'main': Avoid triggering a zsh bug related to hashed commands.

This manifested in completion of the form «./foo<TAB>» where there happened to
be a program called 'foo' in $PATH.

Fixes #354.
Closes #355.

highlighters/main/main-highlighter.zsh

@@ -113,7 +113,14 @@ _zsh_highlight_main__type() {
       REPLY=builtin
     elif (( $+commands[(e)$1] )); then
       REPLY=command
-    elif ! builtin type -w -- $1 >/dev/null 2>&1; then
+    # zsh 5.2 and older have a bug whereby running 'type -w ./sudo' implicitly
+    # runs 'hash ./sudo=/usr/local/bin/./sudo' (assuming /usr/local/bin/sudo
+    # exists and is in $PATH).  Avoid triggering the bug, at the expense of
+    # falling through to the $() below, incurring a fork.  (Issue #354.)
+    #
+    # The second disjunct mimics the isrelative() C call from the zsh bug.
+    elif { is-at-least 5.3 || [[ $1 != */* ]] } &&
+         ! builtin type -w -- $1 >/dev/null 2>&1; then
       REPLY=none
     fi
   fi

zsh-syntax-highlighting.zsh

@@ -383,5 +383,7 @@ add-zsh-hook preexec _zsh_highlight_preexec_hook 2>/dev/null || {
 # Load zsh/parameter module if available
 zmodload zsh/parameter 2>/dev/null || true
 
+autoload -U is-at-least
+
 # Initialize the array of active highlighters if needed.
 [[ $#ZSH_HIGHLIGHT_HIGHLIGHTERS -eq 0 ]] && ZSH_HIGHLIGHT_HIGHLIGHTERS=(main) || true