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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2012-01-12 15:10:54 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2012-01-12 15:10:54 +0000 |
| commit | 5508ada4b1d90ee54d92f69bbff7f66b3e8eceef (patch) | |
| tree | 302bb0c73f96faf9249521b5baf0d879fe11fd6f /compiler/parser/Lexer.x | |
| parent | b8fe21e9ba5486256c83784ca8b9a839b5c527f4 (diff) | |
| download | haskell-5508ada4b1d90ee54d92f69bbff7f66b3e8eceef.tar.gz | |
Implememt -fdefer-type-errors (Trac #5624)
This patch implements the idea of deferring (most) type errors to
runtime, instead emitting only a warning at compile time. The
basic idea is very simple:
* The on-the-fly unifier in TcUnify never fails; instead if it
gets stuck it emits a constraint.
* The constraint solver tries to solve the constraints (and is
entirely unchanged, hooray).
* The remaining, unsolved constraints (if any) are passed to
TcErrors.reportUnsolved. With -fdefer-type-errors, instead of
emitting an error message, TcErrors emits a warning, AND emits
a binding for the constraint witness, binding it
to (error "the error message"), via the new form of evidence
TcEvidence.EvDelayedError. So, when the program is run,
when (and only when) that witness is needed, the program will
crash with the exact same error message that would have been
given at compile time.
Simple really. But, needless to say, the exercise forced me
into some major refactoring.
* TcErrors is almost entirely rewritten
* EvVarX and WantedEvVar have gone away entirely
* ErrUtils is changed a bit:
* New Severity field in ErrMsg
* Renamed the type Message to MsgDoc (this change
touches a lot of files trivially)
* One minor change is that in the constraint solver we try
NOT to combine insoluble constraints, like Int~Bool, else
all such type errors get combined together and result in
only one error message!
* I moved some definitions from TcSMonad to TcRnTypes,
where they seem to belong more
Diffstat (limited to 'compiler/parser/Lexer.x')
| -rw-r--r-- | compiler/parser/Lexer.x | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/compiler/parser/Lexer.x b/compiler/parser/Lexer.x index 21984eced9..e0e97fed4a 100644 --- a/compiler/parser/Lexer.x +++ b/compiler/parser/Lexer.x @@ -145,7 +145,7 @@ haskell :- -- everywhere: skip whitespace and comments $white_no_nl+ ; -$tab+ { warn Opt_WarnTabs (text "Warning: Tab character") } +$tab+ { warn Opt_WarnTabs (text "Tab character") } -- Everywhere: deal with nested comments. We explicitly rule out -- pragmas, "{-#", so that we don't accidentally treat them as comments. @@ -1484,7 +1484,7 @@ data ParseResult a SrcSpan -- The start and end of the text span related to -- the error. Might be used in environments which can -- show this span, e.g. by highlighting it. - Message -- The error message + MsgDoc -- The error message data PState = PState { buffer :: StringBuffer, @@ -1959,7 +1959,7 @@ getOffside = P $ \s@PState{last_loc=loc, context=stk} -> srcParseErr :: StringBuffer -- current buffer (placed just after the last token) -> Int -- length of the previous token - -> Message + -> MsgDoc srcParseErr buf len = hcat [ if null token then ptext (sLit "parse error (possibly incorrect indentation)") |