From 87523928389227fa39803e363e10d95ea7c2376e Mon Sep 17 00:00:00 2001 From: metagn Date: Fri, 23 May 2025 17:19:13 +0300 Subject: [PATCH] implement setter fallback for subscripts (#24872) follows up #24871 For subscript assignments, if an overload of `[]=`/`{}=` is not found, the LHS checks for overloads of `[]`/`{}` as a fallback, similar to what field setters do since #24871. This is accomplished by just compiling the LHS if the assignment overloads fail. This has the side effect that the error messages are different now, instead of displaying the overloads of `[]=`/`{}=` that did not match, it will display the ones for `[]`/`{}` instead. This could be fixed by checking for `efLValue` when giving the error messages for `[]`/`{}` but this is not done here. The code for `[]` subscripts is a little different because of the `mArrGet`/`mArrPut` overloads that always match. If the `mArrPut` overload matches without a builtin subscript behavior for the LHS then it calls `semAsgn` again with `mode = noOverloadedSubscript`. Before this meant "fail to compile" but now it means "try to compile the LHS as normal", in both cases the overloads of `[]=` are not considered again. --- compiler/semexprs.nim | 23 +++++-- tests/errmsgs/t22753.nim | 65 ++++++++++--------- tests/specialops/tsetterfallbacksubscript.nim | 25 +++++++ 3 files changed, 79 insertions(+), 34 deletions(-) create mode 100644 tests/specialops/tsetterfallbacksubscript.nim diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim index 5e2a5d0a72..6cc29bd86f 100644 --- a/compiler/semexprs.nim +++ b/compiler/semexprs.nim @@ -1963,21 +1963,34 @@ proc semAsgn(c: PContext, n: PNode; mode=asgnNormal): PNode = of nkBracketExpr: # a[i] = x # --> `[]=`(a, i, x) + # try builtin subscript for LHS first: a = semSubscript(c, a, {efLValue}) if a == nil: - result = buildOverloadedSubscripts(n[0], getIdent(c.cache, "[]=")) - result.add(n[1]) if mode == noOverloadedSubscript: - bracketNotFoundError(c, result, {}) - return errorNode(c, n) + # `[]=` overloads failed and builtin subscript failed, try `[]` overloads for LHS + # will error if not found: + a = semExprWithType(c, n[0], {efLValue}) else: + # magic overload of `[]=` will always match so cannot check for mismatch here, + # will go to above `if` branch instead + result = buildOverloadedSubscripts(n[0], getIdent(c.cache, "[]=")) + result.add(n[1]) result = semExprNoType(c, result) return result of nkCurlyExpr: # a{i} = x --> `{}=`(a, i, x) + # no builtin behavior/magic overloads for curly subscript, + # try `{}=` overloads first then try `{}` overloads for LHS: + let nOrig = n.copyTree result = buildOverloadedSubscripts(n[0], getIdent(c.cache, "{}=")) result.add(n[1]) - return semExprNoType(c, result) + result = semOverloadedCallAnalyseEffects(c, result, result.copyTree, {efNoUndeclared}) + if result != nil: + result = afterCallActions(c, result, nOrig, {}) + return + else: + # will error if `{}` overloads not found: + a = semExprWithType(c, a, {efLValue}) of nkPar, nkTupleConstr: if a.len >= 2 or a.kind == nkTupleConstr: # unfortunately we need to rewrite ``(x, y) = foo()`` already here so diff --git a/tests/errmsgs/t22753.nim b/tests/errmsgs/t22753.nim index 8a504109a8..39f018dd9b 100644 --- a/tests/errmsgs/t22753.nim +++ b/tests/errmsgs/t22753.nim @@ -1,50 +1,57 @@ discard """ cmd: "nim check --hints:off $file" -errormsg: "type mismatch" +action: "reject" nimoutFull: true nimout: ''' -t22753.nim(51, 13) Error: array expects two type parameters -t22753.nim(52, 1) Error: expression 'x' has no type (or is ambiguous) -t22753.nim(52, 1) Error: expression 'x' has no type (or is ambiguous) -t22753.nim(52, 2) Error: type mismatch: got <> +t22753.nim(58, 13) Error: array expects two type parameters +t22753.nim(59, 1) Error: expression 'x' has no type (or is ambiguous) +t22753.nim(59, 1) Error: expression 'x' has no type (or is ambiguous) +t22753.nim(59, 1) Error: expression 'x' has no type (or is ambiguous) +t22753.nim(59, 1) Error: expression 'x' has no type (or is ambiguous) +t22753.nim(59, 2) Error: type mismatch: got <> but expected one of: -proc `[]=`(s: var string; i: BackwardsIndex; x: char) +proc `[]`(s: string; i: BackwardsIndex): char first type mismatch at position: 2 required type for i: BackwardsIndex but expression '0' is of type: int literal(0) -proc `[]=`[I: Ordinal; T, S](a: T; i: I; x: sink S) +proc `[]`(s: var string; i: BackwardsIndex): var char + first type mismatch at position: 2 + required type for i: BackwardsIndex + but expression '0' is of type: int literal(0) +proc `[]`[I: Ordinal; T](a: T; i: I): T first type mismatch at position: 0 -proc `[]=`[Idx, T; U, V: Ordinal](a: var array[Idx, T]; x: HSlice[U, V]; - b: openArray[T]) +proc `[]`[Idx, T; U, V: Ordinal](a: array[Idx, T]; x: HSlice[U, V]): seq[T] first type mismatch at position: 2 - required type for x: HSlice[[]=.U, []=.V] + required type for x: HSlice[[].U, [].V] but expression '0' is of type: int literal(0) -proc `[]=`[Idx, T](a: var array[Idx, T]; i: BackwardsIndex; x: T) +proc `[]`[Idx, T](a: array[Idx, T]; i: BackwardsIndex): T first type mismatch at position: 2 required type for i: BackwardsIndex but expression '0' is of type: int literal(0) -proc `[]=`[T, U: Ordinal](s: var string; x: HSlice[T, U]; b: string) - first type mismatch at position: 2 - required type for x: HSlice[[]=.T, []=.U] - but expression '0' is of type: int literal(0) -proc `[]=`[T; U, V: Ordinal](s: var seq[T]; x: HSlice[U, V]; b: openArray[T]) - first type mismatch at position: 2 - required type for x: HSlice[[]=.U, []=.V] - but expression '0' is of type: int literal(0) -proc `[]=`[T](s: var openArray[T]; i: BackwardsIndex; x: T) +proc `[]`[Idx, T](a: var array[Idx, T]; i: BackwardsIndex): var T + first type mismatch at position: 2 + required type for i: BackwardsIndex + but expression '0' is of type: int literal(0) +proc `[]`[T, U: Ordinal](s: string; x: HSlice[T, U]): string + first type mismatch at position: 2 + required type for x: HSlice[[].T, [].U] + but expression '0' is of type: int literal(0) +proc `[]`[T; U, V: Ordinal](s: openArray[T]; x: HSlice[U, V]): seq[T] + first type mismatch at position: 2 + required type for x: HSlice[[].U, [].V] + but expression '0' is of type: int literal(0) +proc `[]`[T](s: openArray[T]; i: BackwardsIndex): T + first type mismatch at position: 2 + required type for i: BackwardsIndex + but expression '0' is of type: int literal(0) +proc `[]`[T](s: var openArray[T]; i: BackwardsIndex): var T first type mismatch at position: 2 required type for i: BackwardsIndex but expression '0' is of type: int literal(0) -template `[]=`(a: WideCStringObj; idx: int; val: Utf16Char) - first type mismatch at position: 3 - required type for val: Utf16Char - but expression '9' is of type: int literal(9) -template `[]=`(s: string; i: int; val: char) - first type mismatch at position: 3 - required type for val: char - but expression '9' is of type: int literal(9) -expression: x[0] = 9 +expression: x[0] +t22753.nim(59, 2) Error: expression '' has no type (or is ambiguous) +t22753.nim(59, 2) Error: '' cannot be assigned to ''' """ diff --git a/tests/specialops/tsetterfallbacksubscript.nim b/tests/specialops/tsetterfallbacksubscript.nim new file mode 100644 index 0000000000..eb04e1b9f6 --- /dev/null +++ b/tests/specialops/tsetterfallbacksubscript.nim @@ -0,0 +1,25 @@ +type Foo = object + x, y: float + +proc `[]`(foo: var Foo, i: int): var float = + if i == 0: + result = foo.x + else: + result = foo.y + +var pt = Foo(x: 0.0, y: 0.0) +pt[0] += 1.0 # <-- fine +`[]`(pt, 0) = 1.0 # <-- fine +pt[0] = 1.0 # <-- does not compile + +# curly: + +proc `{}`(foo: var Foo, i: int): var float = + if i == 0: + result = foo.x + else: + result = foo.y + +pt{0} += 1.0 # <-- fine +`{}`(pt, 0) = 1.0 # <-- fine +pt{0} = 1.0 # <-- does not compile