From ab2cf8b84244470e31fcee76efaa04c16015e4b7 Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <kvarkus@gmail.com>
Date: Tue, 26 Jan 2021 23:29:40 -0500
Subject: [PATCH] [wgsl] support vector type casts

---
 src/front/wgsl/mod.rs                      | 35 ++++++++++++----------
 src/front/wgsl/tests.rs                    |  9 ++++++
 tests/snapshots/snapshots__skybox.msl.snap |  4 +--
 3 files changed, 30 insertions(+), 18 deletions(-)

diff --git a/src/front/wgsl/mod.rs b/src/front/wgsl/mod.rs
index 6f647e6f76..bd2412bf42 100644
--- a/src/front/wgsl/mod.rs
+++ b/src/front/wgsl/mod.rs
@@ -62,6 +62,8 @@ pub enum Error<'a> {
     BadTexture(&'a str),
     #[error("bad texture coordinate")]
     BadCoordinate,
+    #[error("invalid type cast to `{0}`")]
+    BadTypeCast(&'a str),
     #[error(transparent)]
     InvalidResolve(ResolveError),
     #[error("unknown import: `{0}`")]
@@ -435,15 +437,6 @@ impl Parser {
             let expr = self.parse_general_expression(lexer, ctx.reborrow())?;
             lexer.expect(Token::Paren(')'))?;
             Some(crate::Expression::Derivative { axis, expr })
-        } else if let Some((kind, _width)) = conv::get_scalar_type(name) {
-            lexer.expect(Token::Paren('('))?;
-            let expr = self.parse_general_expression(lexer, ctx.reborrow())?;
-            lexer.expect(Token::Paren(')'))?;
-            Some(crate::Expression::As {
-                expr,
-                kind,
-                convert: true,
-            })
         } else if let Some(fun) = conv::map_standard_fun(name) {
             lexer.expect(Token::Paren('('))?;
             let arg_count = fun.argument_count();
@@ -833,18 +826,28 @@ impl Parser {
                         ctx.types,
                         ctx.constants,
                     )?;
+                    let kind = inner.scalar_kind();
                     let ty = ctx.types.fetch_or_append(crate::Type { name: None, inner });
 
                     lexer.expect(Token::Paren('('))?;
                     let mut components = Vec::new();
-                    while !lexer.skip(Token::Paren(')')) {
-                        if !components.is_empty() {
-                            lexer.expect(Token::Separator(','))?;
-                        }
-                        let sub_expr = self.parse_general_expression(lexer, ctx.reborrow())?;
-                        components.push(sub_expr);
+                    let mut last_component =
+                        self.parse_general_expression(lexer, ctx.reborrow())?;
+                    while lexer.skip(Token::Separator(',')) {
+                        components.push(last_component);
+                        last_component = self.parse_general_expression(lexer, ctx.reborrow())?;
+                    }
+                    lexer.expect(Token::Paren(')'))?;
+                    if components.is_empty() {
+                        crate::Expression::As {
+                            expr: last_component,
+                            kind: kind.ok_or(Error::BadTypeCast(word))?,
+                            convert: true,
+                        }
+                    } else {
+                        components.push(last_component);
+                        crate::Expression::Compose { ty, components }
                     }
-                    crate::Expression::Compose { ty, components }
                 }
             }
             other => return other.unexpected("primary expression"),
diff --git a/src/front/wgsl/tests.rs b/src/front/wgsl/tests.rs
index 6ef5e0460b..01dfc57c8c 100644
--- a/src/front/wgsl/tests.rs
+++ b/src/front/wgsl/tests.rs
@@ -37,6 +37,15 @@ fn parse_type_cast() {
     ",
     )
     .unwrap();
+    parse_str(
+        "
+        fn main() {
+            const x: vec2<f32> = vec2<f32>(1.0, 2.0);
+            const y: vec2<u32> = vec2<u32>(x);
+        }
+    ",
+    )
+    .unwrap();
 }
 
 #[test]
diff --git a/tests/snapshots/snapshots__skybox.msl.snap b/tests/snapshots/snapshots__skybox.msl.snap
index ce8662f0d5..ed0e4a72d8 100644
--- a/tests/snapshots/snapshots__skybox.msl.snap
+++ b/tests/snapshots/snapshots__skybox.msl.snap
@@ -20,9 +20,9 @@ struct Data {
 
 typedef int type4;
 
-typedef metal::float3x3 type5;
+typedef float type5;
 
-typedef float type6;
+typedef metal::float3x3 type6;
 
 typedef metal::texturecube<float, metal::access::sample> type7;