With `const c: cstring` using literal `string` value from `template`, `Error: type mismatch: got 'cstring' for '""' but expected 'string'` #24296

tersec · 2024-10-13T05:47:43Z

Description

# Either changing the template to `proc`/`func` or using `$""`, not a string
# literal alone, allows any version of Nim 2.x to compile this.
template g(): string = ""

# Alternatively: don't retrieve the string through g(), but directly, also
# allows compilation across Nim 2.x versions.
const d: cstring = ""
const f: cstring = $""
const b = cstring g()
const m = cstring ""
const p = cstring $""

# But this does not compile across Nim 2.x/devel.
const c: cstring = g()

Nim Version

Nim Compiler Version 2.0.10 [Linux: amd64]
Compiled at 2024-10-13
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: e941ee15be775fe3c46db1bed9b4f41c7dfb1334
active boot switches: -d:release

Nim Compiler Version 2.2.0 [Linux: amd64]
Compiled at 2024-10-13
Copyright (c) 2006-2024 by Andreas Rumpf

git hash: 78983f1876726a49c69d65629ab433ea1310ece1
active boot switches: -d:release

Nim Compiler Version 2.2.1 [Linux: amd64]
Compiled at 2024-10-13
Copyright (c) 2006-2024 by Andreas Rumpf

git hash: 720d0aee5c2d56260587f9ab09220d18ab9b53f7
active boot switches: -d:release

Current Output

/tmp/u.nim(14, 21) Error: type mismatch: got 'cstring' for '""' but expected 'string'

Expected Output

Builds, or otherwise consistent behavior. Using many minor variations allows the compile-time context to trigger properly, just this one specific way of accessing it triggers this error.

Known Workarounds

No response

Additional Information

Related to #24295 but the method syntax usage seems to have accidentally worked around this through 2.0, until 2.2 (even giving the template a dummy parameter works in 2.0):

template g(x: int): string = ""
const c: cstring = 0.g()

works in 2.0 but not 2.2/devel; see linked issue for more.

This issue points to a broader case which also did not work in 2.0.x.

The text was updated successfully, but these errors were encountered:

ringabout · 2024-10-13T06:50:06Z

It is also a 1.6.12 -> 1.6.14 regression

ringabout · 2024-10-13T06:54:06Z

!nim c

# Either changing the template to `proc`/`func` or using `$""`, not a string
# literal alone, allows any version of Nim 2.x to compile this.
template g(): string = ""

# But this does not compile across Nim 2.x/devel.
const c: cstring = g()

github-actions · 2024-10-13T08:09:11Z

🐧 Linux bisect by @ringabout (member)

devel 👎 FAIL

Output

IR

Compiled filesize 0 (0 bytes)

Stats

Started 2024-10-13T06:54:32
Finished 2024-10-13T06:54:32
Duration

AST

nnkStmtList.newTree(
  nnkTemplateDef.newTree(
    newIdentNode("g"),
    newEmptyNode(),
    newEmptyNode(),
    nnkFormalParams.newTree(
      newIdentNode("string")
    ),
    newEmptyNode(),
    newEmptyNode(),
    nnkStmtList.newTree(
      newLit("")
    )
  ),
  nnkConstSection.newTree(
    nnkConstDef.newTree(
      newIdentNode("c"),
      newIdentNode("cstring"),
      nnkCall.newTree(
        newIdentNode("g")
      )
    )
  )
)

stable 👎 FAIL

Output

IR

Compiled filesize 0 (0 bytes)

Stats

Started 2024-10-13T06:54:36
Finished 2024-10-13T06:54:36
Duration

AST

nnkStmtList.newTree(
  nnkTemplateDef.newTree(
    newIdentNode("g"),
    newEmptyNode(),
    newEmptyNode(),
    nnkFormalParams.newTree(
      newIdentNode("string")
    ),
    newEmptyNode(),
    newEmptyNode(),
    nnkStmtList.newTree(
      newLit("")
    )
  ),
  nnkConstSection.newTree(
    nnkConstDef.newTree(
      newIdentNode("c"),
      newIdentNode("cstring"),
      nnkCall.newTree(
        newIdentNode("g")
      )
    )
  )
)

2.0.10 👎 FAIL

Output

IR

Compiled filesize 0 (0 bytes)

Stats

Started 2024-10-13T06:54:39
Finished 2024-10-13T06:54:39
Duration

AST

nnkStmtList.newTree(
  nnkTemplateDef.newTree(
    newIdentNode("g"),
    newEmptyNode(),
    newEmptyNode(),
    nnkFormalParams.newTree(
      newIdentNode("string")
    ),
    newEmptyNode(),
    newEmptyNode(),
    nnkStmtList.newTree(
      newLit("")
    )
  ),
  nnkConstSection.newTree(
    nnkConstDef.newTree(
      newIdentNode("c"),
      newIdentNode("cstring"),
      nnkCall.newTree(
        newIdentNode("g")
      )
    )
  )
)

2.0.0 👎 FAIL

Output

IR

Compiled filesize 0 (0 bytes)

Stats

Started 2024-10-13T06:54:42
Finished 2024-10-13T06:54:43
Duration

AST

nnkStmtList.newTree(
  nnkTemplateDef.newTree(
    newIdentNode("g"),
    newEmptyNode(),
    newEmptyNode(),
    nnkFormalParams.newTree(
      newIdentNode("string")
    ),
    newEmptyNode(),
    newEmptyNode(),
    nnkStmtList.newTree(
      newLit("")
    )
  ),
  nnkConstSection.newTree(
    nnkConstDef.newTree(
      newIdentNode("c"),
      newIdentNode("cstring"),
      nnkCall.newTree(
        newIdentNode("g")
      )
    )
  )
)

1.6.20 👎 FAIL

Output

IR

Compiled filesize 0 (0 bytes)

Stats

Started 2024-10-13T06:54:45
Finished 2024-10-13T06:54:45
Duration

AST

nnkStmtList.newTree(
  nnkTemplateDef.newTree(
    newIdentNode("g"),
    newEmptyNode(),
    newEmptyNode(),
    nnkFormalParams.newTree(
      newIdentNode("string")
    ),
    newEmptyNode(),
    newEmptyNode(),
    nnkStmtList.newTree(
      newLit("")
    )
  ),
  nnkConstSection.newTree(
    nnkConstDef.newTree(
      newIdentNode("c"),
      newIdentNode("cstring"),
      nnkCall.newTree(
        newIdentNode("g")
      )
    )
  )
)

1.4.8 👍 OK

Output

IR

Compiled filesize 91.16 Kb (93,344 bytes)

#include "nimbase.h"
#define nimfr_(x, y)
#define nimln_(x, y)
static N_INLINE(void, initStackBottomWith)(void* locals);
N_LIB_PRIVATE N_NOINLINE(void, nimGC_setStackBottom)(void* theStackBottom);
N_LIB_PRIVATE N_NIMCALL(void, systemDatInit000)(void);
N_LIB_PRIVATE N_NIMCALL(void, systemInit000)(void);
N_LIB_PRIVATE N_NIMCALL(void, NimMainModule)(void);
static N_INLINE(void, initStackBottomWith)(void* locals) {
 nimGC_setStackBottom(locals);
}
N_LIB_PRIVATE void PreMainInner(void) {
}
N_LIB_PRIVATE int cmdCount;
N_LIB_PRIVATE char** cmdLine;
N_LIB_PRIVATE char** gEnv;
N_LIB_PRIVATE void PreMain(void) {
 void (*volatile inner)(void);
 inner = PreMainInner;
 systemDatInit000();
 initStackBottomWith((void *)&inner);
 systemInit000();
 (*inner)();
}
N_LIB_PRIVATE N_CDECL(void, NimMainInner)(void) {
 NimMainModule();
}
N_CDECL(void, NimMain)(void) {
 void (*volatile inner)(void);
 PreMain();
 inner = NimMainInner;
 initStackBottomWith((void *)&inner);
 (*inner)();
}
int main(int argc, char** args, char** env) {
 cmdLine = args;
 cmdCount = argc;
 gEnv = env;
 NimMain();
 return nim_program_result;
}
N_LIB_PRIVATE N_NIMCALL(void, NimMainModule)(void) {
{
}
}

Stats

Started 2024-10-13T06:54:48
Finished 2024-10-13T06:54:48
Duration

1.2.18 👍 OK

Output

IR

Compiled filesize 86.88 Kb (88,968 bytes)

#include "nimbase.h"
#define nimfr_(x, y)
#define nimln_(x, y)
static N_INLINE(void, initStackBottomWith)(void* locals);
N_LIB_PRIVATE N_NOINLINE(void, nimGC_setStackBottom)(void* theStackBottom);
N_LIB_PRIVATE N_NIMCALL(void, systemDatInit000)(void);
N_LIB_PRIVATE N_NIMCALL(void, systemInit000)(void);
N_LIB_PRIVATE N_NIMCALL(void, NimMainModule)(void);
static N_INLINE(void, initStackBottomWith)(void* locals) {
 nimGC_setStackBottom(locals);
}
N_LIB_PRIVATE void PreMainInner(void) {
}
N_LIB_PRIVATE int cmdCount;
N_LIB_PRIVATE char** cmdLine;
N_LIB_PRIVATE char** gEnv;
N_LIB_PRIVATE void PreMain(void) {
 void (*volatile inner)(void);
 inner = PreMainInner;
 systemDatInit000();
 initStackBottomWith((void *)&inner);
 systemInit000();
 (*inner)();
}
N_LIB_PRIVATE N_CDECL(void, NimMainInner)(void) {
 NimMainModule();
}
N_CDECL(void, NimMain)(void) {
 void (*volatile inner)(void);
 PreMain();
 inner = NimMainInner;
 initStackBottomWith((void *)&inner);
 (*inner)();
}
int main(int argc, char** args, char** env) {
 cmdLine = args;
 cmdCount = argc;
 gEnv = env;
 NimMain();
 return nim_program_result;
}
N_LIB_PRIVATE N_NIMCALL(void, NimMainModule)(void) {
{
}
}

Stats

Started 2024-10-13T06:54:50
Finished 2024-10-13T06:54:51
Duration

1.0.10 👍 OK

Output

IR

Compiled filesize 81.98 Kb (83,952 bytes)

#include "nimbase.h"
#define nimfr_(x, y)
#define nimln_(x, y)
static N_INLINE(void, initStackBottomWith)(void* locals);
N_NOINLINE(void, nimGC_setStackBottom)(void* theStackBottom);
N_LIB_PRIVATE N_NIMCALL(void, systemDatInit000)(void);
N_LIB_PRIVATE N_NIMCALL(void, systemInit000)(void);
N_LIB_PRIVATE N_NIMCALL(void, NimMainModule)(void);
static N_INLINE(void, initStackBottomWith)(void* locals) {	nimGC_setStackBottom(locals);
}
void PreMainInner(void) {
}
int cmdCount;
char** cmdLine;
char** gEnv;
void PreMain(void) {
 void (*volatile inner)(void);
 inner = PreMainInner;
 systemDatInit000();
 initStackBottomWith((void *)&inner);
 systemInit000();
 (*inner)();
}
N_CDECL(void, NimMainInner)(void) {
 NimMainModule();
}
N_CDECL(void, NimMain)(void) {
 void (*volatile inner)(void);
 PreMain();
 inner = NimMainInner;
 initStackBottomWith((void *)&inner);
 (*inner)();
}
int main(int argc, char** args, char** env) {
 cmdLine = args;
 cmdCount = argc;
 gEnv = env;
 NimMain();
 return nim_program_result;
}
N_LIB_PRIVATE N_NIMCALL(void, NimMainModule)(void) {
{
}
}

Stats

Started 2024-10-13T06:54:53
Finished 2024-10-13T06:54:53
Duration

#0014b9c48 ➡️ 🐛

Diagnostics

metagn introduced a bug at 2022-08-24 08:11:41 +0300 on commit #0014b9c48 with message:

top-down type inference, implements rfc 149 (#20091)

* micro implementation of rfc 149

refs https://github.com/nim-lang/RFCs/issues/149

* number/array/seq literals, more statements

* try fix number literal alias issue

* renew expectedType with if/case/try branch types

* fix (nerf) index type handling and float typed int

* use typeAllowed

* tweaks + const test (tested locally) [skip ci]

* fill out more of the checklist

* more literals, change @ order, type conversions

Not copying the full call tree before the typedesc call check
in `semIndirectOp` is also a small performance improvement.

* disable self-conversion warning

* revert type conversions (maybe separate op later)

* deal with CI for now (seems unrelated), try enums

* workaround CI different way

* proper fix

* again

* see sizes

* lol

* overload selection, simplify int literal -> float

* range, new @ solution, try use fitNode for nil

* use new magic

* try fix ranges, new magic, deal with #20193

* add documentation, support templates

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

The bug is in the files:

compiler/ast.nim
compiler/ccgexprs.nim
compiler/condsyms.nim
compiler/jsgen.nim
compiler/sem.nim
compiler/semdata.nim
compiler/semexprs.nim
compiler/semobjconstr.nim
compiler/semstmts.nim
compiler/sizealignoffsetimpl.nim
compiler/varpartitions.nim
compiler/vmgen.nim
doc/manual_experimental.md
lib/pure/collections/sequtils.nim
lib/system.nim
tests/stdlib/tsequtils.nim
tests/types/ttopdowninference.nim

The bug can be in the commits:

(Diagnostics sometimes off-by-one).

Stats

GCC 11.4.0
Clang 14.0.0
NodeJS 20.4
Created 2024-10-13T06:54:06Z
Comments 2
Commands nim c --run -d:nimDebug -d:nimDebugDlOpen -d:ssl -d:nimDisableCertificateValidation --forceBuild:on --colors:off --verbosity:0 --hints:off --lineTrace:off --nimcache:/home/runner/work/Nim/Nim --out:/home/runner/work/Nim/Nim/temp /home/runner/work/Nim/Nim/temp.nim

🤖 Bug found in 40 mins bisecting 4404 commits at 109 commits per second

#24298) fixes #24296 fixes #24295 Templates use `expectedType` for type inference. It's justified that when templates don't have an actual return type, i.e., `untyped` etc. When the return type of templates is specified, we should not infer the type ```nim template g(): string = "" let c: cstring = g() ``` In this example, it is not reasonable to annotate the templates expression with the `cstring` type before the `fitNode` check with its specified return type. (cherry picked from commit 80e6b35)

ringabout mentioned this issue Oct 13, 2024

templates/macros use no expected types when return types are specified #24298

Merged

Araq closed this as completed in #24298 Oct 13, 2024

Araq closed this as completed in 80e6b35 Oct 13, 2024

tersec mentioned this issue Dec 8, 2024

Nim version codex-storage/nim-codex#1011

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With `const c: cstring` using literal `string` value from `template`, `Error: type mismatch: got 'cstring' for '""' but expected 'string'` #24296

With `const c: cstring` using literal `string` value from `template`, `Error: type mismatch: got 'cstring' for '""' but expected 'string'` #24296

tersec commented Oct 13, 2024

ringabout commented Oct 13, 2024

ringabout commented Oct 13, 2024

github-actions bot commented Oct 13, 2024

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Diagnostics

With const c: cstring using literal string value from template, Error: type mismatch: got 'cstring' for '""' but expected 'string' #24296

With const c: cstring using literal string value from template, Error: type mismatch: got 'cstring' for '""' but expected 'string' #24296

Comments

tersec commented Oct 13, 2024

Description

Nim Version

Current Output

Expected Output

Known Workarounds

Additional Information

ringabout commented Oct 13, 2024

ringabout commented Oct 13, 2024

github-actions bot commented Oct 13, 2024

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Diagnostics

With `const c: cstring` using literal `string` value from `template`, `Error: type mismatch: got 'cstring' for '""' but expected 'string'` #24296

With `const c: cstring` using literal `string` value from `template`, `Error: type mismatch: got 'cstring' for '""' but expected 'string'` #24296