internal/shader: bug fix: unexpected crash for out of range

Closes #2926

internal/shader/expr.go

@@ -73,6 +73,10 @@ func (cs *compileState) parseExpr(block *block, fname string, expr ast.Expr, mar
 			return nil, nil, nil, false
 		}
 		stmts = append(stmts, ss...)
+		if len(ts) == 0 {
+			cs.addError(e.Pos(), fmt.Sprintf("unexpected binary operator: %s", e.X))
+			return nil, nil, nil, false
+		}
 		lhst := ts[0]
 
 		rhs, ts, ss, ok := cs.parseExpr(block, fname, e.Y, markLocalVariableUsed)
@@ -921,7 +925,7 @@ func (cs *compileState) parseExpr(block *block, fname string, expr ast.Expr, mar
 			return nil, nil, nil, false
 		}
 
-		if !isValidSwizzling(e.Sel.Name, types[0]) {
+		if len(types) == 0 || !isValidSwizzling(e.Sel.Name, types[0]) {
 			cs.addError(e.Pos(), fmt.Sprintf("unexpected swizzling: %s", e.Sel.Name))
 			return nil, nil, nil, false
 		}
@@ -977,6 +981,10 @@ func (cs *compileState) parseExpr(block *block, fname string, expr ast.Expr, mar
 			cs.addError(e.Pos(), fmt.Sprintf("multiple-value context is not available at a unary operator: %s", e.X))
 			return nil, nil, nil, false
 		}
+		if len(ts) == 0 {
+			cs.addError(e.Pos(), fmt.Sprintf("unexpected unary operator: %s", e.X))
+			return nil, nil, nil, false
+		}
 
 		if exprs[0].Const != nil {
 			v := gconstant.UnaryOp(e.Op, exprs[0].Const, 0)
@@ -1124,6 +1132,10 @@ func (cs *compileState) parseExpr(block *block, fname string, expr ast.Expr, mar
 			cs.addError(e.Pos(), "multiple-value context is not available at an index expression")
 			return nil, nil, nil, false
 		}
+		if len(ts) == 0 {
+			cs.addError(e.Pos(), "unexpected index expression")
+			return nil, nil, nil, false
+		}
 		x := exprs[0]
 		t := ts[0]
 

internal/shader/syntax_test.go

@@ -4061,3 +4061,51 @@ func Bar() (int, int) {
 		t.Error("compileToIR must return an error but did not")
 	}
 }
+
+// Issue #2926
+func TestSyntaxNonTypeExpression(t *testing.T) {
+	if _, err := compileToIR([]byte(`package main
+
+func Foo() {
+}
+
+func Bar() float {
+	return +Foo
+}
+`)); err == nil {
+		t.Error("compileToIR must return an error but did not")
+	}
+	if _, err := compileToIR([]byte(`package main
+
+func Foo() {
+}
+
+func Bar() float {
+	return Foo + 1.0
+}
+`)); err == nil {
+		t.Error("compileToIR must return an error but did not")
+	}
+	if _, err := compileToIR([]byte(`package main
+
+func Foo() {
+}
+
+func Bar() float {
+	return Foo.x
+}
+`)); err == nil {
+		t.Error("compileToIR must return an error but did not")
+	}
+	if _, err := compileToIR([]byte(`package main
+
+func Foo() {
+}
+
+func Bar() float {
+	return Foo[0]
+}
+`)); err == nil {
+		t.Error("compileToIR must return an error but did not")
+	}
+}