docs(input): document array and member targets

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

4 files changed, 34 insertions, 13 deletions

diff --git a/AGENTS/PITFALLS.md b/AGENTS/PITFALLS.md
index dacf106..d604504 100644
--- a/AGENTS/PITFALLS.md
+++ b/AGENTS/PITFALLS.md
@@ -8,8 +8,10 @@ test programs.
 - **OUTPUT accepts comma-separated expressions (§5.1).** Values are evaluated and
   printed left to right without automatic separators; the final scalar adds a newline.
   Whole arrays and subarrays still print each element on its own line, including in
-  mixed output lists; a final array adds no extra newline. INPUT only accepts a plain
-  identifier — no `INPUT arr[i]`.
+  mixed output lists; a final array adds no extra newline. INPUT accepts writable
+  scalar locations, including array elements, public record/class fields and
+  pointer dereferences, using the shared lvalue checks. Whole arrays and whole
+  records/classes remain unsupported INPUT targets.
 - **Arrays cross function boundaries only as parameters.** `ArrayTable` is scoped per
   function now, so referencing another function's array fails cleanly as
   "Undeclared array". Whole arrays pass as `ARRAY OF T` / `ARRAY[l:u,...] OF T`
@@ -49,8 +51,8 @@ test programs.
 - **File handling (§9.1) sharp edges.** `READ`/`WRITE`/`APPEND`/`RANDOM` are reserved
   keywords now — `DECLARE READ : INTEGER` no longer compiles. `WRITEFILE f, a, b` takes
   exactly two operands (the stray `, b` is a parse error).
-  READFILE's target must be a plain STRING variable — no CHAR, no `arr[i]` (mirrors
-  INPUT). The CIE guide's empty-line test `IF LineOfText = ""` compares contents.
+  READFILE's target must be a plain STRING variable — no CHAR, no `arr[i]`.
+  The CIE guide's empty-line test `IF LineOfText = ""` compares contents.
   At most 16 files open at once. All runtime misuse (not open, wrong mode, reopen,
   fopen failure, READFILE past EOF) throws an anonymous exception — guard reads with
   `WHILE NOT EOF(...)`. Caveat: the open-file table is keyed by the filename *string*
@@ -106,7 +108,7 @@ test programs.
 SET types (`SET`/`DEFINE` are reserved with dedicated errors),
 random files (OPENFILE...FOR RANDOM/SEEK/GETRECORD/PUTRECORD — TYPE is done, so these
 are unblocked now; the RANDOM keyword is reserved and gives a dedicated parse error),
-DATE, INPUT into array elements, string escape sequences,
+DATE, string escape sequences,
 array-typed record fields, whole-array RETURN, class methods/constructors/destructors,
 NEW and class inheritance. Compiler fixtures now live in `tests/` (see TESTING.md).
 Nightly CI runs the compiler suites, packaged EMBEDDED smoke checks and existing
diff --git a/doc/language/cpsc-language-overview.7.md b/doc/language/cpsc-language-overview.7.md
index 233e9ef..8838b7f 100644
--- a/doc/language/cpsc-language-overview.7.md
+++ b/doc/language/cpsc-language-overview.7.md
@@ -67,7 +67,7 @@ Closing and auxiliary keywords are documented with their main constructs: THEN/E
 
 # UNSUPPORTED FEATURES
 
-DATE, SET types and DEFINE, random-file operations (RANDOM/SEEK/GETRECORD/PUTRECORD), INT, RAND, INPUT into array elements or fields, string escapes, whole-array assignment or return, array fields, and class methods/constructors/destructors/inheritance (NEW/INHERITS/SUPER).
+DATE, SET types and DEFINE, random-file operations (RANDOM/SEEK/GETRECORD/PUTRECORD), INT, RAND, string escapes, whole-array assignment or return, array fields, and class methods/constructors/destructors/inheritance (NEW/INHERITS/SUPER).
 
 The individual pages note relevant differences from the Cambridge 2026 pseudocode guide. This manual describes the compiler's current support.
 
diff --git a/doc/language/keyword/cpsc-keyword-input.7.md b/doc/language/keyword/cpsc-keyword-input.7.md
index c1ec905..4c6c309 100644
--- a/doc/language/keyword/cpsc-keyword-input.7.md
+++ b/doc/language/keyword/cpsc-keyword-input.7.md
@@ -7,21 +7,38 @@ cpsc-keyword-input - read a value from standard input
 # SYNOPSIS
 
 ```text
-INPUT variable
+INPUT target
 ```
 
 # DESCRIPTION
 
-Read into a previously declared INTEGER, REAL, BOOLEAN, CHAR, or STRING variable. STRING input reads one whitespace-delimited word. The target must be a plain variable; array elements and record/class fields are unsupported, unlike the wider INPUT syntax in guide section 5.1.
+Read into an INTEGER, REAL, BOOLEAN, CHAR, or STRING location: a previously declared variable, an individual array element, or a public record/class field, as allowed by guide section 5.1. Nested fields, fields of array elements and pointer dereferences are supported through the existing access syntax. STRING input reads one whitespace-delimited word.
 
-Native C scalar variables are also supported, using their actual widths and signedness. Plain C char reads a character; signed/unsigned char read numbers. C _Bool reads a number and stores whether it is nonzero. C pointers, including C_STRING, cannot be INPUT targets. See [cpsc-keyword-c_type(7)](cpsc-keyword-c_type.7.md).
+Native C scalar targets are also supported, using their actual widths and signedness. Plain C char reads a character; signed/unsigned char read numbers. C _Bool reads a number and stores whether it is nonzero. C pointers, including C_STRING, cannot be INPUT targets. See [cpsc-keyword-c_type(7)](cpsc-keyword-c_type.7.md).
+
+The target address is evaluated once per INPUT execution, before reading the value. Array bounds, unset pointers and private fields are checked as for assignment. Constants, whole arrays, whole records/classes, enums and pointer values cannot be INPUT targets. A dereferenced pointer may select a supported target type.
 
 # EXAMPLE
 
 ```text
-DECLARE Name : STRING
-INPUT Name
-OUTPUT Name
+DECLARE Scores : ARRAY[1:3] OF INTEGER
+DECLARE j : INTEGER
+FOR j <- 1 TO 3
+    INPUT Scores[j]
+NEXT j
+OUTPUT Scores
+
+TYPE Student
+    DECLARE Score : INTEGER
+ENDTYPE
+CLASS Box
+    Value : INTEGER
+ENDCLASS
+DECLARE Person : Student
+DECLARE Item : Box
+INPUT Person.Score
+INPUT Item.Value
+OUTPUT Person.Score, ":", Item.Value
 ```
 
 # SEE ALSO
diff --git a/tests/FAILURES.md b/tests/FAILURES.md
index d88b850..dca0b8a 100644
--- a/tests/FAILURES.md
+++ b/tests/FAILURES.md
@@ -26,9 +26,11 @@ At baseline, both native and `-r` paths exposed the four i-group failures. All n
 
 Current exact command results are retained in `build/test-results`; the replay uses the original Actions SHA as its seed. Subsequent CI reports use their own explicit push SHA. Platform results from Actions are the authority for Windows/macOS verification; local Linux results do not establish their behavior.
 
+The `i/input-targets` and `iii/input-invalid-targets` cases cover INPUT into array elements and public record/class fields, including nested fields and pointer dereferences, with existing writable-location and type restrictions.
+
 ## Coverage gaps
 
-- Not implemented by the compiler, and not required to pass this initial suite: DATE, SET/DEFINE, random files, class methods/constructors/inheritance, INT/RAND, whole-array assignment and INPUT into array/record elements. Rejection of valid CIE syntax must not be relabeled as a successful negative test.
+- Not implemented by the compiler, and not required to pass this initial suite: DATE, SET/DEFINE, random files, class methods/constructors/inheritance, INT/RAND and whole-array assignment. Rejection of valid CIE syntax must not be relabeled as a successful negative test.
 - The guide's p. 14 pointer example points an INTEGER pointer at an enum; it conflicts with the project's explicit strict-pointee contract. Tests use matching pointees rather than silently choosing a new policy.
 - LCASE/UCASE are CHAR-to-CHAR in the guide (p. 17), while the project declares STRING results and also supports whole strings. Output observations cover case conversion but do not prove exact static return-type conformance.
 - No requirements are invented for unspecified integer overflow, REAL output spelling, out-of-range substring behavior, Unicode character semantics, or uninitialized CIE values. Native C ABI behavior is checked only against that platform's independent C++ reference.