tint: Add Symbol inequality operator

Allows Symbol to be used in a std::variant

Change-Id: If366622c39b5c25d633f6507467c9859394577c3
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/112283
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Ben Clayton <bclayton@google.com>

src/tint/symbol.cc

@@ -42,6 +42,11 @@ bool Symbol::operator==(const Symbol& other) const {
     return val_ == other.val_;
 }
 
+bool Symbol::operator!=(const Symbol& other) const {
+    TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID(Symbol, program_id_, other.program_id_);
+    return val_ != other.val_;
+}
+
 bool Symbol::operator<(const Symbol& other) const {
     TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID(Symbol, program_id_, other.program_id_);
     return val_ < other.val_;

src/tint/symbol.h

@@ -63,11 +63,16 @@ class Symbol {
     /// @returns teh symbol after doing the move
     Symbol& operator=(Symbol&& o);
 
-    /// Comparison operator
+    /// Equality operator
     /// @param o the other symbol
     /// @returns true if the symbols are the same
     bool operator==(const Symbol& o) const;
 
+    /// Inequality operator
+    /// @param o the other symbol
+    /// @returns true if the symbols are the different
+    bool operator!=(const Symbol& o) const;
+
     /// Less-than operator
     /// @param o the other symbol
     /// @returns true if this symbol is ordered before symbol `o`

src/tint/symbol_test.cc

@@ -43,8 +43,11 @@ TEST_F(SymbolTest, Comparison) {
     Symbol sym3(1, program_id);
 
     EXPECT_TRUE(sym1 == sym3);
+    EXPECT_FALSE(sym1 != sym3);
     EXPECT_FALSE(sym1 == sym2);
+    EXPECT_TRUE(sym1 != sym2);
     EXPECT_FALSE(sym3 == sym2);
+    EXPECT_TRUE(sym3 != sym2);
 }
 
 }  // namespace