Add SC1133: Warn when a line starts with |/||/&& (fixes #1359)

CHANGELOG.md

@@ -5,6 +5,7 @@
 - SC2236/SC2237: Suggest -n/-z instead of ! -z/-n
 - SC2238: Warn when redirecting to a known command name, e.g. ls > rm
 - SC2239: Warn if the shebang is not an absolute path, e.g. #!bin/sh
+- SC1133: Better diagnostics when starting a line with |/||/&&
 ### Changed
 - Most warnings now have useful end positions
 - SC1117 about unknown double-quoted escape sequences has been retired

src/ShellCheck/Parser.hs

@@ -1911,7 +1911,13 @@ readHereString = called "here string" $ do
     word <- readNormalWord
     return $ T_HereString id word
 
-readNewlineList = many1 ((linefeed <|> carriageReturn) `thenSkip` spacing)
+readNewlineList =
+    many1 ((linefeed <|> carriageReturn) `thenSkip` spacing) <* checkBadBreak
+  where
+    checkBadBreak = optional $ do
+                pos <- getPosition
+                try $ lookAhead (oneOf "|&") -- |, || or &&
+                parseProblemAt pos ErrorC 1133 "Unexpected start of line. If breaking lines, |/||/&& should be at the end of the previous one."
 readLineBreak = optional readNewlineList
 
 prop_readSeparator1 = isWarning readScript "a &; b"
@@ -2300,7 +2306,7 @@ readSubshell = called "explicit subshell" $ do
     allspacing
     list <- readCompoundList
     allspacing
-    char ')' <|> fail ") closing the subshell"
+    char ')' <|> fail "Expected ) closing the subshell"
     id <- endSpan start
     return $ T_Subshell id list