internal/shader: bug fix: forbid to have an initial value for uniform variables

Closes #2711

internal/shader/shader.go

@@ -395,6 +395,11 @@ func (cs *compileState) parseDecl(b *block, fname string, d ast.Decl) ([]shaderi
 
 				stmts = append(stmts, ss...)
 				if b == &cs.global {
+					if len(inits) > 0 {
+						cs.addError(s.Pos(), "a uniform variable cannot have initial values")
+						return nil, false
+					}
+
 					// TODO: Should rhs be ignored?
 					for i, v := range vs {
 						if !strings.HasPrefix(v.name, "__") {

internal/shader/syntax_test.go

@@ -3260,6 +3260,20 @@ func foo(x vec2) {
 }`)); err == nil {
 		t.Error("compileToIR must return an error but did not")
 	}
+
+	// Issue #2711
+	if _, err := compileToIR([]byte(`package main
+
+var Foo float = 1
+`)); err == nil {
+		t.Error("compileToIR must return an error but did not")
+	}
+	if _, err := compileToIR([]byte(`package main
+
+var Foo, Bar int = 1, 1
+`)); err == nil {
+		t.Error("compileToIR must return an error but did not")
+	}
 }
 
 // Issue #2705