+                             Source{{12, 34}}, Literal(1.23f)),
+                         Block())));
+
+  EXPECT_FALSE(r()->Resolve());
+
+  EXPECT_EQ(r()->error(),
+            "12:34 error: else statement condition must be bool, got f32");
+}
+
 TEST_F(ResolverValidationTest,
        Stmt_VariableDecl_MismatchedTypeScalarConstructor) {
   u32 unsigned_value = 2u;  // Type does not match variable type