From 6c9f93b7de42136c5c09f195fc1c4999e5962347 Mon Sep 17 00:00:00 2001
From: Erich Gubler <erichdongubler@gmail.com>
Date: Fri, 13 Dec 2024 11:15:51 -0500
Subject: [PATCH] diag(naga): clarify `select` built-in type mismatch messages

---
 naga/src/valid/expression.rs | 24 +++++++++++++++++++-----
 naga/tests/validation.rs     |  4 ++--
 naga/tests/wgsl_errors.rs    |  2 +-
 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/naga/src/valid/expression.rs b/naga/src/valid/expression.rs
index 28b9321cce..5f3c0a819c 100644
--- a/naga/src/valid/expression.rs
+++ b/naga/src/valid/expression.rs
@@ -54,8 +54,13 @@ pub enum ExpressionError {
         rhs_expr: Handle<crate::Expression>,
         rhs_type: crate::TypeInner,
     },
-    #[error("Selecting is not possible")]
-    InvalidSelectTypes,
+    #[error("Expected selection argument types to match, but reject value of type {reject:?} does not match accept value of value {accept:?}")]
+    SelectValuesTypeMismatch {
+        accept: crate::TypeInner,
+        reject: crate::TypeInner,
+    },
+    #[error("Expected selection condition to be a boolean value, got {actual:?}")]
+    SelectConditionNotABool { actual: crate::TypeInner },
     #[error("Relational argument {0:?} is not a boolean vector")]
     InvalidBooleanVector(Handle<crate::Expression>),
     #[error("Relational argument {0:?} is not a float")]
@@ -901,7 +906,8 @@ impl super::Validator {
             } => {
                 let accept_inner = &resolver[accept];
                 let reject_inner = &resolver[reject];
-                let condition_good = match resolver[condition] {
+                let condition_ty = &resolver[condition];
+                let condition_good = match *condition_ty {
                     Ti::Scalar(Sc {
                         kind: Sk::Bool,
                         width: _,
@@ -928,8 +934,16 @@ impl super::Validator {
                     },
                     _ => false,
                 };
-                if !condition_good || accept_inner != reject_inner {
-                    return Err(ExpressionError::InvalidSelectTypes);
+                if accept_inner != reject_inner {
+                    return Err(ExpressionError::SelectValuesTypeMismatch {
+                        accept: accept_inner.clone(),
+                        reject: reject_inner.clone(),
+                    });
+                }
+                if !condition_good {
+                    return Err(ExpressionError::SelectConditionNotABool {
+                        actual: condition_ty.clone(),
+                    });
                 }
                 ShaderStages::all()
             }
diff --git a/naga/tests/validation.rs b/naga/tests/validation.rs
index cd56355d1e..3ffb231e25 100644
--- a/naga/tests/validation.rs
+++ b/naga/tests/validation.rs
@@ -650,7 +650,7 @@ error: Entry point main at Compute is invalid
   │         ^^^^^^ naga::Expression [3]
   │
   = Expression [3] is invalid
-  = Selecting is not possible
+  = Expected selection condition to be a boolean value, got Scalar(Scalar { kind: Sint, width: 4 })
 
 ",
         ),
@@ -670,7 +670,7 @@ error: Entry point main at Compute is invalid
   │         ^^^^^^ naga::Expression [3]
   │
   = Expression [3] is invalid
-  = Selecting is not possible
+  = Expected selection argument types to match, but reject value of type Scalar(Scalar { kind: Bool, width: 1 }) does not match accept value of value Scalar(Scalar { kind: Sint, width: 4 })
 
 ",
         ),
diff --git a/naga/tests/wgsl_errors.rs b/naga/tests/wgsl_errors.rs
index acc2f32cbf..2d1669ada2 100644
--- a/naga/tests/wgsl_errors.rs
+++ b/naga/tests/wgsl_errors.rs
@@ -1543,7 +1543,7 @@ fn select() {
             naga::valid::ValidationError::Function {
                 name,
                 source: naga::valid::FunctionError::Expression {
-                    source: naga::valid::ExpressionError::InvalidSelectTypes,
+                    source: naga::valid::ExpressionError::SelectConditionNotABool { .. },
                     ..
                 },
                 ..