compiler: fix segmentation fault on compiling unexpected unary expressions

When compiling expressions followed by a unary operator, the compiler
triggered a segmentation fault due to invoking an unset infix parser
routine.

Explicitly handle this case and raise a syntax error if such an
invalid expression is encountered.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

2 files changed, 28 insertions, 0 deletions

diff --git a/compiler.c b/compiler.c
index d4725b1..e5a294a 100644
--- a/compiler.c
+++ b/compiler.c
@@ -372,6 +372,13 @@ uc_compiler_parse_precedence(uc_compiler_t *compiler, uc_precedence_t precedence
 
 		rule = uc_compiler_parse_rule(compiler->exprstack->token);
 
+		if (!rule->infix) {
+			uc_compiler_syntax_error(compiler, compiler->parser->curr.pos, "Expecting ';' or binary operator");
+			uc_compiler_parse_advance(compiler);
+
+			return;
+		}
+
 		/* allow reserved words in property accessors */
 		if (rule->infix == uc_compiler_compile_dot)
 			compiler->parser->lex.no_keyword = true;
diff --git a/tests/custom/04_bugs/37_compiler_unexpected_unary_op b/tests/custom/04_bugs/37_compiler_unexpected_unary_op
new file mode 100644
index 0000000..e652319
--- /dev/null
+++ b/tests/custom/04_bugs/37_compiler_unexpected_unary_op
@@ -0,0 +1,21 @@
+When compiling expressions followed by a unary operator, the compiler
+triggered a segmentation fault due to invoking an unset infix parser
+routine.
+
+-- Testcase --
+1~1
+-- End --
+
+-- Args --
+-R
+-- End --
+
+-- Expect stderr --
+Syntax error: Expecting ';' or binary operator
+In line 1, byte 2:
+
+ `1~1`
+   ^-- Near here
+
+
+-- End --