Add "intro" to LSP, improve error locations

src/Lib/Elab.newt

@@ -999,13 +999,12 @@ mkPat (tm, icit) = do
                   pure $ PatCon (getFC tm) icit name bpat Nothing
                 -- This fires when a global is shadowed by a pattern var
                 -- Just _ => error (getFC tm) "\{show nm} is not a data constructor"
-                _ => case b of
-                    -- TODO maybe check case?
-                    Nil =>
-                      if isUpperName nm
+                _ => if isUpperName nm
+                        -- This is not entirely accurate - it could be a function def
                         then error (getFC tm) "\{nm} not in scope"
-                        else pure $ PatVar fc icit nm
-                    _ => error (getFC tm) "patvar applied to args"
+                        else case b of
+                          Nil => pure $ PatVar fc icit nm
+                          _ => error (getFC tm) "patvar applied to args"
     ((RImplicit fc), Nil) => pure $ PatWild fc icit
     ((RImplicit fc), _) => error fc "implicit pat can't be applied to arguments"
     ((RLit fc lit), Nil) => pure $ PatLit fc lit
@@ -1486,9 +1485,10 @@ check ctx tm ty = do
                 pure $ Lam fc nm' icit rig sc
               else
                 error fc "Icity issue checking \{show t} at \{show ty}"
-    (t@(RLam _ (BI fc nm icit quant) tm), ty) => do
+    (t@(RLam fc (BI _ nm icit quant) tm), ty) => do
               pty <- prvalCtx ty
-              error fc "Expected \{pty}, got pi type"
+              -- TODO I'm hitting this with an unsolved meta
+              error fc "Expected \{pty}, got a function"
 
     (RLet fc nm ty v sc, rty) => do
       ty' <- check ctx ty (VU emptyFC)
@@ -1513,7 +1513,6 @@ check ctx tm ty = do
       pure $ Lam (getFC tm) nm' Implicit rig sc
 
     (tm, ty@(VPi fc nm' Auto rig a b)) => do
-      let names = map fst ctx.types
       debug $ \ _ => "XXX edge case add auto lambda {\{nm'} : \{show a}} to \{show tm} "
       let var = VVar fc (length' ctx.env) Lin
       ty' <- b $$ var

src/Lib/Parser.newt

@@ -311,14 +311,16 @@ pLamArg = impArg <|> autoArg <|> expArg
 lamExpr : Parser Raw
 lamExpr = do
   pos <- getPos
-  keyword "\\" <|> keyword "λ"
-  args <- some $ addPos pLamArg
-  keyword "=>"
-  scope <- typeExpr
-  pure $ foldr mkLam scope args
+  (fc, args, scope) <- withFC $ do
+    keyword "\\" <|> keyword "λ"
+    args <- some $ addPos pLamArg
+    keyword "=>"
+    scope <- typeExpr
+    pure (args, scope)
+  pure $ foldr (mkLam fc) scope args
   where
-    mkLam : FC × Icit × Name × Maybe Raw → Raw → Raw
-    mkLam (fc, icit, name, ty) sc = RLam fc (BI fc name icit Many) sc
+    mkLam : FC → FC × Icit × Name × Maybe Raw → Raw → Raw
+    mkLam fc (nfc, icit, name, ty) sc = RLam fc (BI nfc name icit Many) sc
 
 
 caseAlt : Parser RCaseAlt
@@ -566,10 +568,11 @@ parseDef = do
   nm <- getName t
   Just _ <- optional $ keyword "="
     -- impossible clause
+    -- TODO we should require outdent
     | Nothing => pure $ FunDef fc nm ((t,Nothing) :: Nil)
+  -- TODO could we recover and keep the LHS?
   body <- typeExpr
-  wfc <- getPos
-  w <- optional $ do
+  (wfc, w) <- withFC $ optional $ do
     keyword "where"
     startBlock $ manySame $ (parseSig <|> parseDef)
   let body = maybe body (\ decls => RWhere wfc decls body) w