Merge pull request #9753 from 9999years/print-value-on-type-error

Print the value in `value is X while a Y is expected` error

(cherry picked from commit 5f72a97092da6af28a7d2b2a50d74e9d34fae7e1)
Change-Id: Idb4bc903ae59a0f5b6fb3b1da4d47970fe0a6efe

1 files changed, 30 insertions, 8 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 729b17887..5e511f49b 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -2,6 +2,7 @@
 #include "eval-settings.hh"
 #include "hash.hh"
 #include "primops.hh"
+#include "print-options.hh"
 #include "types.hh"
 #include "util.hh"
 #include "store-api.hh"
@@ -24,9 +25,9 @@
 #include <unistd.h>
 #include <sys/time.h>
 #include <sys/resource.h>
-#include <iostream>
 #include <fstream>
 #include <functional>
+#include <iostream>
 
 #include <sys/resource.h>
 #include <nlohmann/json.hpp>
@@ -1173,7 +1174,10 @@ inline bool EvalState::evalBool(Env & env, Expr * e, const PosIdx pos, std::stri
         Value v;
         e->eval(*this, env, v);
         if (v.type() != nBool)
-            error("value is %1% while a Boolean was expected", showType(v)).withFrame(env, *e).debugThrow<TypeError>();
+            error("expected a Boolean but found %1%: %2%",
+                  showType(v),
+                  ValuePrinter(*this, v, errorPrintOptions))
+                .withFrame(env, *e).debugThrow<TypeError>();
         return v.boolean;
     } catch (Error & e) {
         e.addTrace(positions[pos], errorCtx);
@@ -1187,7 +1191,10 @@ inline void EvalState::evalAttrs(Env & env, Expr * e, Value & v, const PosIdx po
     try {
         e->eval(*this, env, v);
         if (v.type() != nAttrs)
-            error("value is %1% while a set was expected", showType(v)).withFrame(env, *e).debugThrow<TypeError>();
+            error("expected a set but found %1%: %2%",
+                  showType(v),
+                  ValuePrinter(*this, v, errorPrintOptions))
+                .withFrame(env, *e).debugThrow<TypeError>();
     } catch (Error & e) {
         e.addTrace(positions[pos], errorCtx);
         throw;
@@ -2096,7 +2103,10 @@ NixInt EvalState::forceInt(Value & v, const PosIdx pos, std::string_view errorCt
     try {
         forceValue(v, pos);
         if (v.type() != nInt)
-            error("value is %1% while an integer was expected", showType(v)).debugThrow<TypeError>();
+            error("expected an integer but found %1%: %2%",
+                  showType(v),
+                  ValuePrinter(*this, v, errorPrintOptions))
+                .debugThrow<TypeError>();
         return v.integer;
     } catch (Error & e) {
         e.addTrace(positions[pos], errorCtx);
@@ -2112,7 +2122,10 @@ NixFloat EvalState::forceFloat(Value & v, const PosIdx pos, std::string_view err
         if (v.type() == nInt)
             return v.integer;
         else if (v.type() != nFloat)
-            error("value is %1% while a float was expected", showType(v)).debugThrow<TypeError>();
+            error("expected a float but found %1%: %2%",
+                  showType(v),
+                  ValuePrinter(*this, v, errorPrintOptions))
+                .debugThrow<TypeError>();
         return v.fpoint;
     } catch (Error & e) {
         e.addTrace(positions[pos], errorCtx);
@@ -2126,7 +2139,10 @@ bool EvalState::forceBool(Value & v, const PosIdx pos, std::string_view errorCtx
     try {
         forceValue(v, pos);
         if (v.type() != nBool)
-            error("value is %1% while a Boolean was expected", showType(v)).debugThrow<TypeError>();
+            error("expected a Boolean but found %1%: %2%",
+                  showType(v),
+                  ValuePrinter(*this, v, errorPrintOptions))
+                .debugThrow<TypeError>();
         return v.boolean;
     } catch (Error & e) {
         e.addTrace(positions[pos], errorCtx);
@@ -2146,7 +2162,10 @@ void EvalState::forceFunction(Value & v, const PosIdx pos, std::string_view erro
     try {
         forceValue(v, pos);
         if (v.type() != nFunction && !isFunctor(v))
-            error("value is %1% while a function was expected", showType(v)).debugThrow<TypeError>();
+            error("expected a function but found %1%: %2%",
+                  showType(v),
+                  ValuePrinter(*this, v, errorPrintOptions))
+                .debugThrow<TypeError>();
     } catch (Error & e) {
         e.addTrace(positions[pos], errorCtx);
         throw;
@@ -2159,7 +2178,10 @@ std::string_view EvalState::forceString(Value & v, const PosIdx pos, std::string
     try {
         forceValue(v, pos);
         if (v.type() != nString)
-            error("value is %1% while a string was expected", showType(v)).debugThrow<TypeError>();
+            error("expected a string but found %1%: %2%",
+                  showType(v),
+                  ValuePrinter(*this, v, errorPrintOptions))
+                .debugThrow<TypeError>();
         return v.string.s;
     } catch (Error & e) {
         e.addTrace(positions[pos], errorCtx);