tcl: Phase 4 error handling — catch/try/throw/return-code (+39 tests, 267 total)

Implements catch, throw, try, return -code options, and error with
errorinfo/errorcode fields. catch runs sub-script isolated, captures
result and exit code (0-4); try dispatches on/finally clauses;
throw sets code 1 with errorcode; return -code parses flag options.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/tcl/tests/error.sx

@@ -0,0 +1,192 @@
+; Tcl-on-SX error handling tests (Phase 4)
+(define tcl-err-pass 0)
+(define tcl-err-fail 0)
+(define tcl-err-failures (list))
+
+(define
+  tcl-err-assert
+  (fn
+    (label expected actual)
+    (if
+      (equal? expected actual)
+      (set! tcl-err-pass (+ tcl-err-pass 1))
+      (begin
+        (set! tcl-err-fail (+ tcl-err-fail 1))
+        (append!
+          tcl-err-failures
+          (str label ": expected=" (str expected) " got=" (str actual)))))))
+
+(define
+  tcl-run-error-tests
+  (fn
+    ()
+    (set! tcl-err-pass 0)
+    (set! tcl-err-fail 0)
+    (set! tcl-err-failures (list))
+    (define interp (fn () (make-default-tcl-interp)))
+    (define run (fn (src) (tcl-eval-string (interp) src)))
+    (define
+      ok
+      (fn (label actual expected) (tcl-err-assert label expected actual)))
+    (define
+      ok?
+      (fn (label condition) (tcl-err-assert label true condition)))
+
+    ; --- catch basic ---
+    (ok "catch-ok-code" (get (run "catch {set x 1}") :result) "0")
+    (ok "catch-ok-result-var" (tcl-var-get (run "catch {set x hello} r") "r") "hello")
+    (ok "catch-ok-returns-0" (get (run "catch {set x hello} r") :result) "0")
+
+    ; --- catch error ---
+    (ok "catch-error-code" (get (run "catch {error oops} r") :result) "1")
+    (ok "catch-error-result-var" (tcl-var-get (run "catch {error oops} r") "r") "oops")
+
+    ; --- catch outer code stays 0 ---
+    (ok? "catch-outer-code-ok" (= (get (run "catch {error boom} r") :code) 0))
+
+    ; --- catch code 2 (return) ---
+    (ok "catch-return-code" (get (run "proc p {} {return hello}\ncatch {p} r") :result) "0")
+    (ok "catch-return-val" (tcl-var-get (run "proc p {} {return hello}\ncatch {p} r") "r") "hello")
+
+    ; --- catch code 3 (break) ---
+    (ok "catch-break-code" (get (run "catch {break} r") :result) "3")
+
+    ; --- catch code 4 (continue) ---
+    (ok "catch-continue-code" (get (run "catch {continue} r") :result) "4")
+
+    ; --- catch no resultVar ---
+    (ok "catch-no-var-ok" (get (run "catch {set x 1}") :result) "0")
+    (ok "catch-no-var-err" (get (run "catch {error boom}") :result) "1")
+
+    ; --- catch with optsVar ---
+    (ok? "catch-opts-var-set"
+      (let
+        ((i (run "catch {error boom} r opts")))
+        (not (equal? (tcl-var-get i "opts") ""))))
+    (ok? "catch-opts-contains-code"
+      (let
+        ((i (run "catch {error boom} r opts")))
+        (let
+          ((opts-str (tcl-var-get i "opts")))
+          (not (equal? (tcl-string-first "-code" opts-str 0) "-1")))))
+
+    ; --- catch nested ---
+    (ok "catch-nested"
+      (tcl-var-get (run "catch {catch {error inner} r2} outer") "r2")
+      "inner")
+
+    ; --- return -code error ---
+    (ok "return-code-error-code"
+      (get (run "catch {return -code error oops} r") :result)
+      "1")
+    (ok "return-code-error-val"
+      (tcl-var-get (run "catch {return -code error oops} r") "r")
+      "oops")
+
+    ; --- return -code ok ---
+    (ok "return-code-ok"
+      (get (run "catch {return -code ok hello} r") :result)
+      "0")
+    (ok "return-code-ok-val"
+      (tcl-var-get (run "catch {return -code ok hello} r") "r")
+      "hello")
+
+    ; --- return -code break ---
+    (ok "return-code-break"
+      (get (run "catch {return -code break} r") :result)
+      "3")
+
+    ; --- return -code continue ---
+    (ok "return-code-continue"
+      (get (run "catch {return -code continue} r") :result)
+      "4")
+
+    ; --- return -code numeric ---
+    (ok "return-code-numeric-5"
+      (get (run "catch {return -code 5 msg} r") :result)
+      "5")
+
+    ; --- return plain still code 2 (catch sees raw return code) ---
+    (ok "return-plain-code"
+      (get (run "catch {return hello} r") :result)
+      "2")
+    (ok "return-plain-val"
+      (tcl-var-get (run "catch {return hello} r") "r")
+      "hello")
+
+    ; --- proc return -code error ---
+    (ok "proc-return-code-error"
+      (get (run "proc p {} {return -code error bad}\ncatch {p} r") :result)
+      "1")
+    (ok "proc-return-code-error-val"
+      (tcl-var-get (run "proc p {} {return -code error bad}\ncatch {p} r") "r")
+      "bad")
+
+    ; --- error with info/code args ---
+    (ok? "error-errorinfo-stored"
+      (let
+        ((i (run "catch {error msg myinfo mycode} r")))
+        (= (get i :code) 0)))
+
+    ; --- throw ---
+    (ok "throw-code" (get (run "catch {throw MYERR something} r") :result) "1")
+    (ok "throw-msg" (tcl-var-get (run "catch {throw MYERR something} r") "r") "something")
+
+    ; --- try basic ok ---
+    (ok "try-ok-result"
+      (get (run "try {set x hello} on ok {r} {set r2 $r}") :result)
+      "hello")
+
+    ; --- try on error ---
+    (ok "try-on-error-handled"
+      (get (run "try {error boom} on error {e} {set caught $e}") :result)
+      "boom")
+    (ok "try-on-error-var"
+      (tcl-var-get (run "try {error boom} on error {e} {set caught $e}") "caught")
+      "boom")
+
+    ; --- try finally always runs ---
+    (ok "try-finally-ok"
+      (tcl-var-get (run "try {set x 1} finally {set done yes}") "done")
+      "yes")
+    (ok "try-finally-error"
+      (tcl-var-get (run "catch {try {error boom} finally {set done yes}} r") "done")
+      "yes")
+
+    ; --- try on error + finally ---
+    (ok "try-error-finally"
+      (tcl-var-get
+        (run "try {error oops} on error {e} {set caught $e} finally {set cleaned yes}")
+        "cleaned")
+      "yes")
+    (ok "try-error-finally-caught"
+      (tcl-var-get
+        (run "try {error oops} on error {e} {set caught $e} finally {set cleaned yes}")
+        "caught")
+      "oops")
+
+    ; --- try on ok and on error ---
+    (ok "try-multi-clause-ok"
+      (tcl-var-get
+        (run "try {set x 1} on ok {r} {set which ok} on error {e} {set which err}")
+        "which")
+      "ok")
+    (ok "try-multi-clause-err"
+      (tcl-var-get
+        (run "try {error boom} on ok {r} {set which ok} on error {e} {set which err}")
+        "which")
+      "err")
+
+    ; --- catch preserves output ---
+    (ok "catch-output-preserved"
+      (get (run "puts -nonewline before\ncatch {puts -nonewline inside\nerror oops}\nputs -nonewline after")
+        :output)
+      "beforeinsideafter")
+
+    (dict
+      "passed"
+      tcl-err-pass
+      "failed"
+      tcl-err-fail
+      "failures"
+      tcl-err-failures)))