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* ADR-029 callback typing: E0879, E0880.
*
* #1322. Two throws in `TypeValidator`, reached from `AssignmentValidator`
* for exactly one target shape -- `h.down <- f`, a variable's direct field --
* and reported as `1:0`. A function is a type under ADR-029, so a function
* NAMED as a value must fit the slot it is placed in: its signature must
* match the slot's type (E0879), and a function that is itself used as a
* field type is nominally distinct from every other (E0880). A variable of
* callback type placed in a slot is not named here: it already carries its
* type, and codegen never asked; stated below.
*
* ## Four slots, one rule
*
* The rule is about where a function name lands, and codegen checked one of
* the four places it can:
*
* - an assignment, `h.down <- f` -- checked, for a direct field only;
* `this.h.down`, `a.b.down` and a callback-typed variable never reached it
* - a declaration's initializer, `onDown cb <- f`
* - a struct initializer's field, `{ down: f }`
* - a call's argument, `register(f)` -- the case ADR-029's own example marks
* `COMPILE ERROR`
*
* All four are decided here, from the slot's declared type through the same
* lookup (`FunctionReference`), at the value's own position.
*
* ## What "used as a field type" reads
*
* Codegen's nominal rule read a map filled while emitting struct
* declarations, so it held the structs emitted so far in the CURRENT file:
* a struct declared below the assignment, in an enclosing scope, or in an
* include did not count. The per-file symbol view holds every struct this
* file can see, and that is what a type identity is.
*
* ## Stated, not closed
*
* A function used only as a PARAMETER type (`void reg(onUp cb)`) is not a
* nominal type here, as it was not in codegen; widening that is a language
* decision (ADR-029 §Nominal Typing names struct fields). Array dimensions of
* parameters are not compared, as they were not.
*/
import { ParserRuleContext, ParseTreeWalker } from "antlr4ng";
import { CNextListener } from "../../PARSE/2-Parse/grammar/CNextListener";
import * as Parser from "../../PARSE/2-Parse/grammar/CNextParser";
import IFunctionSymbol from "../../types/symbols/IFunctionSymbol";
import ParserUtils from "../../utils/ParserUtils";
import TypeResolver from "../../utils/TypeResolver";
import OperandTyper from "../../utils/OperandTyper";
import FunctionReference from "./helpers/FunctionReference";
import StructInitializerType from "./helpers/StructInitializerType";
import AssignmentSiteListener from "./AssignmentSiteListener";
import ICallbackAssignmentError from "./types/ICallbackAssignmentError";
import type IAnalysisContext from "./types/IAnalysisContext";
import type TAssignmentSite from "./types/TAssignmentSite";
/** Where a function name landed, for the message. */
interface ISlot {
readonly verb: "assign" | "pass";
readonly description: string;
}
class CallbackAssignmentListener extends CNextListener {
private readonly found: ICallbackAssignmentError[] = [];
private fieldTypes: ReadonlySet<string> | null = null;
public constructor(private readonly context: IAnalysisContext) {
super();
}
public errors(): ICallbackAssignmentError[] {
return this.found;
}
/** `target <- f`, any target shape, in a statement or a `for` header */
public checkSite(site: TAssignmentSite): void {
const target = site.assignmentTarget();
const description = CallbackAssignmentListener.describeTarget(target);
this.check(
OperandTyper.typeOfTarget(target, this.context)?.typeName ?? null,
site.expression(),
{ verb: "assign", description },
);
}
/** `onDown cb <- f`, in a function, a scope, at file scope. */
override enterVariableDeclaration = (
ctx: Parser.VariableDeclarationContext,
): void => {
this.checkDeclaration(ctx.type(), ctx.IDENTIFIER(), ctx.expression());
};
/** `for (onDown cb <- f; ...)`. */
override enterForVarDecl = (ctx: Parser.ForVarDeclContext): void => {
this.checkDeclaration(ctx.type(), ctx.IDENTIFIER(), ctx.expression());
};
/** `{ down: f }`, wherever the initializer's struct is established. */
override enterFieldInitializer = (
ctx: Parser.FieldInitializerContext,
): void => {
const init = ctx.parent?.parent;
Iif (!(init instanceof Parser.StructInitializerContext)) return;
const structName = StructInitializerType.of(init, this.context);
if (structName === null) return;
const fieldName = ctx.IDENTIFIER().getText();
this.check(
this.context.symbols.structFields.get(structName)?.get(fieldName) ?? null,
ctx.expression(),
{ verb: "assign", description: `callback field '${fieldName}'` },
);
};
/** `register(f)`: each argument against its parameter's type. */
override enterPostfixExpression = (
ctx: Parser.PostfixExpressionContext,
): void => {
const call = ctx.postfixOp().find((op) => op.LPAREN() !== null);
if (call === undefined) return;
const callee = FunctionReference.ofCall(
ctx,
OperandTyper.scopePathAt(ctx, this.context),
this.context,
);
if (callee === null) return;
const args = call.argumentList()?.expression() ?? [];
args.forEach((arg, index) => {
const param = callee.parameters[index];
Iif (param === undefined) return;
this.check(TypeResolver.getTypeName(param.type), arg, {
verb: "pass",
description: `parameter '${param.name}' of function '${callee.name}'`,
});
});
};
/** How an assignment target is named in a message. */
private static describeTarget(
target: Parser.AssignmentTargetContext,
): string {
const last = target.postfixTargetOp().at(-1);
if (last === undefined) {
return `callback variable '${target.getText()}'`;
}
if (last.DOT() !== null) {
return `callback field '${last.IDENTIFIER()?.getText()}'`;
}
return `callback '${target.getText()}'`;
}
private checkDeclaration(
typeCtx: Parser.TypeContext | null,
identifier: { getText(): string } | null,
initializer: Parser.ExpressionContext | null,
): void {
if (!typeCtx || !identifier || !initializer) return;
this.check(typeCtx.getText(), initializer, {
verb: "assign",
description: `callback variable '${identifier.getText()}'`,
});
}
/**
* The rule. Silent unless the slot's type is a function AND the value
* names one; then the signatures must match, and a value that is itself a
* field type must be the slot's own.
*/
private check(
slotTypeText: string | null,
value: Parser.ExpressionContext,
slot: ISlot,
): void {
Iif (slotTypeText === null) return;
const scopePath = OperandTyper.scopePathAt(value, this.context);
const expected = FunctionReference.ofTypeText(
slotTypeText,
scopePath,
this.context,
);
if (expected === null) return;
const actual = FunctionReference.ofValue(value, scopePath, this.context);
Iif (actual === null) return;
const valueText = value.getText();
if (!CallbackAssignmentListener.signaturesMatch(expected, actual)) {
this.report(
value,
"E0879",
`Function '${valueText}' signature does not match callback type '${slotTypeText}'`,
"A callback must match its type's signature exactly: return type, parameter count, and each parameter's type, const-ness and array-ness (ADR-029).",
);
return;
}
const actualName = FunctionReference.cNameOf(actual);
if (
actualName !== FunctionReference.cNameOf(expected) &&
this.isFieldType(actualName)
) {
const verb =
slot.verb === "assign"
? `Cannot assign '${valueText}' to`
: `Cannot pass '${valueText}' as`;
this.report(
value,
"E0880",
`${verb} ${slot.description} (expected ${slotTypeText} type, got ${valueText} type - nominal typing)`,
"A function used as a struct field's type is its own callback type; only a function that is not itself a type may stand in for another (ADR-029).",
);
}
}
/**
* Whether any struct in the program declares a field of this type -- what
* makes a function a nominal callback type rather than a plain function.
*
* Asked of the PROGRAM, not of the per-file view, and that is the decision.
* ADR-029 says "type identity is the function name": a function IS a type
* because some struct declares a field of it, which is a property of the
* program and not of who imported whom. Reading a per-file set would make
* the same function nominal in one file and plain in another, so the same
* assignment would be rejected or accepted depending on the include graph.
*
* This is deliberately the opposite choice from #1398's VISIBILITY question
* (E0427), where the run-wide table is wrong because a sibling that was
* never included must not resolve. Here the function is visible either way
* -- it was named in the source -- and the only question is what its type
* identity is.
*
* Codegen asked `CodeGenState.callbackFieldTypes`, which holds the structs
* emitted SO FAR in the current file, so a struct declared below the
* assignment, in an enclosing scope, or in an include did not count.
*/
private isFieldType(cName: string): boolean {
this.fieldTypes ??= this.collectFieldTypes();
return this.fieldTypes.has(cName);
}
private collectFieldTypes(): ReadonlySet<string> {
return new Set([
...this.fieldTypesInFileView(),
...this.fieldTypesInProgram(),
]);
}
/** Field types of the structs this file declares. */
private fieldTypesInFileView(): string[] {
const types: string[] = [];
for (const fields of this.context.symbols.structFields.values()) {
types.push(...fields.values());
}
return types;
}
/** Field types of every struct the program declares, in any file. */
private fieldTypesInProgram(): string[] {
const program = this.context.program;
const types: string[] = [];
for (const sourceFile of program.sourceFiles()) {
for (const symbol of program.symbolsInFile(sourceFile)) {
if (symbol.kind !== "struct") continue;
for (const field of symbol.fields.values()) {
types.push(TypeResolver.getTypeName(field.type));
}
}
}
return types;
}
private static signaturesMatch(
a: IFunctionSymbol,
b: IFunctionSymbol,
): boolean {
Iif (
TypeResolver.getTypeName(a.returnType) !==
TypeResolver.getTypeName(b.returnType)
) {
return false;
}
Iif (a.parameters.length !== b.parameters.length) return false;
return a.parameters.every((pa, i) => {
const pb = b.parameters[i];
return (
TypeResolver.getTypeName(pa.type) ===
TypeResolver.getTypeName(pb.type) &&
pa.isConst === pb.isConst &&
pa.isArray === pb.isArray
);
});
}
private report(
at: ParserRuleContext,
code: string,
message: string,
helpText: string,
): void {
const { line, column } = ParserUtils.getPosition(at);
this.found.push({ code, line, column, message, helpText });
}
}
class CallbackAssignmentAnalyzer {
/** #1456: handed in rather than read off shared state. */
constructor(private readonly context: IAnalysisContext) {}
public analyze(tree: Parser.ProgramContext): ICallbackAssignmentError[] {
const listener = new CallbackAssignmentListener(this.context);
ParseTreeWalker.DEFAULT.walk(listener, tree);
ParseTreeWalker.DEFAULT.walk(
new AssignmentSiteListener((site) => listener.checkSite(site)),
tree,
);
// Reported in source order, as the one walk these replace did
return listener
.errors()
.sort((a, b) => a.line - b.line || a.column - b.column);
}
}
export default CallbackAssignmentAnalyzer;
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