feat: reject variables declared with a PROGRAM type (E142)#1802
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Programs are singletons: the compiler allocates exactly one global instance per program, and calls by name operate on that instance. Declaring a variable of a program type created a detached copy of the singleton's state, which calls would mutate while the real instance never advances. IEC 61131-3 only allows program instantiation inside CONFIGURATION/RESOURCE declarations, which are not supported. Variable declarations (all VAR blocks, VAR_GLOBAL, struct members, and arrays) whose effective type resolves to a PROGRAM POU now report E142. Direct calls (`myProg(...)`) and member access (`myProg.out1`) on the program name keep working. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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What
Declaring a variable whose type is a
PROGRAMis now a validation error (E142):Why
Programs are singletons — the compiler allocates exactly one global instance per program, and calling a program by name operates on that instance. A program-typed variable silently created a detached copy of the singleton's state: calls through it mutated the copy while the real program instance never advanced. IEC 61131-3 only allows program instantiation inside
CONFIGURATION/RESOURCE, which are not supported.Notes
VAR,VAR_INPUT,VAR_OUTPUT,VAR_IN_OUT,VAR_TEMP,VAR_GLOBAL), struct members, and arrays of a program type.myProg(in1 := 5);) and member access (x := myProg.out1;) on the program name keep working — both are pinned with tests.E142with documentation (plc explain E142).🤖 Generated with Claude Code