From fecf10664a7e955ed4d86a77c5c3445b580a9518 Mon Sep 17 00:00:00 2001
From: Ben Clayton <bclayton@google.com>
Date: Mon, 23 Nov 2020 20:07:15 +0000
Subject: [PATCH] Improve error message when suffixing float with f

Fixes: tint:277
Change-Id: I7ec3bb758c7d80c95c6ecd51eebf4144b696bec5
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/33668
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: David Neto <dneto@google.com>
---
 src/reader/wgsl/parser_impl.cc                | 5 +++++
 src/reader/wgsl/parser_impl_error_msg_test.cc | 7 +++++++
 2 files changed, 12 insertions(+)

diff --git a/src/reader/wgsl/parser_impl.cc b/src/reader/wgsl/parser_impl.cc
index f914bd4ee1..8e5c0cf672 100644
--- a/src/reader/wgsl/parser_impl.cc
+++ b/src/reader/wgsl/parser_impl.cc
@@ -2622,6 +2622,11 @@ Maybe<ast::Literal*> ParserImpl::const_literal() {
     return create<ast::UintLiteral>(type, t.to_u32());
   }
   if (match(Token::Type::kFloatLiteral)) {
+    auto p = peek();
+    if (p.IsIdentifier() && p.to_str() == "f") {
+      next();  // Consume 'f'
+      add_error(p.source(), "float literals must not be suffixed with 'f'");
+    }
     auto* type = module_.create<ast::type::F32Type>();
     return create<ast::FloatLiteral>(type, t.to_f32());
   }
diff --git a/src/reader/wgsl/parser_impl_error_msg_test.cc b/src/reader/wgsl/parser_impl_error_msg_test.cc
index cf5906bd31..8a533358b4 100644
--- a/src/reader/wgsl/parser_impl_error_msg_test.cc
+++ b/src/reader/wgsl/parser_impl_error_msg_test.cc
@@ -209,6 +209,13 @@ TEST_F(ParserImplErrorTest, EqualityInvalidExpr) {
          "                             ^\n");
 }
 
+TEST_F(ParserImplErrorTest, FloatLiteralSuffixedWithF) {
+  EXPECT("var f : f32 = 1.23f;",
+         "test.wgsl:1:19 error: float literals must not be suffixed with 'f'\n"
+         "var f : f32 = 1.23f;\n"
+         "                  ^\n");
+}
+
 TEST_F(ParserImplErrorTest, ForLoopInitializerMissingSemicolon) {
   EXPECT("fn f() -> void { for (var i : i32 = 0 i < 8; i=i+1) {} }",
          "test.wgsl:1:39 error: expected ';' for initializer in for loop\n"