tests: add tests for error propagation

Except for the `TupleCons` one, the added tests represent code that was
previously failing.

Author: zerbina

tests/errors/README.md

@@ -0,0 +1,3 @@
+This directory contains tests for error handling. More specifically, tests that
+make sure the compiler is able continue without crashing after encountering an
+error in the input program.

tests/errors/terror_in_call_argument.test

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+discard """
+  description: "Either the if or else branch has an error"
+  reject: true
+"""
+(Module
+  (ProcDecl (Ident "test") (UnitTy) (Params (ParamDecl (Ident "x") (IntTy)))
+    (Return))
+  (ProcDecl (Ident "main") (UnitTy) (Params)
+    (Call (Ident "test") (Ident "missing"))))

tests/errors/terror_in_if.test

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+discard """
+  description: "Either the if or else branch has an error"
+  reject: true
+"""
+(If (Ident "true")
+  (Ident "missing")
+  (IntVal 10))

tests/errors/terror_in_tuple_cons.test

@@ -0,0 +1,5 @@
+discard """
+  description: "Either the if or else branch has an error"
+  reject: true
+"""
+(TupleCons (Ident "missing"))