From 74c4a3ce184d9bc378a03b48affc8c3fa074105a Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <kvarkus@gmail.com>
Date: Wed, 16 Sep 2020 00:48:37 -0400
Subject: [PATCH] Add ArrayLength expression

---
 src/back/glsl.rs      | 4 ++++
 src/lib.rs            | 2 ++
 src/proc/interface.rs | 3 +++
 src/proc/typifier.rs  | 4 ++++
 4 files changed, 13 insertions(+)

diff --git a/src/back/glsl.rs b/src/back/glsl.rs
index c3003dccaf..cbb8fd26ac 100644
--- a/src/back/glsl.rs
+++ b/src/back/glsl.rs
@@ -1042,6 +1042,10 @@ fn write_expression<'a, 'b>(
                     .join(","),
             ))
         }
+        Expression::ArrayLength(expr) => {
+            let base = write_expression(&builder.expressions[expr], module, builder)?;
+            Cow::Owned(format!("uint({}.length())", base))
+        }
     })
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index 2b65d8ac81..4cded46cac 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -635,6 +635,8 @@ pub enum Expression {
         origin: FunctionOrigin,
         arguments: Vec<Handle<Expression>>,
     },
+    /// Get dynamic array length.
+    ArrayLength(Handle<Expression>),
 }
 
 /// A code block is just a vector of statements.
diff --git a/src/proc/interface.rs b/src/proc/interface.rs
index ff4290c192..8e1f5666ce 100644
--- a/src/proc/interface.rs
+++ b/src/proc/interface.rs
@@ -100,6 +100,9 @@ where
                     self.traverse_expr(argument);
                 }
             }
+            E::ArrayLength(expr) => {
+                self.traverse_expr(expr);
+            }
         }
     }
 
diff --git a/src/proc/typifier.rs b/src/proc/typifier.rs
index 787c8adacf..461bfa1bbd 100644
--- a/src/proc/typifier.rs
+++ b/src/proc/typifier.rs
@@ -262,6 +262,10 @@ impl Typifier {
                     .ok_or(ResolveError::FunctionReturnsVoid)?;
                 Resolution::Handle(ty)
             }
+            crate::Expression::ArrayLength(_) => Resolution::Value(crate::TypeInner::Scalar {
+                kind: crate::ScalarKind::Uint,
+                width: 4,
+            }),
         })
     }